Term
Two pet horses on a ranch are presented for extreme pruritus at their ventrum. The owners report the pruritus has gotten worse during the summer, and they notice increased numbers of small flying insects around at dusk and dawn. Examination of the horses reveals excoriations, alopecia, and thickening of the skin at the ventrum. One of the flies collected in the field by the owner is a small fly with mottled wings. What is your most likely diagnosis?
a) Tabanus fly bites
b) mosquito hypersensitivity
c) chrysops fly bites
d) Culicoides hypersensitivity
e) Onchocerciasis |
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Definition
| The correct answer is Culicoides hypersensitivity. Culicoides hypersensitivity is extremely pruritic and is also known as "sweet itch". Horses can be affected on their ventrum or dorsum, depending on the species of the fly. The horse develops a type 1 hypersensitivity to the flies' salivary antigens and develops excoriations, alopecia, and thickened skin as a result of scratching. The flies are more prevalent during the warmer seasons and are most active during dusk and dawn. Treatment includes controlling the fly population. Stabling the horses at dusk is often helpful because the flies rarely enter barns. Insecticides, stable blankets, and fans for circulating air in the stables may also be useful. The extreme pruritus and seasonality of the clinical signs is often enough to differentiate the Culicoides hypersensitivity from other skin diseases. Onchocerciasis is vectored by Culicoides, but is not seasonal and is not nearly as pruritic. Mosquitoes can be an annoyance and, more importantly, are vectors for more serious diseases such as the equine encephalitides. Tabanus flies and Chrysops flies cause pain to horses by lacerating them with their mouth parts to feed on their oozing blood. They do not cause pruritus and can be differentiated by their large, robust size. |
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Term
A 1.5 year old Hanoverian gelding presents for colic. He was dewormed yesterday with piperazine, and now he is behaving colicky. He also had a previous history of intermittent diarrhea. What is likely to have occurred that resulted in colic?
a) Infarction of the caudal mesenteric artery
b) Adverse reaction to piperazine in Hanoverians
c) Large die-off of ascarids resulting in impaction
d) small bowel bacterial overgrowth |
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Definition
| The correct answer is large die-off of ascarids resulting in impactions. Treatment with piperazine will result in rapid death of ascarids. If a horse has a large burden of worms, this may be contraindicated as they may die rapidly and result in obstruction, as most likely occurred in this case. There is no reported specific adverse reaction of piperazine in Hanoverian horses. Small bowel bacterial overgrowth is not an issue. This would not happen after treatment with piperazine, especially a day after treatment. Infarction of the caudal mesenteric artery is not seen with use of piperazine. |
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Term
Alpha 2 receptor agonist drugs are routinely used for sedation of horses. Which of the following alpha 2 receptor agonists has the lowest receptor affinity and shortest duration of action?
a) Ketamine
b) Romifidine
c) Detomidine
d) Xylazine
e) Medetomidine |
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Definition
| The correct answer is xylazine. Xylazine has the lowest receptor affinity, duration of action, and has the largest dose requirement of the alpha 2 agonists. Sedative effects of xylazine last for about 20 minutes. Sedative effects of detomidine typically last approximately 90 minutes; however, peak sedation is achieved for 10-20 minutes. Romifidine is similar to detomidine; however, the side effects are supposed to be decreased. Ketamine is a dissociative agent and not an alpha 2 agonist. |
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Term
An adult horse presents to you for recurrent seasonal pruritus during the summer months that seems to be worsening. On physical examination, you find multiple excoriations along the poll, mane, and tail. What is the most likely cause of this horse's pruritus?
a) Hypoderma
b) Habronema
c) Haematobia
d) Culicoides
e) Onchocerca |
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Definition
| The correct answer is Culicoides. Culicoides hypersensitivity, also referred to as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatitis can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Habronemiasis is a condition where the larvae of the stomach worm migrate and emerge creating granulomatous lesions, usually around the eye, male genitalia, or lower extremities. Inside the granulomas, you can find dead larvae. Haematobia irritans is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions, rather than more diffuse lesions caused by Culicoides. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often, lesions are diamond shaped and there may be a "bull's eye" lesion on top of the head. Onchocerca is nonseasonal, in contrast to Culicoides hypersensitivity, and variably pruritic. Ocular lesions can also occur with Onchocerca including uveitis, conjunctivitis, and keratitis. Lastly, Hypoderma is also a bigger problem in cattle but can occur in horses and typically creates nodules on the dorsum that have a pore on top. |
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Term
Fistulous withers refers to inflammation of the ____________.
a) Infraspinatus
b) Supraspinous bursa
c) Bicipital bursa
d) Nuchal ligament |
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Definition
| The correct answer is supraspinous bursa. This bursa is variable in size and location but is usually found between the second and fifth thoracic vertebrae and can extend ventrolaterally to the margin of the scapular cartilage. The etiology is thought to be infectious. Clinical signs are pain, heat, and swelling in the region of the bursa. After days to weeks, the bursa can rupture resulting in drainage of fluid. Brucella abortus has been identified in up to 80% of clinical cases by serology and culture. Treatment consists of flushing the fistula and appropriate antibiotics. |
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Term
Endotoxemia is a term applied when an animal exhibits multiple adverse clinical signs including one or more of the following: fever or hypothermia, leukopenia, tachycardia, tachypnea, obtundation, and a change in gut motility. These physiologic effects are caused by what?
a) An adverse reaction to aspirin, phenylbutazone or other NSAIDS
b) Bacterial lipopolysaccharide
c) cell wall components of Gram positive bacteria
d) Exotoxins from clostridial organisms
e) DNA from Gram negative bacteria |
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Definition
| The cell walls of all Gram negative bacteria contain varying amounts of lipopolysaccharide, which in turn varies in its potency to create adverse reactions in animals. The signals have evolved on monocytes and macrophages to warn the animal when a Gram negative bacterium has gained access. When the reaction to this signal is overzealous, a cascade of adverse physiologic reactions can occur. |
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Term
A 3 month old foal presents to you with a cough. On your exam, you note that the horse has a respiratory rate of 50, temperature of 103 F (39.4 C), and has wheezes on auscultation. You also note abdominal tucking on inspiration. You perform a transtracheal wash and find gram positive pleomorphic rods on cytology. What is your diagnosis?
a) Rhodococcus ( Corynebacterium) eui
b) Streptococcus equi ssp. Zooepidemicus
C) Equine influenza
d) Streptococcus equi ssp.equi |
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Definition
| The correct answer is Rhodococcus (Corynebacterium) equi. The signalment and clinical signs are most consistent with Rhodococcus equi infection. The pleomorphic gram positive rods on cytology make this clearly the best choice. The pleomorphic rods of Rhodococcus are often said to look like Chinese letters, so keep this in mind if you are shown cytology on the exam. Another helpful diagnostic tool is the presence of single or multiple abscesses within the lung fields observed via thoracic radiography or ultrasonography. |
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Term
A 14-year old 500 kg multiparous mare presents for a 3 hour history of moderate to severe colic. Her current foal is 2 weeks of age. Upon physical examination the mare is uncomfortable with a heart rate of 70 beats/min, respiratory rate of 16 breaths/min and rectal temperature of 98.4F (36.9 C). A nasogastric tube is placed with no net gastric reflux obtained. A large gas filled section of intestine is noted on rectal examination. You administer 5 mg of detomidine IV which provides only brief sedation. Based on this limited information, what is the most likely cause of these clinical signs?
a) Large colon impaction
b) Large colon volvulus
c) small intestinal entrapment within the epiploic foramen
d) Hemorrhage from rupture of the uterine artery post-foaling
e) small intestinal strangulation |
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Definition
The correct answer is large colon volvulus. Typically, horses with this problem demonstrate rapid onset of severe unrelenting pain and often occurs in postpartum broodmares. Gas distension of the colon may be significant and result in respiratory compromise because the distended colon presses on the diaphragm. Gastric reflux may not be present as the small intestine may not be obstructed in this process.
This is a surgical emergency; if surgery or necropsy is performed, the volvulus is typically located at the mesenteric attachment of the colon to the dorsal body wall. Because of the rapid onset, the prognosis is guarded to poor in many cases. |
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Term
Calculate the extracellular volume of a 450kg horse.
a) 300L
b) 270 L
c) 180L
d) 90L
e) 45L |
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Definition
The correct answer is 90L. Total body water is 60% of body weight. Extracellular fluid is approximately 1/3 of total body water, therefore
450kg x .6 = 270L total body water
270L x .33 = 89.1L ECF.
