Exposure to an infected animal or fomite followed by exposure of the skin to a critical load of infective spores (arthrospores), increased moisture on the skin surface to facilitate sporulation and microtrauma. 

Group housing of animals (pet store, shelter, cattery)

Persians, Yorkies and Jack Russel Terriers 

*Persians and Yorkies may develop subcutaneous nodules*

Working and hunting dogs may develop kerion lesions more commonly

Focal or multifocal to widespread hair loss, scaling, crusting and erythema are most common

Lesions tend to be asymmetric and can affect any body location but the face, ears and distal extremities are most common

Pruritus is variable 

Infected hairs are wider and paler in appearance, they may appear frayed or fuzzy in outline in the clear definition between cuticle cortex and medulla is lost

Ectothrix spores cuffing the hair may be present 

91%-100% of patients with untreated spontaneous infection will show positive fluorescence

Use a lamp with a wavelength of 320-400 nm and magnification, hold 2-4 cm from the animals hair, start at the head and be systematic, look for apple-green florescence   

#1 Confinement - confinement of a patient to a limited area will ease cleaning and limit spread, owners should avoid skin-to-skin contact, wear gloves, use soap and water for hand washing and wash clothing after socializing with the animal 

#2 Cleaning (most homes can be decontaminated with 1-2 cleanings after cure) - twice weekly, will help to reduce false positive test results, wash all items the pet comes in contact with twice with a long cycle and , remove visible debris and then use an over the counter bathroom disinfectant or product with accelerated H₂0₂ to clean surfaces, steam cleaning once will decontaminate carpets

Lime sulfur - twice weekly, 1:16 dilution (high []'s may be irritating to the skin), avoid contact with fabrics or jewelry, good residual activity  

Miconazole 2%/chlorhexadine gluconate 2% - 3 minutes of contact time is sporicidal, can be use on exposed but uninfected animals as well, no residual activity. Shampoo or mousse products may be useful. 

Enilconazole - 1:50 or 1:100 dilution, use in cats 

rinses or dips should be repeated every 5 to 7 days.

other agents with topical efficacy include zinc pyrithionine, selenium sulfide, ketoconazole and hydroxychavicol. 

Other notes: monistat 2% miconazole vaginal cream can be used around the eyes safely 

Itraconazole - never use a compounded product!, in cats use 5mg/kg PO SID week on/week off, may cause non-significant elevations in liver enzymes (ALT), in small dogs use 5mg/kg PO SID until cure 

Terbinafine - 30-40 mg/kg PO SID until cure, GI side effects may occur in cats

Griseofulvin is no longer recommended due to safer alternatives and ketoconazole/fluconazole do not have residual activity and have a higher MIC compared to terbinafine so are also not recommended 

Clinical cure will occur before mycological cure

Generally 2 negative cultures taken at a weekly interval is sufficient but in a healthy animal that is woods lamp negative 1 negative culture may suffice. 

• With dermatophytes, the medium will change color to red as soon as a white/buff-colored fluffy colony becomes visible on the medium
• Fungal growth may occur in 5-7 days, but it may take up to 3 weeks. Therefore, wait 3 weeks before declaring a fungal culture negative

Need to do a stained slide prep to examine all suspect colonies

• Pick up surface of colony with clear acetate tape
• Spread on glass slide flooded with lactophenol cotton blue/new methylene blue
• Add more of same stain and coverslip
• Examine for presence of macroconidia

What is the asexual state of a fungi called?

What is the sexual state of a fungi called?

Asexual = anamorph

sexual = teleomorph 

The cell walls are composed primarily of beta-1,3-glucan polymers and cellulose with very little chitin, mycolaminarin is used for energy storage, The vegetative state is deployed and there is a complex lifecycle with both asexual and sexual reproduction.

DTM is essentially a Sabouraud’s dextrose agar containing cyclohexamide, gentamicin and chlortetracycline with phenol red as a PH indicator. 

dermatophytes first used pro Tien in the medium, producing alkaline metabolites that turn the medium from yellow to red. 

1 to 2 drops of injectable vitamin B complex because trichophyton equinum var equinum has a niacin requirement for growth.

* trichophyton verrucosum requires thiamine, with some strains requiring inositol for growth.*

Malassezia infection in cattle often presents as an otitis externa.

M. sympodialis may occur in the summer and M. globosa may occur in the winter.

A subcutaneous and systemic disease associated with pigmented fungal elements. 

2 forms: phaeohyphomycosis (separate hyphae and yeast) and chromoblastomycosis (large rounded dark walled cells). 

Dog - Disease is usually associated with puncture wounds caused by thorns or splinters or wounds contaminated by soil.

