Wet conditions/trauma of interdigital skin
 Interdigital dermatitis
 F. necrophorum penetrates stratum corneum
 D. nodosus proteases cause hoof separation and allow the deeper

penetration of F. necrophorum
 With virulent strains, under-running spreads from axial heel, laterally and

anteriorly under sole to abaxial wall and toe 

• D. nodosus only survives for a few days outside the feet of ruminants, up to 7 days in mud.

•   Transmission requires mean daily temperatures 10C or more, and 2 or 3 months exceeding 50mm rainfall/month (Australian data)

•   Virulent strains do not readily cause latent infections

•   Persistent clinical lesions may occur under cool conditions 

•   Mixture of interdigital dermatitis, under-run heels and severe under-run hooves.

•   It is not possible to differentiate clinically between interdigital dermatitis and the

  early stages of footrot, or between benign footrot and early virulent footrot.

•   Mild strains result only in separation at the heels and back of the sole (benign

  footrot), while virulent strains can result in complete separation of the horn of the

  hoof wall and sole.

•   Characteristic smell

•   Chronic cases – misshapen hoof, trapping dirt and inflammatory exudates

•   Advanced footrot - extremely lame, recumbent for long periods, flystrike on foot

  and flanks 

0. is it footrot? How virulent is it?

•   Clinical examination of many individuals (?10-40)

•   May need re-inspection after 2 weeks to assess progression

1.   Main DDX OID, CODD 

Topical treatment
o Gentle paring and application of oxytet spray (small numbers) o Footbathing

 3% formalin, formalin concentrations exceeding 5% can result in foot damage and should be avoided.

 10% zinc sulphate (extended period or frequent)
 Clean feet (esp. formalin) and dry standing afterwards important  Cure rates of up to 80% feet, but not great against advanced

lesions 

Vaccination

o Therapeutic effect – some respond to first injection, 50-100% to second injection.



Parenteral antibiotics i/m
o 85% or more cure rates, effective against advanced lesions o Paring not needed
o Dry conditions required 24hrs post treatment
o Oxytetracycline 20mg/kg or high dose Pen & Strep 

• If prevalence high, treatments as above to reduce number of infected animals.

•   Aim of control is to achieve;

o Low incidence of footrot

o Low % of early lesions developing into severe lesions  Based on footbathing and vaccination

Vaccination

•   Two doses needed for protection

•   Given before transmission period if possible, difficult to predict in UK

•   4-6 months protection in UK breeds

•   Reactions and reduced LW gain – not ideal for fat lambs

•   In many UK flocks, vaccination is targeted at specific high-risk groups of animals,

  such as rams before mating 

  Footbaths

•   To stop development of early interdigital lesions into severe lesions

•   To reduce environmental contamination

•   During transmission periods (?from May if not too dry) – weekly or fortnightly

•   Some protection from re-infection for 24 hours after bathing, and no records of

  sheep becoming infected from pasture after 24hrs rest – therefore move to “clean” pasture (rested two weeks) after treatment probably of minor importance in control (c.f. eradication)

•   Foot paring has no role in preventing footrot 

Resistance to footrot appears is moderately hereditable and breeding of resistant sheep by selective culling could be considered as a potential control strategy. However, while breeding of resistant sheep is a genuine possibility, the value of this strategy is limited by the stratified system of sheep production in the UK. 

Footrot can be eradicated from a farm by de-stocking for 7 days and re-stocking with clean sheep
Eradication from a flock involves intensive effort during a non-transmission phase when all virulent footrot infections should be clinically apparent, and all pastures safe for clean sheep (c.f. control programs, when effort is concentrated in the transmission period). The identification of such periods in the UK is problematic.

•   Prevalence should be 5% or lower

•   All feet examined

•   Cases treated or culled – must be isolated if transmission possible

•   Inspection repeated once or twice

•   Non-responders culled

•   Avoid re-introduction

o Purchase clean replacements – impossible in UK
o Quarantine – extended periods needed to eradicate footrot in the

purchased sheep – often not practical o Closed flock

 Climate change leading to drier summers may make eradication a practical

option over areas of the UK 

(45% of lameness)
Scald is a major cause of lameness in itself; in addition it is also the first stage in the pathogenesis of footrot and septic pedal arthritis.

Aetiology

F. necrophorum infection alone - does not require D. nodosus. It is clinically indistinguishable from benign footrot, caused by F. necrophorum and benign strains of D. nodosus, and early virulent footrot.

Moist conditions and trauma caused by long wet grass is often the predisposing factor, particularly in lambs. Straw bedding may play a similar role in outbreaks in housed ewes. Typically many animals in the flock are lame in one or more foot. In extreme cases, 90% of the flock can be affected 

•   Interdigital skin inflamed and swollen

•   Layer of white necrotic material

•   May progress to erosions of ID skin tissue

•   No under- running of horn, no smell

•   Lameness can persist for several months if untreated 

Individual cases - oxytetracycline sprays 77

 Group
o Move to dry pasture ideal but unlikely
o Management of areas around troughs and gates etc.
o 10% zinc sulphate solution or 3% formalin footbath, followed by dry

standing for 1 hour
o Repeat 5 - 14 day intervals throughout the risk period 

A virulent, rapidly spreading foot disease similar to digital dermatitis in cattle has been described in sheep of all ages. Appeared widespread in early 2000’s. Prevalence seems to have decreases in recent years.
Aetiology

An association has been made between the disease and the presence of motile spirochaetes. However, motile spirochaetes may also be present on the lower limbs of healthy sheep. In some cases proliferative lesions at the coronary band appear similar to orf, but orf virus has not consistently been identified in scab material from the lesions.

Epidemiology

In some areas up to 50% of sheep flocks have been affected 

•   High morbidity rate (up to 70%)

•   Severe lameness

•   Initially, full thickness skin ulceration at the coronary band (c.f. scald and footrot)

•   Hoof wall under-run from coronary band and often shed to expose the sensitive

  laminae which may bleed profusely.

•   1 cm diameter circular areas of hair loss and ulceration sometimes seen on skin

  below the fetlock joints.
  Often cases of virulent footrot/mixed infections in same flock

  
  

  Pathogenesis

  F. necrophorum and D. nodosus often present, and may increase severity. Formalin footbaths may increase the severity 

0. Treatment and Control

•   Lesions heal quickly after topical treatment with oxytetracycline aerosol sprays

•   Response to foot trimming and foot-bathing in formalin or zinc sulphate is poor.

•   Footbathing for 20 minutes in tylosin or lincomycin antibiotic solutions followed by

  dry standing appears to be effective for prevention and treatment of ovine digital dermatitis (for example: Tylan soluble, Elanco, at a rate of 1 g of powder per litre of water).

•   Individual cases may benefit from systemic antibiotic treatment. 

0. FOOT ABSCESS (Septic pedal arthritis) - failure to manage lameness

   TOE GRANULOMA
   TOE ABSCESS (White line abscess) - pairing

   SHELLY TOE

   LAMINITIS
   INTERDIGITAL FIBROMAS