ECF is composed of plasma, interstitial fluid and transcellular lymph such as CSF and synovial fluid. |
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Term
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Definition
| The most likely cause of the epistaxis based on the radiographs is ethmoid hematoma. These lesions are angiomatous masses that originate from the mucosal lining of the ethmoid conchae or walls of the maxillary or frontal sinus. Guttural pouch mycosis also can result in epistaxis but typically has no radiographic changes. Although horses can get tumors in the nasal passages, this is relatively rare. Exercise-induced pulmonary hemorrhage also can result in epistaxis, but the blood originates from the lungs. In the radiograph provided, notice the smooth, well-defined soft tissue mass in the sinus region of this horse. No osseous changes or fluid lines are apparent in this radiograph. In this particular case (ethmoid hematoma), the soft tissue mass is actually dorsal to the ethmoid turbinates (ethmoids are normal appearance in this case). Upon surgical removal, a definitive diagnosis of ethmoid hematoma was confirmed. |
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Term
What body systems are most affected in an anaphylactic reaction in a horse?
a) lungs and colon
b) liver and kidneys
c) kidney and colon
d) heart and small intestine
e) Liver and lungs |
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Definition
| The correct answer is lungs and colon. These are referred to sometimes as the shock organs in the horse. When a horse undergoes an anaphylactic reaction from an allergen or chemical stimulus, the primary signs will be respiratory and lower GI and will include dyspnea or severe respiratory distress and diarrhea. Other common signs include anxiety, tachycardia, piloerection, and sweating. Treatment of anaphylactic shock usually includes injection with some combination of epinephrine, corticosteroids, and an antihistamine. |
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Term
| Treatment of anaphylatic shock |
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Definition
| epinephrine, corticosteroids, and an antihistamine |
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Term
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Definition
| osteoarthritis of the distal intertarsal joint and/or tarsometatarsal joint. |
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Term
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Definition
| synovial distention of the tarsocrural joint |
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Term
While examining the blood smear from a horse, you detect multiple intracytoplasmic inclusion bodies inside the neutrophils that appear as aggregates of round dark purple dots. What do you suspect these indicate?
a) Borrelia Burgdorferi
b) Anaplasma phagocytophilum
c) Neorickettsia risticii
d) Herpesvirus type 3 |
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Definition
| The correct answer is Anaplasma phagocytophilum (previously known as Ehrlichia equi). Anaplsama phagocytophilum infection can cause morulae to be present in neutrophils and eosinophils. Neorickettsia risticii (Potomac horse fever) can cause morulae in monocytes but these are rarely seen on blood smears. Borrelia organisms are not seen in peripheral blood and herpes inclusion bodies are intranuclear and would not be seen in a blood smear. |
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Term
If you palpate a mare for pregnancy at day 30, what structure are you feeling for?
a) Enlarged uterine artery
b) ovarian location
c) fetus
d) chorionic vesicle |
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Definition
| The correct answer is chorionic vesicle. At this early in pregnancy, the other structures would not be located. A fetus does not become palpable until about 90-120 days. Ovary location and enlarged uterine arteries are not palpably changed until 7 months of pregnancy. |
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Term
| Normal synovial fluid analysis |
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Definition
| Total Protein < 2.5 gm/dL, Total Nucleated Cell Count < 500 cells/mcL, Cytology primarily (> 90%) mononuclear cells. |
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Term
An 11-month old Paint gelding is presented to you for symmetric ataxia, weakness, and spasticity of all limbs. When walking, the hind limbs frequently interfere with one another. Based on the signalement, history, and physcial examination findings, you suspect equine degenerative myeloencephalopathy (EDM). What diagnostic test would you use to support your suspicion?
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Definition
| There is no definitive antemortem test for EDM; it can only be confirmed through histopathologic examination of the spinal cord and brainstem and the identification of diffuse neuronal fiber degeneration of the white matter. However, many cases of EDM have been associated with low serum vitamin E concentrations, so measurement of vitamin E is suggestive of disease. The exact etiology of EDM is unknown, however, oxidative stress and damage to the central nervous system is a prominent theory. |
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Term
How long after parturition in the mare is a placenta considered to be retained?
a) 3-6 hours
b) 20-30 minutes
c) 1-2 hours
d) 24-36 hours
e) 48 hours |
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Definition
| The correct answer is 3-6 hours, although controversy exists in the literature on the exact time-line in which fetal membranes are considered retained. The placenta of a horse should be expelled in the time frame between 30 minutes and 3 hours or else corrective measures should be taken, such as oxytocin administration to prevent metritis and infection from occurring. Retained placenta is a serious condition in mares and should be evaluated as soon as possible. Associated complications of retained placenta include metritis and laminitis. Unlike other species, the mare does not eat the placenta. |
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Term
Which of these vaccines administered intramuscularly is most likely to cause a local reaction at the injection site of a horse?
a) Tetanus antitoxin
b) Rhinopneumonitis
c) Rabies
d) Strangles |
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Definition
| Historically, an intramuscularly administered Strangles vaccine has been available and has been associated with soft tissue reaction. More recently, an intranasal vaccine has become available, which is associated with local protection without any injection reaction. |
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Term
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Definition
| Xylazine has the lowest receptor affinity, duration of action, and has the largest dose requirement of the alpha 2 agonists. Although xylazine will provide the shortest duration of action, clinicians are told to be careful when using xylazine and working with the hind limbs because these horses can have a sudden rapid limb movement known as a phantom kick. Sedative effects of xylazine last for about 20 minutes. Sedative effects of detomidine typically last approximately 90 minutes; however, peak sedation is achieved for 10-20 minutes. Romifidine is similar to detomidine; however, the side effects are believed to be decreased. |
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Term
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Definition
| The physical exam findings are consistent with the most common equine arrhythmia encountered, atrial fibrillation. Ideally, you would begin oral dosing of quinidine via a nasogastric tube at 2 hour intervals until there is conversion or toxicosis. An increase in the QRS duration of greater than 25% as compared to before initiation of treatment is considered a sign of toxicity. Clinical signs of toxicosis include colic, ataxia, hypotension, diarrhea, and edema. Digoxin will not convert an atrial fibrillation to a normal rhythm. However, it is indicated as adjunctive therapy when the vagolytic effect of quinidine causes a significant acceleration in ventricular response rate, the resting heart rate is in excess of 90 beats per minute, if the horse is exhibiting a low vagal tone, or if conversion has not been achieved within 24 hours of initiating quinidine therapy. This horse is probably not in congestive heart failure given the exam findings and will not benefit from the use of diuretics. A precordial thump is ineffective, and defibrillation is only indicated during ventricular fibrillation, not atrial. Usually, there is an excellent prognosis for conversion if the horse has a heart rate of less than 60 beats per minute, atrial fibrillation of less than four months duration, and if there is a murmur less than or equal to a grade 3/6. Recently, novel therapies that have been used for atrial fibrillation in horses include amiodarone, flecainide, and transvenous electrical cardioversion. However, quinidine still remains the most commonly used drug, despite its potential toxic side effects. |
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Term
| when is defibrillation indicated? |
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Definition
| during ventricular fibrillation |
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Term
A club foot in a horse is a result of ____________.
a) Deep digital flexor tendon contracture
b) Deep digital flexor tendon rupture
c) Superficial digital tendon contracture
d) superficial digital tendon rupture |
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Definition
| The correct answer is deep digital flexor tendon contracture. There are multiple causes for flexural deformity of the distal interphalangeal joint (deep digital flexure contracture) including rapid bone growth, excessive feeding, faulty nutrition and lack of exercise. The distal check ligament controls the stretch in the long tendon of the deep digital flexor. If this becomes functionally too short, flexion of the interphalangeal joint occurs, resulting in a club foot. If medical therapy is not successful, surgical correction is recommended. |
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Term
An adult horse presents to you for crusting lesions along the ventral midline. The lesions are relatively not pruritic and are very round and focal. What is the most likely cause of these lesions?
