Footrot causes and symptoms

There are 3 elements determining if, and how severely, footrot may appear in a sheep flock:

  • bacteria
  • environment
  • sheep breed.

Bacteria

Footrot is caused by the Dichelobacter nodosus bacteria. For the disease to develop, it must be present in the foot.

This bacteria:

  • lives in the feet of infected sheep
  • can survive in the environment for up to 7 days
  • can live in the foot of an infected sheep for years
  • is generally introduced to a clean flock by infected sheep
  • in some cases, clean sheep walking on contaminated ground or pasture can become infected.

Environment

Moisture can make sheep feet susceptible to infection. These environmental factors cause enough moisture to spread footrot:

  • an average daily temperature of 10 degrees Celsius or higher, for 4-5 days
  • more than 50 mm rain in the preceding month
  • adequate soil moisture over several months
  • sufficient pasture length and density that keeps the ground moist.

Footrot bacteria will die under hot, dry conditions.

Sheep breed

All breeds of sheep can develop footrot, but some are more resistant than others.

  • British breeds: less susceptible.
  • Merinos, Dorpers and Aussie Whites: more susceptible and more severely affected.
  • Younger sheep: more susceptible than older sheep.

Footrot symptoms

The bacterium has many strains ranging from benign to virulent. One property of sheep may have numerous strains of footrot present.

Under the right environmental and host conditions, these strains may express to produce clinical signs – a range of disease severity. However, when conditions are not ideal the virulence of the bacterium may not be reflected in the severity of disease i.e. virulent bacteria will be present, but the severity of disease will appear benign.

Expression of virulent footrot disease includes:

  • chronic and severe lesions
  • lameness
  • loss of production
  • death, in severe cases.

Footrot may express as benign lesions (mild interdigital dermatitis) when:

  • it is early in the disease outbreak – all virulent lesions start as benign (interdigital dermatitis)
  • the climate or host are not favourable for expression
  • treatments have been given to reduce the severity of disease
  • only benign strains are present.

Foot scald caused by D.nodosus is also footrot.

Laboratory testing is the most reliable way to determine the severity of disease, especially when the host and environment are not ideal.

Scoring and reporting footrot

A scoring scale has been developed to rate the severity of footrot infection. The scale ranges from:

  • 0 – no signs of infection
  • 5 – severe footrot.

See photographs to demonstrate each footrot score (PDF 262.5 KB or DOC 11.2 MB)

If you suspect any footrot symptoms, no matter where it may be on the disease spectrum, it must be reported.

Emergency Animal Disease Hotline

Suspected disease or pests in livestock, poultry or aquatic animals must be reported immediately.

Call us to help stop the spread of animal illness, even if you are unsure of the disease.

24 hours a day, 7 days a week

Freecall 1800 675 888
Page last reviewed: 27 Jul 2022

 


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