Cat - most common and intact male free roaming cats, likely acquired through contaminated clause or teeth during fights.

*In horses, can be associated with previous wound sites and may develop as a firm nodular swelling that progresses to lymphangitis and may ulcerate.*

The traditional treatment is a PO supersaturated solution of potassium iodide. Continue treatment for four weeks beyond clinical cure. Watch for signs of toxicity (iodism - ocular nasal discharge, dry hair coat, scaly skin) and it’s observed stop for one week then re-institute at a lower dosage.

Ketoconazole, itraconazole (treatment of choice in cats) or terbinifine (dogs) may also be successful. 

An oomycete, Pythium insidiosum - produces a motile flagellate zoospore with a cell wall containing cellulose and beta glucan without chitin and little ergosterol.

 
Zoospores lose their flagella to become encysted in tissue, then develop a germ tube which facilitates penetration an invasion by hyphal elements. 

BAD1 and WI-1

These antigens function in the adherence of the yeast to host cells and act as immune modulators to suppress the inflammatory response. 

A young intact large or sporting breed dog.

Dogs have a 10x increased risk of infection compared to humans.

Itraconazole or fluconazole for 60 days and 4 weeks beyond resolution. 

Coccidioides, a dimorphic saprophytic soil fungus found in sandy alkaline soil‘s in areas with a high environmental temperature low rainfall and low elevation. can be isolated from rodent boroughs in desert like areas.

rainfall or other disturbances can release arthroconidia which are then wind dispersed. 

Dogs - Boxers and Doberman pinchers

The disease is rare and cats.

The current drugs of choice are the azole antifungals: ketoconazole, itraconazole, fluconazole.

Animals with disseminated disease should be treated for a minimum of one year and for 3 to 6 months after remission of clinical signs

Cryptococcus neoformans var neoformans can be isolated from trees fruit and soil contaminated with bird droppings, especially pigeons.

Cryptococcus neoformans var gattii Is associated with environments with trees, particularly eucalyptus.

Cryptococcus! Young adults have the highest risk. 40% of cats will have skin lesions presenting as papules nodules abscesses ulcers and draining tracts.

It can also cause disease in a variety of other animals. 

Amphotericin B is the most effective agent. Used in combination with flucytosine for cats with CNS disease. 

For less severely affected animals the apple anti-fungal drugs can be used. Itraconazole may be the best bet for a mildly affected cat. 

Histoplasma capsulatum, a dimorphic saprophytic soil fungus associated with warm moist humid conditions and soil containing nitrogen rich organic matter such as bird and bat excrement or decaying wood.

most cases occur in the central United States (Mississippi river valley). 

A young dog - Weimaraner and Brittany spaniels may be predisposed.

Histoplasma is rare in cats.

Itraconazole! For severe cases combine with amphotericin B. Fluconazole and ketoconazole are not recommended.

All animals with clinical histoplasmosis should be treated because of the potential for dissemination of the organisms.

-Malassezia may act as a continuous allergic stimulus

-Cellular and humoral immune response leads to increased sensitization

-Cellular response is mainly Th2 type with an increased IL-4 and IL-5 production compared to healthy controls

-Cytokine environment that is dominated by IL-12 would favour Th1 cell development, whereas IL-4 and IL-13 would stimulate the development of Th2 cells

-T helper cells would activate B lymphocytes and stimulate them to differentiate into antibody-forming plasma cells. By secreting IL-2 and IFN-gamma, Th1 cells would promote IgG production

-IL-4 and IL-13 from Th2 cells would promote immunoglobulin class switching to IgE

-Production of Malassezia specific IgG antibodies could potentially provide a degree of protective immunity against Malassezia organisms

-The development of allergen specific IgE antibodies could lead to sensitization of cutaneous mast cells. Subsequent exposure to Malassezia allergens could trigger the release of inflammatory mediators and result in Type 1 hypersensitivity reaction

-Trees, fruits, and soil contaminated with bird feces 

-Guano: alkaline, hyperosmolar environment rich in nitrogen 

-remains viable for 2 years

-Cryptococcus neoformans and C.gatti

-Also infects humans, dogs, ferrets, horses, goats, sheep, cattle, and koalas

-Haploid, budding yeast--> filamentous form

-"Perfect state"

-Genus contains 39 variants

-C.bacillisporus- emerging, humans

-Five serotypes= A, B, C, D, AD

-Antigenic differences of serotypes in the capsule

-Size of the inoculum, the virulence of the cryptococcal strain, and the status of host defenses

-Polysaccharide capsule, melanin, mannitol, laccase, and other enzymes ("a sugar-coated killer with designer genes")

-Glucoronoxylomannan (GXM)