a) Culicoides
b) hypoderma
c) habronema
d) haematobia
e) onchocerca |
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Definition
| The correct answer is Haematobia. Haematobia irritans is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions, rather than more diffuse lesions caused by culicoides. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often lesions are diamond shaped, and there may be a ""bull's eye"" lesion on top of the head. Onchocerca is nonseasonal, in contrast to culicoides hypersensitivity, and variably pruritic. Ocular lesions can also occur with Onchocerca including uveitis, conjunctivitis, and keratitis. Culicoides hypersensitivity, also referred to as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatitis can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Habronemiasis is a condition where larvae of the stomach worm that emerge from flies feeding on pre-existing wounds or genitalia or eyes, then migrate into the tissue and cause a granulomatous reaction. Inside the granulomas, you can find dead larvae. Lastly, Hypoderma is a bigger problem in cattle but can occur in horses and typically creates nodules on the back that have a pore on top. |
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Term
A healthy race horse with a heart rate of 16 bpm is most likely to have what electrical rhythm finding?
a) Third degree av block
b) second degree av block
c) a fib
d) ventricular premature complexes |
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Definition
| The correct answer is second-degree atrioventricular block. First-degree and second-degree atrioventricular blocks are considered a normal finding in horses and usually result from high vagal tone. All other answer choices are abnormal findings and should be addressed accordingly. Atrial fibrillation is usually treated with quinidine. A chronic third-degree atrioventricular block can be treated by placing a pacemaker. If the onset is rapid then a catecholamine or parasympatholytic such as atropine may be used. |
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Term
Which of the following conditions is most likely to cause an elevated level of serum bilirubin in a 7-year old horse?
a) Acute myopathy
b) Renal failure
c) Hemolytic anemia
d) hypokaelemia
e) Metabolic acidosis |
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Definition
| Hemolysis results in an increase in bilirubin (mainly the unconjugated form) as the damaged red blood cells are removed and the hemoglobin is processed through the liver. Of course, liver disease with failure can also cause elevated bilirubin. In liver disease, both the conjugated and unconjugated forms are elevated. |
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Term
Which of these parasites causes granulomatous skin lesions that often contain small calcified dead larvae inside?
a) Habronema
b) culicoides
c) onchocerca
d) haematobia |
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Definition
| The correct answer is Habronema. Habronemiasis is a condition where the larvae of the stomach worm migrate and emerge, creating granulomatous lesions, usually around the eye, male genitalia, or lower extremities. Inside the granulomas, you can find dead larvae. Culicoides hypersensitivity, also referred to as sweet itch, occurs due to allergy to the saliva of the gnat. It recurs seasonally in the warmer months and tends to worsen with age. Typically, horses are pruritic and develop lesions on the poll, mane, and tail from self trauma, although ventral midline dermatitis can occur as well. More chronically, scarring can occur. Treatment is to decrease exposure to the gnat and to treat with steroids. Haematobia irritans is a bigger problem in cattle than horses (they reproduce in cow feces) but can affect horses, especially ones that are near cattle. It typically causes ventral midline dermatitis with wheals with a central crust that progress to alopecia and ulceration with fairly focal lesions. Onchocerca can cause dermatitis in the horse due to hypersensitivity to dying microfilariae. Lesions include alopecia and scaling of the ventral midline, face, and pectoral region. Often lesions are diamond shaped, and there may be a ""bull's eye"" lesion on top of the head. |
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Term
Which nerve block would be most specific for alleviating pain associated with laminitis?
a) suspensory ligament block
b) palmar digital block
c) abaxial sesamoid block
d) high 4 point block |
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Definition
| The correct answer is the abaxial sesamoid block. The four basic blocks used by equine clinicians are the palmar digital, abaxial sesamoid, low four point and high four point block, each desensitizing more of the limb as your blocks move more proximal on the limb. The palmar digital desensitizes the palmar third of the foot whereas the abaxial sesamoid desensitizes the entire foot. As laminitis is associated with separation of the dorsal lamina, the abaxial sesmoid block would be most likely help with laminitis. Of note, desensitizing the foot during acute laminitis is not typically employed as a standard treatment but is rather used to help alleviate pain so that the clinician can perform radiographs of the feet or trim the feet. The low 4 point block desensitizes the palmar aspect distal to the distal end of the second and fourth metacarpals. The high 4 point block desensitizes the leg distal to the carpus or tarsus. The suspensory ligament block desensitizes the deep branch of the lateral palmar nerve at the level of the carpometacarpal joint. |
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Term
| You are examining a 7-year old Thoroughbred gelding for a 5-day history of anorexia and jaundice. Which of the following enzymes would you consider to be liver specific in the horse? |
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Definition
You have to read the possible answers carefully in this question and recall which enzymes are liver-specific in the horse. In this instance, SDH and GGT are both liver-specific; SDH is found in the liver of all animals. An increase in serum SDH concentration suggests hepatocellular injury. Elevation in serum GGT is predominately associated with biliary epithelial cells and is also liver-specific.
The other enzymes listed may be increased with liver disease but may also arise from bone (ALP) or muscle (ALT, AST). |
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Term
| An 8-year old Thoroughbred gelding was presented for acute onset of trembling, excessive recumbency, constant shifting of body weight while standing, and muscle atrophy. The horse is housed in a dry lot with no pasture availability. Diet consists of moderate quality grass hay and sweet feed. The CBC is normal with abnormalities on biochemistry analysis including mild elevation in creatine kinase (CK) and aspartate aminotransferase (AST). Cerebrospinal fluid (CSF) analysis shows no remarkable findings. Based on this information, what disease process do you suspect? |
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Definition
| The correct answer is EMND, equine motor neuron disease. This is a neurologic disease associated with dietary vitamin E deficiency which is believed to contribute to oxidative damage to the CNS. However, the precise pathophysiology is unknown. Retrospective studies have noted that horses with EMND are commonly housed on dry lots with little to no availability to pasture or good quality hay (perhaps contributing to low blood vitamin E concentrations). The clinical signs in this question are classic for EMND whereas horses afflicted with the other options do not typically demonstrate trembling or shifting of body weigh |
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Term
| What is the most common cause of colic in a newborn foal? |
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Definition
| The correct answer is meconium impaction. Meconium impaction occurs in the rectum or small colon. Clinical signs include straining, swishing of the tail, and restlessness. Rectal examination reveals numerous hard fecal balls. Treatment consists of an enema with water and a mild soap. Meconium is the first intestinal discharges of the newborn foal, consisting of epithelial cells, mucus, and bile. |
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Term
| A mare in the last month of gestation develops ventral edema from the udder to the xiphoid. She then becomes acutely painful and tachypneic and does not want to ambulate. What condition did the mare experience? |
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Definition
| The correct answer is ruptured prepubic tendon. This tendon courses along the ventrum and provides the major support for all the structures in the equine abdomen. It can rupture in late pregnancy, especially in obese draft mares. This is usually preceded by ventral swelling. If such swelling is noted, preventative measures should be taken such as restricting activity and possibly slinging the abdomen to provide support. This condition is very painful to the mare and may affect the ability to increase intra-abdominal pressure during parturition. Assisted parturition by a veterinarian should be strongly considered. A body wall hernia may also result in similar signs as a ruptured prepubic tendon. |
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Term
Treatment of choice for splints (intraosseous desmitis) includes which of the following?
a) arthrodesis
b) local steroid injection
c) antibiotics
d) Rest and NSAIDS |
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Definition
| The correct answer is rest and NSAIDs. Splints or intraosseous desmitis is inflammation of the intraosseous ligament between the 3rd metacarpal (or metatarsal) bone with the small metacarpal (or metatarsal) bones. Periostitis occurs with new bone formation along the splint bones or small metacarpals (or metatarsals) usually due to repetitive concussion, excessive training, poor conformation, or improper shoeing. Radiographs are necessary to distinguish this condition from fractures of the splint bones. |
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Term
You are examining a 3-year old Thoroughbred gelding for lameness of the right forelimb. The lameness persists with a palmar digital and abaxial sesamoidian nerve block but is improved by 90% after a low 4-point (low palmar) nerve block. The source of the lameness is likely in which region of the limb?
a) proximal suspensory ligament
b) carpal-metacarpal joint
c) Metacarpophalangeal joint
d) Third phalanx |
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Definition
| The low 4-point (low palmar) nerve block typically provides local anesthesia to the metacarpophalangeal (fetlock) joint and below. An injury to this area is most likely. The proximal suspensory ligament and carpal-metacarpal joint would require local anesthesia more proximally. |
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Term
A 2-year old Quarter Horse presents for intermittent muscle fasciculation followed by weakness. What condition should you suspect?
