Success Eradicating Footrot from Farms

Follow Dr Deb Lehmann’s unique footrot eradication program to finally remove footrot from your farm.

Footrot is a highly contagious bacterial infection by D nodosus causing acute lameness in sheep. "Climatic conditions on KI this spring are now ideal for footrot-associated lameness to show up and spread" says Deb. With warmth and moisture the footrot bacteria that carried through last summer hidden deep within an infected foot start to multiply. They can then leave the foot to move through moisture films on the pasture and infect the feet of other sheep. Lambs are particularly susceptible as they have thin skin and immature immune systems. Lame lambs at or after marking are often the first indication that footrot has somehow come onto a previously clean property. Footrot occurs worldwide and mainly affects sheep but can also be found in other cloven hooved animals such as goats, cattle and deer. This fact can make eradication difficult on some farms.

Virulent footrot bacteria produce enzymes that can digest the hard hoof causing separation of the sensitive tissues and severe pain. If left untreated this causes limited ability of sheep to walk and graze which in turn leads to failure to thrive despite plenty of feed. This results in weight loss, reduced milk production, reduced wool growth and even death. Less severe strains that do not digest the hoof (benign) can still cause pain and production loss with ideal weather conditions.
 
Footrot bacteria may not express their full capacity to cause under-run of healthy hoof if the weather conditions are not ideal, therefore it is critical to have samples taken from affected sheep and sent to the veterinary laboratory in Adelaide for identification and culture of the bacteria. Once growth occurs a further test called the Elastase Test determines the potential severity of disease that could be caused by the strains present. With virulent footrot the positive Elastase result is  <10 days, intermediate footrot 11-21 days and benign footrot >21 days. Samples can be collected by one of our trained veterinary team at the Veterinary Clinic.
 
Australia leads the world in footrot research especially with the development of flock specific vaccines to successfully eradicate virulent footrot. Dr Deb Lehmann has worked with the University of Sydney since 2005 on vaccine field trials on Kangaroo Island and King Island. Eradication of virulent footrot on most of the trial properties led to commercialisation of the vaccines. Since 2012 Deb has supervised many successful vaccination programs on Kangaroo Island farms.
 
Thorough inspection in the summer following vaccination is critical to remove the 1-2% of sheep that do not respond to the vaccine as well as sheep with other causes of lameness or foot abnormalities. In more recent years a private company in Sydney (Treidlia) has taken over vaccine production from the university and now has ten different strains of vaccine on the shelf. The strains required in the vaccine vary from property to property and can now be identified rapidly by PCR (a DNA test) with samples taken from infected feet. These samples are taken by one of our veterinary team and sent to the University of Sydney. Vaccination is the most successful way to cure and prevent the spread of severe virulent footrot (ie where more than 20% of sheep have under-run and are severely lame).
 
Antibiotics have been given to infected sheep in the past to control infection in spring time. Unfortunately they rarely cure more than 80% of these sheep, do not prevent spread and most importantly tend to hide disease within the feet of some sheep such that footrot re-appears in the next spread period leading to prolongation of the eradication process. This is especially the case with strains of lesser severity (intermediate footrot). Antibiotics have no effect on benign footrot (scald) and are no longer recommended for footrot control on KI.
 
Spring control of all strains of footrot on most farms is best performed by foot bathing known infected mobs 2 or 3 times 3 weeks apart for 1 hour in a 20% solution of zinc sulphate with sodium lauryl sulphate added at a rate of 1% (or 2% if water is hard). This wetting agent causes the curative zinc to be more effective by penetrating 7 times as far into the hoof. Please note that walk through foot bathing has minimal affect on control of virulent strains of footrot but may have an effect as a sterilant of non-diseased feet of clean sheep after passing through contaminated yards or exiting trucks.
 
If you wish to embark on an eradication program then it is best to contact Deb Lehmann at the KI Vet Clinic for advice now during the spread period. We must allow at least six weeks to elapse after the last spring control footbath before the summer inspection to identify and remove sheep with remaining footrot and other causes of lameness. The key to successful eradication of virulent footrot is to have accredited personnel examine every foot of every sheep on the property. This is done once only. Hidden disease is found by trimming every hoof back to a normal shape then using a rotary grinding tool to chase out every crack and remove any shelly wall. In this way, there is nowhere left for virulent footrot bacteria to hide. However we can still be left with benign strains.
 
Benign strains of footrot bacteria can not produce enzymes that digest hoof. They cause lesions confined to the skin between the claws (sometimes called scald as it resembles a burn). These lesions usually heal as the weather dries in summer but the benign bacteria within do not die. Also they are not killed with the spring control program outlined above. The benign bacteria can remain viable within the skin of the foot for many years. Once seasonal conditions become suitable again the bacteria quickly grow and cause the classical scald appearance. These benign footrot bacteria can then spread to other sheep in moisture on the pasture or in yards. It is impossible to differentiate signs seen with benign strains from signs seen with virulent strains early in the course of the disease or if environmental conditions are not suitable for full expression of capacity to cause under-run.
 
For this reason Deb recommends that the 5-day footbath be performed after the summer inspection to eradicate benign strains. This technique that was developed by WA Department of Agriculture 20 years ago showed that benign footrot could be eradicated with repeated foot bathing for 15 minutes each day for 5 consecutive days in a 20% zinc sulphate plus 1% sodium lauryl sulphate solution. This process was never used on commercial properties in WA but has been added on to virulent footrot eradication programs on KI to now successfully eradicate all forms of footrot.
 
The flock is inspected by PIRSA during or after the next spring spread period to confirm that virulent footrot eradication has been successful enabling you to trade sheep to other producers. Deb Lehmann is a PIRSA Approved Independent Assessor to assist with updating your One Biosecurity profile. Your Sheep Health Statement can be completed to show low risk for footrot in sheep being sold from the property.
 
Both benign and virulent strains of footrot cause significant impact on sheep welfare and therefore production. Eradication is possible. Please contact Deb Lehmann at the KI Vet Clinic on 8553 2485 if you wish to discuss further.

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