-Once the organism is inhaled, the capsule enlarges and inhibits phagocytosis through its negative charge and via blockage of the Fc portion of antibodies

-Depletes complement and inhibits T cells

-Inappetence, weight loss, fever

-Respiratory signs

-GI signs- large bowel diarrhea with tenesmus, mucous and frank blood

-Cutaneous involvement is very uncommon

-Pointers, Weimaraners, Brittany Spaniels, working dogs

1) Localized or fixed cutaneous form (firm multifocal nodules and ulcerated plaques, seen in cats with non-healing fight wound abscess

2) Cutaneous-lymphatic form (skin SQ tissues and "cording" of the lymphatics, more common in horses and humans

3) Disseminated or systemic form (uncommon sequel to cutaneous-lymphatic form; liver and lungs primary site, more common in cats; symptoms may be vague)

-Ubiquitous saprophytes

-Tropical/subtropical

-Normal flora

-Port of entry (GI tract, respiratory tract, insect bites, and wounds)

-2 main orders: 

1) Entomophthorales (Basidiobolus, Conidiobolus- Chronic and localized---> affects IMMMUNOCOMPETENT

2) Mucorales (Rhizopus, Absidia, Mucor, Sakenaea- Acute infections and progressive---> affects IMMUNOCOMPROMISED

-Presence of a wide eosinophilic sleeve surrounding the hyphae- "Splendore-Hoeppli" 

-With pythiosis/lagenidiosis, this sleeve is usually thin to absent

-Biflagellate aquatic zoospore which is released into warm water environments

-encysts in damaged skin or the GI mucosa

1) Fatal dermatologic and disseminated disease in dogs in SE USA (pyogranulomatous vasculitis and infection of great vessels)

2) Chronic ulcerative nodular dermatopathy

***parasites that infect algae, fungi, rotifers, nematodes, crustaceans and insects

-BAD1= WI-1: function in the adherence of the yeast to host cells, immune modulators to suppress inflammatory process (TNF-alpha)

-Infection via inhalation of spores from mycelial growth in the environment

-Hematogenous spread to skin, eyes, bones, LN, SQ tissues, external nares, brain, and testes

-Cough, dyspnea, fever, anorexia, weight loss, lameness, skin disease, ocular disease, non-specific clinical signs

-Skin lesions usually over areas of infected bone

-Young, male dogs (esp. Boxers and Dobermans)

-Travel history---> Valley Fever seen in SE USA

-Historically known as lipophilic, non-lipid dependent yeast

-Utilizes lipid fractions in peptone component of Sabouraud's dextrose agar

-Hydrolases (lipase, phospholipase, aspartyl proteases, acid spinogomyelinases) and biofilm

-Mis-sense mutation in ERG11 gene 

-encodes lanosterol 14-alpha-demethylase

-Drug efflux pump mutation

-Nannizziopsis vriessi

-Colonies are white, cottony, powdery, and quite dense with cream-colored reverse surface

-Morphology and morphometry reveal pyriform to cylindrical, sessile, aleuricondidia on branched, thin-walled hyphae

-Opportunistic fungi (soil saprophytic molds)

-Common contaminant of lab cultures

-Hospitals, nosocomial infection

-Nondematiaceous fungi (non-pigmented)

-eg.Fusarium, Penicillium, Scedosporium, Geotrichum, Paecilomuces, Monocillium indicum, etc

-Form hyphal elements in tissue after inoculation

-Granulomatous disease may lead to hypercalcemia

-Chronic granulomatous fungal disease

-Tissue grains, granules

-Dense colonies of organisms, necrotic debris

-Pigmented fungi with black grains

1) Curvularia species

-Non-pigmented fungi- white grains

 1)Pseuuudallescheria boydii and Scedosporium apiospermum

-Opportunistic infection

-Other Mycetomas (eg Actinomycotic mycetomas, botryomycosis, pseudomycetomas)

1) Zoophilic: Adapted to living on animals

(M.canis, M.equinum, and T.equinum) 

-Sylvatic dermatophytes (T.mentagrophytes, M.persicolor)

2) Anthropophilic: Adapted to humans

3) Geophilic: Adapted to soil saprophytes

-M.gypseum

-Singular or multifocal

-Poorly circumscribed

-Ulcerating or fistulating pigmented nodules and plaques (may be confused with melanoma)

-Fungal pigmentation is seen in tissue

-Cats> dogs

-Face, distal extremities

-Also cerebral and disseminated forms

-Prognosis decreases with extent of disease

-Fontana-Masson: stains melanin- see in hyphae

-Pigmented fungal organisms in small aggregrates

-Direct exam of exudate or macerated tissue mounted in 10% KOH may reveal pigmented fungal elements