a) Hyperkalemic periodic paralysis
b) Grass tetany
c) Myotonia
d) Stringhalt |
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Definition
| The correct answer is hyperkalemic periodic paralysis (HYPP). HYPP is seen in Quarter Horses due to a point mutation in a key part of a skeletal muscle sodium channel subunit. This results in elevation of the resting membrane potential to increase the likelihood of depolarizing. Excess concentrations of potassium can result in failure of the sodium channels to inactivate. Therefore, treatment is directed at decreasing dietary potassium. |
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Term
12 L of gastric reflux with a pH of 6.5 in a horse is most indicative of which of the following?
a) normal finding
b) gastric ulceration
c) obstruction
d) colon displacement |
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Definition
| The correct answer is obstruction. A pH that is greater than 5 suggests that small intestinal contents are refluxing into the stomach, resulting in an increased pH. Small intestinal ileus is another differential but was not an answer choice. |
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Term
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Definition
| The correct answer is strangulating lipoma. Lipomas are a common cause of small intestinal obstruction in older horses. Typically, a section of the small intestine becomes intertwined with a pedunculated lipoma, resulting in obstruction and possible devitalization of the small intestine. Surgical correction is necessary to correct this problem. None of the other answer choices typically result in the clinical signs described, particularly gastric reflux. Left dorsal colon displacement typically have milder clinical signs, and the diagnosis can be made by rectal palpation and ultrasonography. |
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Term
Which condition is associated with apical fracture of the proximal sesamoid bones, avulsion fractures of the palmar aspect of the third metacarpal bone, or fractures of the distal third of the small metacarpal bones in horses?
a) sweeney
b) superficial digital flexor tendonitis
c) deep digital flexor tendonitis
d) Suspensory ligament desmitis |
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Definition
| The correct answer is suspensory ligament desmitis. The presence of these fractures would indicate ultrasonography as the next diagnostic test to evaluate for suspensory ligament desmitis, since these fractures are present with this condition 25% of the time. |
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Term
| Auricularpalpebral nerve block |
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Definition
The auriculopalpebral nerve is a branch of the facial nerve and is therefore motor only. The auriculopalpebral block is useful in providing eyelid akinesis by blocking motor innervation primarily to the orbicularis oculi, thereby allowing manipulation of the eyelids without putting pressure on an already painful eye. This block is motor only and does not provide any desensitization.
The supraorbital/frontal nerve block can be used to block a branch of the ophthalmic division of the trigeminal nerve, desensitizing the middle two-thirds of the upper eyelid and forehead skin. It may also provide some motor block of the levator palpebrae superioris due to a branch of the oculomotor nerve which runs adjacent. |
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Term
| During a routine pre-purchase exam of a 24 year old Peruvian Paso, a harsh and decrescendo holodiastolic 3/6 murmur is auscultated with a point of maximum intensity at the left base of the heart. There were no other abnormal physical exam findings. What is the most likely diagnosis best on clinical exam and prognosis of this horse? |
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Definition
| The correct answer is this horse most likely has aortic regurgitation due to degeneration of the aortic valve and should have no impact on performance. Given the location of the murmur and signalment, this should be the logical answer to choose. The thing you need to know is that aortic regurgitation in the horse is usually a degenerative change and there isn't much that can be done about it. Horses are rarely impaired by development of the murmur. In a true pre-purchase exam, you would be wise to recommend a full cardiac work-up to definitively diagnosis the source of the heart murmur. The potential buyer may decline further diagnostics, but at least you will have offered the choice and have provided the proper information to the client. |
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Definition
| Anaplasmosis (formerly Ehrlichi equi) infects primarily neutrophils and form inclusion bodies which consists of one or more coccobacillary organisms within these cells, known as morula. The complete pathogenesis of this disease is not fully elucidated but the organism is spread via tick bites. Other clinical signs that may be associated with this disease include petechiation, icterus and ataxia. The drug of choice for this disease is...(think about it for a second)...you got it...oxytetracycline. |
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| Horse with navicular disease- what to shoe? |
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Definition
The case describes a horse with navicular disease. Pain from navicular disease can be reduced by a shoe that elevates the heel.
Palmar foot pain can be the result of pain from any number of structures including the navicular bone, navicular suspensory or deep digital flexor tendon, navicular bursa, or several other heel areas. Navicular disease is a term used for pain associated with any of these structures. |
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A 3 month old filly presents with a non-painful soft swelling in the right parotid region. She is very bright and alert and has a normal physical examination with the exception of a slightly stertorous breathing. What is the most likely diagnosis?
a) guttoral pouch mycosis
b) streptococcus equi
c) guttoral pouch tympany
d) ruptured longus capitis |
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Definition
The correct answer is guttural pouch tympany. Guttural pouch tympany is a condition where the pouch becomes distended with air. It is thought to be due to a defect in the Eustachian tube or pharyngeal tissues. It leads to a characteristic non-painful, air-filled swelling and is treated by fenestrating the membrane between the normal and affected pouch.
In an animal this young, guttural pouch mycosis is unlikely, and the most common clinical sign of mycosis is epistaxis or dysphagia. A ruptured longus capitis occurs from trauma and causes severe hemorrhage from the guttural pouch rather than the swelling described. Streptococcus equi ssp. equi usually affects animals of 1 year of age or older, and usually causes swelling of lymph nodes. It can lead to guttural pouch empyema, but that is less likely given the signalment and presentation of this animal. |
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Term
| Which of these findings are most consistent with a diagnosis of chronic obstructive pulmonary disease in the horse? |
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Definition
| The correct answer is end expiratory wheezes. In chronic obstructive pulmonary disease (COPD), airway diameter is reduced by inflammatory exudate, edema, and bronchoconstriction. As lung volume decreases during expiration, the narrowed bronchioles collapse shut (dynamic airway collapse). This traps air distal to the closure and creates the wheezes heard as the airways narrow towards the end of expiration. |
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| A 2-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 3 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Radiographs show no evidence of new bone formation in the fetlock. You diagnose the horse with osselets (periostitis of the distal dorsal cannon bone). What is the best treatment recommendation? |
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Definition
Cases of osselets that are caught before the development of osteoarthritis often respond completely to medical management consisting of rest, anti-inflammatories (such as phenylbutazone) and intra-articular injections of sodium hyaluronate or polysulfated glycosaminoglycans (Adequan).
Fetlock arthrodesis is reserved for more advanced fetlock injuries. Deep digital flexor tenotomy is used to treat certain cases of chronic laminitis. Palmar digital neurectomy is used to treat navicular disease and results in desensitization of the heel. |
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Term
| Which of the following is not known to classically cause crusting dermal lesions on horses? |
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Definition
| The correct answer is Corynebacterium pseudotuberculosis. Corynebacterium pseudotuberculosis is also known as pigeon fever. It causes an ulcerative lymphangitis and abscesses in the pectoral region of horses. Treatment is aimed at hot packing the swellings and draining the abscesses. Antibiotics can be administered but have been known to prolong the disease by delaying abscess formation. The other four answer choices classically present as crusting dermal lesions on horses. |
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Definition
| Aspergillus is the most commonly identified fungal pathogen in guttural pouch mycosis. While this disease can present with epistaxis, dysphagia is sometimes a presenting complaint. Remember, cranial nerves IX, X, XI, and XII travel through the pouch and may be damaged from mycotic lesions, thus resulting in dysphagia. If you are unfamiliar with endoscopic images of the equine guttural pouch, the mycotic lesion is seen from approximately 1 to 7 o'clock while the stylohyoid bone is evident in the left side of the image. |
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Term
Which of these is the most useful indicator of whether anemia in a horse is regenerative or not?
