Managing virulent footrot in sheep and goats in Western Australia

Footrot scoring system

Advanced virulent footrot is a painful condition that causes production loss. A scoring system from zero to five has been developed to help farmers and inspectors to categorise footrot lesions. Below are photos that illustrate each score.

Score 0 = normal foot

Score 1 = mild inflammation including moisture, reddening and hair loss of the skin between the toes

Score 2 = mild inflammation including moisture, reddening and hair loss of the skin between the toes, and tissue damage of the soft horn of the inner wall

Score 3 = under-running and moderate tissue damage of the inside wall and the sole

Score 4 = under-running and more severe tissue damage reaching the outer edge of the sole

Score 5 = very severe tissue destruction with under-running reaching deep layers of the outer wall and the toe

Severity of virulent footrot

The severity of virulent footrot lesions depends on three factors:

• the susceptibility of the animal
• environmental conditions
• the strain of bacteria.

If conditions are not favourable to the bacteria, then virulent footrot strains may only cause mild changes. Less severe forms may involve only the soft horn of the inside wall and the sole (score 1 and 2 lesions). This is why it is so important to take a swab from between the toes store in appropriate media, obtained from the Department, and to test at the Department's diagnostic laboratories, rather than rely only on visual signs.

How virulent footrot spreads

Infected sheep or goats are the main source of new infections and some will maintain the infection from year to year.

The bacteria can survive in deep, unexposed lesions in the foot from one season to the next, but when away from the foot, survival time on the soil is quite short. Hot, dry conditions cause bacterial death in a few hours, while in warm, wet conditions the bacteria can survive a maximum of 7–10 days. During dry periods there is minimal spread of disease. Most of the affected feet appear to heal; any bacteria that are shed will die, and they are unlikely to invade and cause damage to uninfected feet.

When conditions become wet however, the previously ‘dried out’ lesions in the feet of the chronically infected animals may become active with large numbers of bacteria being shed. Wet feet of clean sheep are then easily infected.

The disease spreads rapidly during warm (average daily temperatures above 10 degrees Celsius) and moist conditions, usually in early spring to summer. Lesions may develop during wet autumn and summers or where sheep can access surface water year round.

Although reports are rare, the disease may be spread mechanically, either on the feet of other animals, or by people transferring contaminated mud on boots. This transfer is more likely within an infected property than between properties. Unwashed livestock transport trucks and sheep handling equipment may occasionally contribute to the spread of footrot.

In a small number of cases, cattle have been known to be infected with virulent footrot and able to spread footrot back to the sheep.

Quarantine restrictions

Flocks diagnosed with virulent footrot are issued with a Pest Control Notice, which restricts movements of sheep and goats from these properties until the infection has been eradicated.  A Department Biosecurity or Veterinary Officer will help to plan an eradication or control program on the property with the property manager. 

Under the Pest Control Notice, sheep may only move directly to an abattoir or export feedlot, and all movements must be notified in writing to the DPIRD case manager. Lame sheep cannot be transported.