-Histopathology reveals PG, granulomatous, or lymphocyte rich granulomatous dermatitis and panniculitis

-Pigmented epitheloid macrophages or multinucleated giant cells

-Culture

-Use Fontana-Masson stain to stain melanin (seen in hyphae)

1) Arthrospores adhere to keratin

2) Conidial germination within 6 hours of contact

3) Invasion of cornified tissues (stratum corneum, hair shafts, claws)

-Cell-mediated

-Epidermal hyperplasia from damaged keratinocytes

-Intracorneal microabscesses from superficial perivascular dermatitis and exocytosis

-Mural and luminal folliculitis---> Furunculosis

1) Glycopeptide- immunologically active portion of cell wall

-Carbohydrate portion- immediate-type hypersensitivity

-Peptide portion- delayed-type hypersensitivity

2) Secreted keratinases

1) Temperature

2) Oxidation-reduction potential

• It has no chitin and little ergosterol
• Caspofungin is the main drug used in the treatment of Pythium because it blocks the synthesis of Beta (1,3)-D-glucan of the fungal cell wall through non-competitive inhibition of the enzyme Beta (1,3)-D-glucan synthase

• The principal virulence factors of C.neoformans are a polysaccharide capsule and melanin production
• It also has the ability to grow at body temperature and the secretion of extracellular enzymes

• Zoophilic- the natural reservoir is a hedgehog
• Colonies are flat, white, powdery with yellow reverse pigment
• Microconidia are slender and clavate, macroconidia are smooth, thin-walled and clavate

• Fungal infection of the hair shaft (extra-follicular)
• Piedraia hortae= black piedra
• Trichosporon beigelii= white piedra
• Diagnose microscopic + fungal culture
• Treatments include shaving to remove infected hairs, topical +/- systemic (terbinafine) antifungals

• Ligands on canine corneocytes
  • Mannosyl-bearing carbohydrates residues
  • glycoproteins on yeast cell walls bind to these

• Chromomycosis (Pigmented fungi)
  • Phaeohyphomycosis (hyphal)
  • Chromoblastomycosis (yeast-like)
• Hyalophymycosis (non-pigmented fungi)

• Oomyctes organism
  • probably aquatic and most common in SE USA
• Skin and SQ lesions involving legs, groin, trunk, tail
• Regional lymphadenopathy
• Spreads to involve large blood vessels-->aneurysm--> rupture and death
• Diagnose via culture, PCR and ELISA
• Early surgical removal of cutaneous lesions may be curative

• Dogs 10x risk compared to humans
• Disease in cats is rare (Siamese may be predisposed)
• Diagnose by finding organism
  • Cytology: 8-15um with thick wall and broad based buds
  • Histopathology
• ELISA (antigen in urine, serum, CSF or BALF)
• Treat: itraconazole, fluconazole, Amphotericin B
• Continue treatment 1 month past resolution

• Endemic areas (eastern USA)
  • Mississippi, Missouri, Ohio River Valleys
  • Nitrogen rich soil (enriched soil chicken, starling or bat excreta)
• Routes of exposure
  • Inhalation---> pulmonary disease
  • Ingestion---> GI disease
  • Rarely direct skin inoculation
  • Most infections asymptomatic
• May have hematogenous and lymphatic dissemination by macrophages containing organisms

• Numerous 1-5um yeasts inside macrophages, narrow based buds 
  • may need to differentiate from Leishmania inside macrophages
• Quantitative antigen enzyme immunoassay (MiraVista Diagnostics), urine BALF
• Antibody tests
• Culture not recommended

• It is an iron binding protein
• shown to inhibit the growth of Malassezia pachydermatis in vitro

• Zymosan- however this is debatable and some have contributed it to contamination in those studies

• Glycopeptide- immunologically active portion of cell wall
  • Carbohydrate portion- immediate type hypersensitivity
  • Peptide portion- delayed type hypersensitivity
• Secreted keratinases

• Innate, antibody and cell mediated responses
• Hypersensitivity reactions
  • cell mediated response lead to delayed type hypersensitivity
• Keratinocytes recognize Malassezia through Toll like receptors
  • Upregulate IL-10 and TGF-β
  • Downregulate IL-1α

• Mannan
• Zymosan

• Langerin (C-type lectin)

• Many species of pigmented fungi isolated from lesions (Alternaria, Bipolaris, Cladophialophora, Cladosporium, Exophiala, Scedosporium and others)
• GSD may be predisposed
• Pigmented hyphae found on cytology or histopathology
• Identify by culture or PCR
• Tx via surgical excision (if possible) or antifungals