a) Bone marrow examination
b) Reticulocyte count
c) Degree of anisocytosis
d) Mean cell volume |
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Definition
| The correct answer is bone marrow examination. In horses, reticulocyte counts are not useful because horses don't release reticulocytes into circulation. Red blood cell indices such as mean corpuscular volume and anisocytosis may be altered in a regenerative response, but the only accurate way to gauge response to anemia in a horse is with bone marrow examination or serial CBCs taken daily for many days. |
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| A horse is suspected of having the muscle disease rhabdomyolysis, and you are seeking a laboratory test to help confirm the diagnosis. Of the following, which test would likely be the most helpful? |
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Definition
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Term
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Definition
| The correct answer is Chorioptes equi. Chorioptes is a mange mite that is usually found around the foot and fetlock. It causes a pruritic dermatitis that can cause the formation of papules, crusts, thickened skin, as well as alopecia. The mites are often found in the feathered hair around the fetlocks of draft horses. As with other mites, ivermectin is the treatment of choice. Culicoides, Haematobia irritans (the Horn fly) and onchocerciasis often cause dermatitis at the ventral midline of horses. |
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Term
| You are an equine clinician working out in the field. You encounter a colic case and palpate a small intestinal obstruction. You decide to refer the case to a nearby hospital for surgical intervention. What is the most important thing to do before shipping the horse? |
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Definition
pass a nasogastric tube
It is crucial to do this, as horses are unable to vomit due to high lower esophageal sphincter tone. By passing the tube, you will allow reflux and relieve life-threatening gastric pressure. Sedation is important to help provide relief; however, gastric rupture will kill the horse first. |
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| A 5 year old Standardbred from the east coast presents for progressive ataxia. On physical exam, there are areas of muscle loss noted around the left gluteal region of the horse. A neurologic exam revealed knuckling over on all four limbs, stumbling of limbs when walked in a circle, and a dysmetric gait. Given these clinical signs what is the most likely differential? |
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Definition
| The correct answer is equine protozoal myeloencephalopathy. If at any time you observe vague asymmetric/multifocal neurologic clinical signs with focal muscle atrophy, this disease should be your top differential. Other potential clinical signs include hyporeflexia, spasticity, localized areas of sweating, cerebellar signs, head tilt, facial paralysis, circling, dysphagia, and blindness. EPM is caused by Sarcocystis neurona which is a protozoal organism that migrates randomly through the spinal cord and brain. This will result in damage of both white and gray matter. Cauda equina neuritis is an inflammation of the nerve roots (usually the cauda equina but sometimes cranial nerves) which results in lower motor neuron signs. You may see paresis and paralysis. Clinical signs include chewing the tail head, hypotonic anus, fecal retention, urinary incontinence (see urine scalding of the thighs), and hindlimb ataxia. Unfortunately, there is no good treatment. There are two forms of cervical vertebral stenotic myelopathy (aka Wobbler Syndrome). One form is called cervical vertebral instability. In this case, ventroflexion of the neck results in spinal cord compression. Most commonly affected sites are C3-4 and C4-5. The other form is known as cervical static stenosis. In this case, the compression is continuous regardless of the neck position. Clinical signs are usually in the form of a wide based stance, conscious proprioceptive deficits, ataxia, paresis, and spasticity which is worse in the hindlimbs. Verminous myelitis results from aberrant migration of parasites through the central nervous system. Clinical signs are very similar to that of EPM. However, EPM occurrence is much more common. Parasites known to undergo aberrant migration in the horse are Strongylus vulgaris, Micronema deletrix, Draschia megastoma, and Setaria spp. |
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Term
Which of the following causes liver failure when ingested by horses?
a) Bracken fern
b) oleander
c) fiddleneck
d) Astragalus |
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Definition
| The correct answer is fiddleneck. Fiddlenecks contain pyrrolizidine alkaloids as does groundsel, ragwort, and senecios. Pyrrolizidine alkaloids cause secondary photosensitization as well as hepatic damage that are cumulative and progressive. Treatment consists of supportive care for liver failure and prognosis is poor. |
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Term
You examine a one-week old female foal for eye problems. She has mild blepharospasm and epiphora. On ocular exam, you note that the lower eyelid margin is inverted inward. What is the usual treatment for this condition?
a) Surgical correction of the defect
b) No treatment is necessary
c) Enucleation
d) Place a patch over the eye |
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Definition
| The correct answer is no treatment is necessary. Entropion in foals is fairly common and will usually resolve spontaneously. Surgical correction is reserved for cases that do not resolve, because over correction in a young animal could result in further eyelid defects as the foal grows. If clinical signs are severe enough, a procedure where local anesthetic is infused and the eyelid is everted and stapled can be performed as a temporary fix until the problem resolves. Enucleation or patching of the eye are not indicated. |
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Term
| A 4 year old horse presents to you with a mucopurulent nasal discharge, lethargy, and depression. On physical exam, the horse has a temperature of 103.7F (39.8 C) and has markedly enlarged mandibular and retropharyngeal lymph nodes. You suspect that the horse has strangles. What would you expect to see if you aspirated one of the enlarged lymph nodes? |
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Definition
| The correct answer is purulent inflammation and gram positive cocci with large capsules. The causative agent of strangles is streptococcus equi ssp. equi which is a gram positive cocci with a large capsule. It causes suppurative abscessation and enlargement of the mandibular and retropharyngeal lymph nodes. |
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Term
If a patient exhibits a head tilt to the right, circling to the right, and has normal strength, what type of lesion does it have _______.
a_ left side: central vestibular dysfunction
b) Right side peripheral VB
c) Left side: peripheral VB
d) Right side: central VB |
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Definition
| The correct answer is right side, peripheral vestibular dysfunction. Peripheral vestibular dysfunction causes signs of head tilt, nystagmus, circling and asymmetric ataxia with preservation of strength. The head tilt is toward the affected side as is circling towards the lesion. Comparatively, central vestibular disease has similar clinical signs but general conscious proprioceptive deficits, weakness and cranial nerve deficits may also be present along with depression. |
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Term
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Definition
Strangles can be a difficult disease to control and vigilant preventative measures are necessary to minimize transmission as a small percentage of horses develop persistent infection of the guttural pouches associated with purulent inflammation or the presence of chondroids. These carriers can be detected either by culture or by detection of S. equi DNA using the polymerase chain reaction (PCR) test. PCR is a more sensitive test but also more expensive and may have false positives in recently infected horses due to residual DNA from dead bacteria.
Investigation of carriers should be done either before a new animal is introduced into a stable or herd, or at least 30 days following recovery of a horse from strangles. Animals should be isolated until there have been 3 consecutive weekly negative cultures and/or PCR reactions.
If an animal is positive, endoscopic evaluation of the guttural pouch is recommended, chondroids removed, and guttural pouches treated by flushing and infusing 5 million units of penicillin G in 3% gelatin. In addition, these horses should be treated with penicillin G intramuscularly for 7 days, isolated for 30 days, and then retested with the 3 consecutive series of nasopharyngeal swabs and culture.
You should note that even this diligent recommendation is not 100% fail-safe. However, this is still the best answer choice. It is not true that most horses become lifelong carriers as this applies to <10% of horses. Waiting 90 days after resolution without testing or retreating is not recommended.
Vaccines against S. equi are available; there are intramuscular and intranasal vaccines available. The intramuscular vaccine is associated with pain and abcessation at the vaccine site as well as purpura hemorrhagica. The killed vaccine does not provide complete protection but it does reduce the severity of clinical illness. A live, attenuated S. equi vaccine has been introduced as an intranasal vaccine for the prevention of strangles. It is strongly recommended that other vaccines or injections not be administered at the same time as the intranasal vaccine. Since the live organism may persist in the nose, control measures that involve detection of carriers may not be effective in horses immunized with this vaccine.
Serology is best for determining the exposure status of a horse and is mainly used to aid in the diagnosis of purpura hemorrhagica and bastard strangles. |
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Term
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Definition
| A 3rd degree burn involves the epidermis, dermis, and adnexal structures. Alternatively, a 1st degree (superficial) burn involves the epidermis only; a 2nd degree (partial thickness) burn involves the epidermis and may go down to the deep dermis. 4th degree burns involve total destruction of the skin, fat, fascia, bone and muscle. This classification scheme would generally apply to all animals, not just horses. |
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Term
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Definition
| The correct answer is laryngeal hemiplegia. In this condition, the recurrent laryngeal nerve is damaged. Interestingly, the left side is almost always the side that is affected. An actual cause is usually not found, although direct trauma and certain toxins can cause laryngeal hemiplegia. It is thought to be a hereditary disorder. An intrathoracic large airway obstruction and asthma would both cause more expiratory dyspnea. Sinusitis may cause nasal discharge but is not likely to cause the signs this horse is showing. |
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Term
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Definition
| This image shows a horse with skin sloughing due to cutaneous photosensitization. St. John's wort acts as a primary photosensitizer and can lead to photophobia, conjunctivitis, sloughed skin, and icterus. Blue-green algae cause sudden death. Slaframine causes hypersalivation and cantharidin causes colic. |
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Definition
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Term
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Definition
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Term
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Definition
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Term
| A 9-month old foal presents with difficulty walking. You immediately note that the foal appears to have a flexural deformity of the right forelimb consisting of an increased dorsal hoof wall angle of 80 degrees such that the heel does not contact the ground. The coronary band is prominent. You take radiographs which confirm a broken forward hoof-pastern angle. What is the most appropriate treatment for this type of flexural limb deformity? |
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Definition
This case describes a severe flexural deformity of the distal interphalangeal joint, also known as "clubfoot". This is typically a congenital condition in young horses although it can be acquired. A genetic component is suspected. Mild cases can sometimes be managed conservatively with NSAIDs, farriery, exercise and nutritional changes. Severe cases often require surgery; the surgical procedure of choice is desmotomy of the accessory ligament of the deep digital flexor tendon (also known as inferior check ligament desmotomy). The accessory ligament of the deep digital flexor tendon (inferior check ligament) runs from the palmar surface of the proximal metacarpus to the deep flexor tendon in the mid-metacarpal region.
