Ruminant foot ID

what causes foot and mouth disease?

Foot and mouth disease virus (an aphthovirus)

what animals are affected by foot and mouth disease?

cloven hoofed animals (cattle, swine, sheep, goats + wild species)

what are clinical signs of FMD?

• fever

• lameness

• lesions on tongue, feet, snout, teats

• high morbidity, low mortality

what is the economic factors to bovine digital dermatitis?

• causes reduction in milk yields and reproduction

• costs of treatment

• increased labour costs

what pathological lesions do we see with bovine digital dermatitis?

ulcerative lesions located above coronet between heel bulbs

• lesions usually seen in housing periods

how do we treat bovine digital dermatitis?

• foot baths

  • chemical - formalin / copper sulphate (more commonly used)

  • antibiotic - Lincospectin (not commonly used)

• topical tetracycline blue spray (no milk withhold)

• penicillin (systemic) or macrolides (systemic/oral) - but not used in dairy cattle due to milk withhold

how is bovine DD transmitted?

• slurry

• direct contact

• foot trimming equipment

what aetiological agents can cause bovine digital dermatitis?

• Spirochaetes (Treponemes)

  • T. medium-like

  • T. phagedenis-like

  • T. pedis

• Fusobacteria

• Dichelobacter

• Campylobacter

• Mycoplasma

what is the appearance of spirochaete on skin biopsies of bovine DD lesions?

stained with silver nitrate - see spiral organisms

what are the virulence factors of treponemes?

• adhesions to host extra-cellular matrix molecules and fibrinogen

• flagellar between inner and outer membrane allowing motility - important for invasion

how do we diagnose bovine DD?

visually (lameness and lesion score)

how can we control bovine DD?

• regular foot baths

• improve farm hygiene

• appropriate foot trimming with disinfected equipment

• biosecurity

what are the economic factors of contagious ovine digital dermatitis?

• lost production

• preventative measures

• treatment

what are similarities and differences between contagious ovine DD and bovine DD?

• similarities

  • similar foot lesions

  • pathology similar - spirochaetes —> same treponeme groups

• differences

  • CODD more severe - frequently results in loss of entire foot horn capsule

  • more substantial pain and suffering due to the lesions in CODD

how do we diagnose contagious ovine DD?

visually (lameness and lesion score)

how do we treat contagious ovine DD?

• foot baths

  • chemical - formalin / zinc sulphate (copper sulphate not used due to copper toxicity in sheep)

  • antibiotic - lincospectin (less commonly used)

• topical tetracycline blue spray

• amoxicillin/penicillin (systemic) or macrolides (systemic/oral) - individual rather than whole flock best option

what are risk factors for CODD?

• dairy cattle in close proximity (risk factor as BDD has same bacteria)

• foot rot is risk factor

• sheep can carry disease onto new farms

how can we control CODD?

• regular foot bathing

• improve farm hygiene

• appropriate foot trimming with disinfected equipment - do not trim infected sheep foot lesions

• individual systemic long acting amoxicillin

• flock biosecurity - purchase from sources with known health status

• isolate lame sheep

what are economical factors for ovine footrot?

• see rapid weight loss in affected animals - production losses

• preventative measures and treatment expensive

what does ovine footrot cause?

• painful lesions - interdigital dermatitis then interdigital hoof wall lesions —> separation of hoof from underlying tissue

• lameness and loss of body condition (due to reduced feed intake)

• can cause death (due to starvation and thirst)

what is the aetiological agent for ovine footrot?

Dichelobacter nodosus (straight/curved rod, not flagellated, fastidious, gram -ve anaerobe)

what are virulence factors for Dichelobacter nodosus?

• produce extracellular proteases

• fimbriae —> motility and adherence

how is ovine footrot transmitted?

• source of infection = infected foot

• direct or indirect contact

• survives short time in environment

• less transmission during dry periods

how do we diagnose ovine footrot?

• diagnose based on clinical signs

• culture-based diagnosis available but not routine as fastidious (similar to CODD and BDD)

how can we treat ovine footrot?

• hoof trimming - possibly helps but recent guidelines advise against

• topical disinfectants

  • formalin

  • zinc sulfate

  • oxytetracycline spray

• foot baths

  • formalin + zinc sulfate

• systemic amoxicillin and streptomycin

how can we control ovine footrot?

• regular foot bathing

• antibiotic injections of long acting amoxicillin

• vaccination

• biosecurity

• isolation of infected animals

• selection for resistance (culling)

what is the link between ovine foot diseases?

can lead to one another -

ovine interdigital dermatitis (scald)

—> foot rot

—> contagious ovine digital dermatitis

when does ovine interdigital dermatitis (scald) occur?

when wet underfoot

what are key differences between scald and ovine foot rot / CODD?

• scald less severe / less painful

• no under-running of hoof wall or sole with scald

  • foot rot - often get separating of horns

  • CODD - often get whole hoof wall drop off

• no foul smell with scald

what pathological lesions do we see with scald?

• red/pink inflammation of skin between claws

• white/grey pasty scum on top

what aetiological agents cause scald?

• Dichelobacter nodosus

• also role of Fusobacterium necrophorum

what are aetiological agents causing bovine foul in the foot / interdigital phlegmon?

Fusobacterium necrophorum considered to be main cause

(gram +ve, anaerobic rods)

what is the key virulence factor of Fusobacterium necrophorum?

leukotoxin = secreted protein that exerts cytotoxic activity on host cells

what is risk factor for bovine foul in the foot?

requires injury to interdigital skin - sudden onset, acute disease

(cf to BDD - usually chronic)

what are clinical signs of foul in the foot?

• severe lameness (worse than BDD due to acute nature)

• animal holds leg in the air to relieve pressure

• swelling of interdigital space

• fever, anorexia

• reduced milk yield

how do we treat bovine foul in the foot?

3 day systemic penicillin, oxytet or macrolide (topical not effective)

what are sources of infection for bovine foul in the foot?

• environment

• manure

how do we control bovine foul in the foot?

foot bathing with disinfectants