Vaccinate to help eradicate footrot
A vaccine is now registered for use across Australia that will assist producers to eradicate virulent footrot from their sheep flocks.
This provides an alternative to the use of antibiotics in limiting the number of sheep to be culled during the summer program of eradication by repeated inspections, which is necessary to get rid of this nasty scourge.
At the June 2017 BESTWOOL/BESTLAMB conference in Bendigo, Dr Bruce Jackson from Tasmania described how to apply this new technology. This was based on his experience using experimental vaccines that the commercial vaccine is based on. This is a summary of his advice.
The previously available commercial vaccine contained 10 serogroups of the bacterium Dichelobacter nodosus. However, with this many serogroups present, the vaccine was, at best, only able to control the disease.
By limiting the number of serogroups in the new vaccine to only one or two (customised for the sheep on your farm), a stronger and longer-lasting immunity is developed in vaccinated sheep. This means up to 95% of infected sheep can be completely cured.
The challenge in using this new vaccine is in identifying which serogroups exist in the bacteria on your sheep's feet, and which ones need to be in the vaccine.
About half of farms with virulent footrot only have two key serogroups that need to be used in the vaccine — the remainder have more. With only two serogroups in any vaccine batch and two doses needed for each batch to work, the number of serogroups needing to be controlled affects the cost and duration of the vaccination program before eradication can commence the next summer, because each different batch is administered after the previous one has successfully worked (three months later).
There is also a cost for the laboratory testing to work out which serogroups to include in your vaccine batches. If luck is on your side and only modern PCR techniques are needed, that cost may be as little as $1200. However, it could be as much as $3200.
Bruce suggests targeting your sample collection (10 swabs are needed from affected feet) by only sampling from sheep with the worst feet. This maximises your chance of getting the right mix in your vaccine batches. A two-serogroup vaccine retails for $2.12 per dose, and two doses are needed 4 to 6 weeks apart. Most sheep are cured within a week or so of the second dose.
As the vaccine is available on a veterinary prescription, have your veterinarian do the sample collection for you.
Questions to ask when eradicating footrot
- What is the risk of reinfection, wasting all your hard work? What is the likelihood of infected sheep straying onto your property, and of you achieving clean musters? Do you frequently trade sheep, buy store lambs or offer agistment?
- Do you have the right facilities, including sheep handlers (or can your footrot contractor supply them)? Is your internal fencing secure enough to keep the dirty 'infected' mobs separate from the inspected 'clean' mobs until the dirty ones are culled?
- Do you have the time, labour and money to carry through with the program?
A hint for a better chance of success is to always seek the assistance of someone knowledgeable in managing footrot eradication programs.
For a summary of Bruce's presentation, please visit the BESTWOOL/BESTLAMB.