The superior check ligament originates above the knee and attaches to the superficial flexor tendon, and its primary purpose is to support the tendon. Superior check ligament surgery is used to treat a bowed tendon.
Lateral digital extensor tenectomy is a procedure used to treat stringhalt. Transection of the insertion of the semitendinosus is used to treat fibrotic myopathy. |
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Term
| Many times, horses require additional muscle relaxation during anesthesia. Which of the following is commonly used for its property of being a centrally acting muscle relaxant? |
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Definition
| The correct answer is guaifenesin. Unfortunately, the exact mechanism is unknown; however, we do know that guaifenesin acts centrally by blocking nerve impulse transmission at the internuncial neuron level in the subcortical brain, brain stem, and spinal cord. Veterinarians should be careful not to give too much guaifenesin because early signs of toxicity are in the form of increased rigidity. So what does the vet do? Give more guaifenesin, causing respiratory and cardiac arrest. Ketamine is a dissociative agent and is known for its ability to cause hypertonia. Atracurium is a non-depolarizing neuromuscular blocking agent that acts by competitively binding to cholinergic receptors at the motor endplate. Succinylcholine is a depolarizing neuromuscular blocking agent. |
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Term
| Consumption of an ionophore in a horse classically results in ________. |
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Definition
| The correct answer is myocardial toxicity. Although the clinical signs associated with ionophore toxicity are wide, the main postmortem finding is myocardial necrosis. Ionophore toxicity usually occurs accidentally when livestock feeds containing ionophores get mixed up with that of a horse. The main ionophore that results in toxicity is monensin. Horses are very susceptible to monensin toxicity. |
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Term
A horse with peripheral vestibular disease will not have this clinical sign.
a) Left sided head tilt
b) Nystagmus
c) Facial nerve paralysis
d) Conscious proprioceptive deficits of the pelvic limbs |
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Definition
| The correct answer is conscious proprioceptive deficits of the pelvic limbs. Usually the CP deficits will be on the side of the lesion. So you can expect to see right-sided CP deficits on a right-sided central vestibular lesion. Head tilt, facial nerve paralysis, and nystagmus are non-specific signs of vestibular disease. However, they do help you determine on which side the lesion is located. Quick note: if there are multiple cranial nerves paralyzed then you should start thinking this could be central. A right sided head tilt, right sided nerve paralysis, and nystagmus with the fast phase to the left will indicate a right-sided lesion. Abnormal mentation or seizures along with other vestibular disease signs would imply central vestibular disease. |
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Term
| You are examining a 2-year old pony with lameness that worsens after activity or work. The pony displays mild lameness on your exam and is sensitive to deep palpation of the third metacarpal bone of the left front limb. Radiographs reveal periostitis and new bone formation along the second metacarpal bone. No fracture is present. What term describes this condition? |
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Definition
Explanation - This is a description of splints or metacarpal exostosis which involves periostitis of the interosseous ligament between the third and second metacarpal (or metatarsal) bone. Treatment usually involves rest and anti-inflammatory medications, although if the bony exostoses impinge on the suspensory ligament, surgical removal of the proliferative tissue may be indicated.
Sidebone refers to ossification of the alar cartilage of the coffin bone. High ringbone refers to osteoarthritis of the proximal
interphalangeal (pastern) joint. Osselets are inflammation of the periosteum on the dorsal distal epiphyseal surface of the third metacarpal bone and fetlock joint. Thoroughpin is the term for effusion of the tarsal sheath (sheath of the deep digital flexor). |
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Term
| Two mares are presented for crusting dermal lesions on their dorsum and pasterns. The lesions are "paintbrush" like lesions and have purulent material exudating from them. A direct smear of the lesion shows branching, filamentous, gram positive bacteria. What is your most likely diagnosis |
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Definition
| The answer is dermatophilosis. Dermatophilus congolensis is a gram positive, non-acid fast, facultative anaerobic actinomycete. It causes a crusting dermatitis in large animals when there is high moisture on the skin as well as mechanical irritation. Horses with long, wet haircoats are often affected. Lesions are commonly on the dorsum and pasterns of horses and are classically described as paintbrush lesions. It can be diagnosed with a direct smear preparation. Treatment includes keeping the haircoat clean and dry and penicillins if the lesions are severe. Lesions typically heal rapidly. |
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Term
In the Spring of 2001, a syndrome later termed Mare Reproductive Loss Syndrome, also known as MRLS, occurred in central Kentucky. This resulted in the abortion of 20-30% pregnant mares. Which of the following was NOT a manifestation of MRLS?
a) late term abortion
b) early fetal loss
c) fetal or neonatal hemoabdomen
d) neonatal foal deaths
e) fibrinous pericarditis |
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Definition
| The correct answer is fetal or neonatal hemoabdomen. All other choices listed were potential disease manifestations of MRLS. The exact pathogenesis of MRLS is still unknown, but the presence of eastern tent caterpillars was strongly associated with the disease. Later, experimental studies in which pregnant mares were exposed to or fed, via NG tube, eastern tent caterpillars resulted in early and late fetal loss. |
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Term
| You are presented with a 7-year old Morgan horse with the complaint of lameness. You find a normal TPR, but the animal is grossly obese and has evidence of chronic laminitis. The physical exam is otherwise unremarkable. Which of the following best describes this condition? |
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Definition
| EMS is characterized by gross or severe regional obesity and clinical or subclinical laminitis. These animals are insulin-resistant and often have higher than normal insulin levels in blood. |
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Term
You suspect that an 18 year old Quarter Horse mare has recurrent airway obstruction (RAO; also known as chronic obstructive pulmonary disease) based on clinical signs of increased respiratory rate and effort, expiratory wheezes on auscultation, and the age of the horse. What cytologic finding of bronchoalveolar lavage (BAL) fluid would be supportive of RAO?
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Definition
| In health, BAL fluid primarily consists of macrophages. However, in RAO, neutrophils are the predominant cellular finding. RAO typically affects older horses and is a response to environmental allergens. The classic case is the horse that is stalled in the winter and possibly housed in the vicinity of the hay storage. When the horse is exposed to hay allergens (via inhalation), bronchoconstriction and neutrophilic inflammation occur resulting in clinical signs. |
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Term
| You perform a physical exam on a horse and note pale mucous membranes. A CBC is submitted for analysis. What would you expect to see on your CBC if this horse has hemolytic anemia that has been going on for 10 days or more? |
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Definition
Normocytic normochromic anemia
In the horse, it is very uncommon to see morphologic changes to red blood cells, even if there is a strong regenerative response. Therefore, most types of anemia in the horse will be normocytic, normochromic. |
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Term
Which of the following medications is an FDA-approved treatment for equine protozoal myeloencephalitis (EPM)?
a) Ponazuril
b) Trimethoprin sulfa
c) Toltrazuril
d) Pyrimethamine |
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Definition
Ponazuril (trade name: Marquis) is an FDA-approved drug for the treatment of EPM. Ponazuril is an anticoccidial compound with cidal activity against Sarcocystis neurona. Historically, trimethoprim sulfa in COMBINATION with pyrimethamine has been used to treat EPM but is not specifically approved for this use.
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Term
| You have been treating a horse with aminoglycosides and are worried about toxicity as a result of the owner overdosing the horse. Which of the following diagnostic test will be the most practical to perform? |
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Definition
| The correct answer is BUN and creatinine. Toxicity associated with aminoglycoside administration will result in renal tubular nephrosis. Therefore, monitoring changes in BUN and creatinine will be indicated. |
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Term
Consumption of yellow star thistle results in this lesion
a) Destruction of the pons
b) Leukoencephalomalacia of the reticular system
c) Nigropallidal encephalomalacia
d) Destruction of the lateral and medial geniculate nucleus |
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Definition
| The correct answer is nigropallidal encephalomalacia. Consumption of yellow star thistle destroys the globus pallidus and the substantia nigra. These lesions will result in a characteristic dysphagia. |
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Term
| A 3-year old mare is presented for multifocal, round, crusty lesions on her ventral abdomen, which are not particularly pruritic. The owner complains of an increased number of flies around the mare as well as the nearby cattle. What is the most likely diagnosis? |
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Definition
| The correct answer is Haematobia irritans. This fly is commonly known as the horn fly. It causes ventral midline dermatitis, as described in the question, on horses housed near cattle. They are often found around the horns, back, and sides of cattle on cooler days, and will affect the ventral abdomen on hot sunny days. Horn flies feed on blood and cause great economic losses in cattle. It can also serve as an intermediate host to Stephanofilaria stilesi, a filarial parasite that causes plaque lesions on the ventrum of cattle. Treatment and control of the flies is relatively easy with insecticide sprays, dust bags, or insecticide feed additives. Sarcoptes scabei infections and Culicoides hypersensitivity are extremely pruritic. Dermatophytosis is a good differential also, but Haematobia is a better choice, since the horses are affected by flies and are housed near cattle. |
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Term
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Definition
This is an image of a Parascaris equorum egg. It is almost spherical in shape with a brown color and contains a single-celled zygote.
In foals, a significant ascarid burden with Parascaris equorum can lead to intestinal impaction and associated colic. Thrombosis of the mesenteric artery occurs with Strongylus vulgaris infestations. Immune mediated hypersensitivities may occur in adult horses with Parascaris equorum infestations but is unlikely to be a significant cause of the morbidity seen in foals. Larval migration can occur with Parascaris equorum but typically will affect the lungs or liver and this stage of the parasite does not lead to colic. Enteroliths are not caused by gastrointestinal parasitism. |
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Term
Which of these tests would be the best indicator of moldy sweet clover toxicity in a horse?
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Definition
| The correct answer is prothrombin time (PT). Sweet clover can contain a number of fungi that create dicumarol, a warfarin-like toxin. It inhibits vitamin K and interferes with synthesis of factors II, VII, IX, and X. Because factor VII has the shortest half-life of these factors, it will be depleted first. Factor VII is involved in the extrinsic coagulation pathway and would therefore, be elevated first after ingestion of sweet clover. PT is a measure of the extrinsic pathway (and common). PTT is a measure of the intrinsic pathway (and common). TT is a measure of the final steps of coagulation taking fibrinogen to fibrin. Cattle are actually affected by moldy sweet clover toxicity more frequently than horses. |
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Term
| Duodenitis-proximal jejunitis |
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Definition
| Duodenitis-proximal jejunitis, also known as either anterior enteritis, or proximal enteritis best fits this case because of the characteristic reflux, fever, peritoneal fluid characteristics, rectal findings, the depression and relatively less pain than would be expected with an obstruction. The cause is still uncertain, but a relationship of this disease to positive cultures of reflux for Clostridium difficile has been found. Typically these cases are treated medically, which would include repeated decompression of the stomach, IV fluids, replacement of electrolyte deficiencies, analgesics and correction of any acid-base abnormalities. |
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Term
| You are examining a well-muscled 3-year old Quarter Horse stallion for muscle stiffness, difficulty walking, and prolapse of the third eyelid, followed by recumbency. The trainer informed you that the stallion has demonstrated similar clinical signs of lesser severity in the past. Based on this information, you suspect inherited disorder. What is the most appropriate therapy for this acute episode? |
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Definition
| The hereditary disease you should suspect is hyperkalemic periodic paralysis. In acute episodes of HYPP, the clinician should try and drive down the serum potassium. This can be accomplished by administering potassium-free IV fluids (such as 0.9% NaCl) and medications (such as dextrose) to drive potassium into the cell. While LRS could be used when no other IV fluid is available, it does contain potassium. Additionally, enalapril is an ACE inhibitor used for hypertension. One would clearly want to avoid IV solutions that contain high concentrations of potassium (KCl) or are extremely hypertonic (50% dextrose). Finally, while furosemide may sometimes be used to induce diuresis in some cases of HYPP, spironolactone is a potassium-sparring diuretic that would not decrease the serum potassium concentration. |
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Term
Which of these conditions can occur secondary to a streptococcus equi ssp. equi infection?
a) Guttoral pouch empyema
b) Guttoral pouch mycosis
c) GP tympany
d) Ethmoid hematoma |
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Definition
| The correct answer is guttural pouch empyema. With this condition, there is purulent material in the guttural pouch. It can occur from an infection through the pharynx, from a chronic respiratory infection, or via lymphatics, as is the case with streptococcus equi ssp. equi infection. Clinical signs include chronic nasal discharge, dysphagia, and leukocytosis. Guttural pouch tympany is an idiopathic condition of foals where a guttural pouch swells with air. An ethmoid hematoma is a non-neoplastic mass. Guttural pouch mycosis is a fungal infection. |
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Term
| You diagnose this 15-year old mare in the picture with a mild, acute laminitis. Which of the following can be used as treatment for this horse? |
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Definition
| The correct answer is phenoxybenzamine. Phenoxybenzamine is an alpha-adrenergic antagonist promoting vasodilation and restoration of blood flow to the digits. Prednisone is contraindicated in laminitis because corticosteroids are believed to induce the condition. Antibiotics are not indicated unless a secondary bacterial infection develops. Application of a horse shoe would not help and would be very painful in an already sensitive and painful condition. Other medications used to restore blood flow to the digits include acepromazine, isoxsuprine hydrochloride, dimethylsulfoxide (DMSO), heparin, and nitroglycerine. |
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Term
| One of your clients recently purchased a horse that she plans to add to her stable. She is concerned about potential exposure of the horse to Streptococcus equi subsp. equi. Which of the following is the most sensitive test for detecting carriers of the disease? |
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Definition
Testing for Streptococcus equi subsp. equi can be complex. The 3 major tests are PCR, serology, and culture. PCR and serology both detect SeM which is an important virulence factor for the bacteria. Culture is best performed on Columbia CNA agar with 5% sheep or horse blood.
While there are pros and cons to each test, the key to answering this question correctly is focusing on the issues of sensitivity and detecting carriers.
PCR is approximately 3 times more sensitive than culture. In general, sampling the guttural pouch is a better way to detect carriers than the nasopharynx because it is where most carriers harbor the organism.
Serology is the best test for assessing exposure but is not a good tool for detecting carriers. This is because antibodies may be elevated after an infection has been cleared or even after vaccination. It may also be falsely negative if an exposure was recent.
To summarize the best uses of culture, PCR and serology:
Culture is the gold standard for diagnosing a horse with an infection.
PCR is best for detecting asymptomatic carriers, establishing infection status prior to or following transport, and to determine the success of elimination of S. equi from the guttural pouch. PCR cannot distinguish live DNA from dead DNA and may have false positives after a cleared infection. Using PCR in combination with culture may be helpful in such an instance.
Serology is best for determining exposure and the need for vaccination as well as for supporting diagnoses of S equi associated purpura hemorrhagica or of bastard strangles. |
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| Horses living in a sandy region such as California and Florida tend to be predisposed to developing sand enteropathies. If one is suspected, which of the following treatments will be most effective? |
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Definition
| The correct answer is psyllium. Psyllium is a hemicellulose laxative that has the ability to bind with sand and help remove it from the gastrointestinal tract. Feeding the horse in a stall and/or utilizing hay racks will also help the inadvertent consumption of sand that may be ingested if a horse is eating on sandy ground. None of the other answer choices are as effective as psyllium. |
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| Carpal fractures in horses occur most commonly in which carpal bones? |
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Definition
| The correct answer is radial and 3rd carpal bones. Most carpal fractures in horses occur at the dorsal aspect of the carpal joint, particularly at the radial and 3rd carpal bones. Both chip and slab fractures may occur. These fractures usually result in immediate swelling and severe lameness. Diagnosis is based on radiographs and arthroscopic surgical repair is frequently the treatment of choice. |
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| A horse is referred to your practice for further evaluation and treatment of glomerulonephritis. Which of the following is not a treatment option? |
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Definition
| The correct answer is long term furosemide administration. Horses with glomerulonephritis are usually polyuric. Furosemide is only indicated for oliguric renal failure. The other choices are commonly used in the treatment and management of glomerulonephritis. A low protein diet will help decrease the amount of proteinuria and blood urea nitrogen circulating at any given time, therefore helping reduce the degree of azotemia. |
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| Failure of closure of the foramen ovale within the first 48 hours of life in a healthy foal will result in |
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Definition
| The correct answer is shunting of blood from the right atrium to the left atrium. The foramen ovale is a small slit that allows shunting between the right atrium and left atrium in the fetus. Once the foal is born, the lungs expand (right atrial pressure decreases) and the left atrium becomes a higher pressure system than the right. This higher pressure in the left atrium at birth forces the closure of the foramen ovale flap against the septum secundum and, in health, typically fusion of these tissues occurs to permanently close the foramen ovale. However, if the foramen ovale flap does not fuse, this leads to patency. In this case, the flap acts somewhat akin to a one-way valve so when the LA pressure is higher the flap is closed, but when the RA pressure is higher, blood can flow right to left. This occurrence (RA pressure > LA pressure) may happen when the patient coughs, takes a deep breath or sneezes which increases the return of venous blood to the RA. |
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| In the horse, what is the most important muscle or muscle group required for the inspiratory phase of the respiratory cycle? |
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Definition
The correct answer is the diaphragm. Contraction of the diaphragm pushes the abdominal contents back, increasing the length of the thoracic cavity, and pulls the ribs abaxially. The external intercostal muscles assist in pulling the ribs abaxially. This ends up producing subatmospheric intrathoracic pressures and allows inspiration to occur. Contraction of the internal intercostal muscles and the muscles of the abdominal wall decrease lung volume and compress the chest wall. The diaphragm is important in this process because diseases altering innervation or strength of the diaphragm (such as botulism or phrenic nerve damage) or diseases preventing expansion of the diaphragm into the abdomen (such as large colon torsion) are important causes of respiratory distress and potentially hypoxemia and death.
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Term
| Treatment for Cyantide toxicity |
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Definition
| The bright red-colored blood and mucous membranes with signs of respiratory distress are typical findings for cyanide toxicity. There are many plants that can accumulate cyanide to levels that are toxic to horses. Treatment is with sodium nitrate or sodium thiosulfate IV |
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Definition
| The correct answer is 9 years. This is useful for the purposes of aging horses. It is a longitudinal groove noted on I3. I1 erupts at 2.5 years, I2 erupts at 3.5 years, and I3 at 4.5 years. The canine tooth erupts at 5 years. The cup from I1 disappears at 6 years, I2 at 7 years, and I3 at 8 years. Galvayne's groove is half way down the tooth at 15 years and then completely down at 20 years of age. |
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Term
| Mast cell tumours in horses |
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Definition
| Mast cell tumors in horses are benign. They can occur anywhere on the horse, but are often found in the dermis or subcutis of the head or legs. The tumors may also invade underlying musculature, but are often walled off by aggregates of fibrous stroma. |
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Definition
| This is in contrast to Ehrlichia risticii (which was recently renamed Neorickettsia risticii), the agent of Potomac horse fever, which survives in monocytes and is rarely found in a blood smear |
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| Which of these viruses are normally found in the upper respiratory tract of the horse? |
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Definition
| The correct answer is equine adenovirus. Adenovirus is normal in the upper respiratory tract but can cause a lower respiratory tract infection in immunocompromised individuals, particularly foals with failure of passive transfer or combined immunodeficiency. In fact, adenovirus is the most common cause of death in foals with those two conditions, leading to an often fatal pneumonia. |
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| What diagnostic technique would be most useful for diagnosing a Dictyocaulus arnfeldi infection in a donkey? |
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Definition
| The correct answer is Baermann. Dictyocaulus is the lungworm of horses/donkeys. The life cycle of the worm is that an infective larva is ingested and migrates through the mesenteric lymph nodes through lymphatics to the lung where it develops into an adult, producing eggs that are coughed up, swallowed, and passed in the feces. 1st stage larvae hatch in the feces and are most likely to be detected with a Baermann. Other useful diagnostic techniques include a transtracheal wash, which may show eosinophils and possibly parasites, ova, or larvae. It is rare for horses to have patent infections. You will observe them more often in foals than in adult horses. Donkeys are considered the reservoir. |
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Definition
| colitis is associated with metabolic acidemia, acute kidney injury is associated with hyperkalemia, and equine Cushing's syndrome is associated with hyperglycemia. |
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| What is the daily normal water consumption rate for an average 450 kg horse? |
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Definition
| The correct answer is 30 liters of water. Horses consume about 50-70 ml water/kg/day, this will vary somewhat based on temperature, diet, and other factors. However, of these choices, 30 liters is the best choice. Normal urine production in the horse is about 15-30 ml/kg/day |
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| Measurement of blood lactate is commonly used in foals and adult horses as an overall reflection of cardiovascular status. What is the normal blood lactate in a healthy foal or horse? |
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Definition
The correct answer is less than 2.5 mmol/L. It is important to remember a general reference range for all diagnostic laboratory data; lactate is commonly performed on hand-held lactometers that do not provide a reference range.
As you may recall, lactate is produced from pyruvate in anaerobic environments to keep the process of glycolysis running. When a horse/foal is hypovolemic, blood lactate may increase because of poor blood perfusion to the body. Several studies have investigated blood and peritoneal lactate as a means of predicting survival in neonatal sepsis and equine colic. It may be necessary to look up these studies if you want exact findings (different reports provide different findings), but not surprisingly, the higher the lactate, the poorer the prognosis. |
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| For neonatal isoerythrolysis to occur, which of these pairs must mate? |
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Definition
| The correct answer is stallion positive for Qa and mare negative for Qa. For neonatal isoerythrolysis to occur, the mare must develop antibodies to the foal's red blood cell antigens. Aa and Qa are the two antigens most frequently implicated in this condition. For this condition to occur, the foal must inherit the Aa or Qa antigen from the stallion, and the mare must be negative for the antigen (if she was positive, meaning she has the Qa antigen on her RBCs, she would not make antibodies against it). Then, when the mare becomes exposed to the foal's red blood cell antigens, she makes antibodies. When she passes these antibodies to the foal through colostrum, an acute hemolytic event will occur in the foal. In most cases, the first time a mare has a foal with the antigen, she will not produce sufficient antibodies to cause severe damage to the foal. Therefore, this condition is usually seen in multiparous dams or in mares that have previously had a blood transfusion that exposed them to the red blood cell antigens. |
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Definition
| The correct answer is Pseudomonas. Pseudomonas is the most common agent causing bacterial keratitis in the horse. The gram negative cytology provides further evidence that it is the likely culprit. Staphylococcus can cause keratitis in horses but is gram positive. E. coli and Pasteurella are not agents that are commonly involved with keratitis in the horse. |
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There are a number of drugs that are used extra label in beef cattle. When working with any food animal, you always have to consider milk and meat withdrawal. What is the meat withdrawal (in days) for xylazine, tolazoline, lidocaine, and meloxicam, respectively?
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Definition
The correct answer is 4, 8, 4, and 15. Remember that xylazine is extremely potent in cattle, taking 10% of the dose that would be given to a horse of equivalent size is sufficient .
Tolazoline is an alpha 2 antagonist. Give the same volume as xylazine. Lidocaine is commonly used during c-sections in cattle. If a producer is doing a c-section as a salvage procedure, it is important to inform that person that the cow cannot go to slaughter for 4 days.
www. Farad is the site to search for information of this type.
Meloxicam is being used more and more. It is longer acting (~ 4 days) than banamine, but banamine only has 4 days of meat withdrawal. If you plan on going into production medicine, it is important to memorize the numbers for these commonly used drugs so that you can inform the producer. |
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| A cow presents due to a decrease in milk production. On physical exam, you were unable to hear the heart clearly (it is muffled). You decide to perform an ECG and immediately recognize that this cow has electrical alternans. What is most likely to be occurring? |
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Definition
| The correct answer is pericardial effusion. Electrical alternans is a classic finding in cases where there is pericardial effusion. Electrical alternans is characterized by different amplitudes of multiple successive R waves in the QRS complex. This is thought to be a result of the heart shifting around within the fluid filled compartment of the pericardial sac. |
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