Foot rot in sheep and goats is caused by a synergistic infection of two bacteria; Fusobacterium necrophorum and Dichelobacter nodosus. It causes much economic hardship, and is one of the reasons many people caution against buying animals from unknown sources, such as through an auction house. Once established on the farm, the disease is it difficult to eradicate.
To minimize the risk of introducing it to your farm, any animal purchased should be quarantined for several weeks to prevent the spread of foot rot and other chronic diseases.
During the quarantine, the animal’s feet should be trimmed and examined closely for pockets and other malformations that suggest a previous D. nodosus infection. Vehicles such as trucks and trailers or facilities in which unknown or infected animals have been held should be thoroughly cleaned and disinfected before placing uninfected animals in them. If it is not possible to thoroughly disinfect transport vehicles, zinc sulphate can be liberally scattered over the floor to reduce viable bacteria.
BACTERIA NO. 2
The bacteria Fusobacterium necrophorum is a natural inhabitant of the large intestine of small ruminants and is found normally in the soil and manure of pastures or feedlots. Infection is exacerbated by cold, wet conditions where mud and manure have been allowed to accumulate. The mud and manure causes irritation between the toes of the animals, and F. necrophorum readily infects the soft, irritated area. Alone this bacterium is not capable of causing foot rot. It causes a condition called foot scald. When Dichelobacter nodosus joins the party is when foot rot occurs. This bacterium is only capable of living in the soil for 10 to 14 days, yet can survive in the hoof for extended time periods given the right anaerobic environment. The ideal temperature for growth is between 10 and 20 C making this an greater issue in early summer under moist conditions.
The incubation period of foot rot is about 14 days. European countries still regularly use the foot bath at 10-day intervals to control spread of the organism in affected flocks in wet conditions. Foot rot has been controlled by placing foot baths with a zinc (0.10 per cent w/v) sulfate solution around water troughs, forcing sheep to walk through and stand in the baths in order to drink. Most Canadian producers depend on antibiotics and nutritional controls for their animals.
Research has shown that D. nodosus vaccines accelerate healing in affected sheep and aid in protecting unaffected sheep. They are recommended as an additional tool to be used when trying to control or eradicate the disease. However, their effectiveness depends on the bacteria strain(s) causing the infection and those present in the vaccine. No vaccine contains all the various strains of D. nodosus.
Alum-precipitated vaccines require two doses four to six weeks apart to establish effective immunity, which persists for two to three months. Lesions heal within four to six weeks if immunity is established.
Oil emulsion vaccines induce immunity within three weeks of the initial dose and may persist for three to four months. In endemic areas, revaccination is recommended at three and six months. Adverse reaction to the vaccine is common, resulting in large granulomas and occasional abscesses, therefore most producers do not use them. Most sources have reported a 60 to 80 per cent success when using the D. nodosus vaccine along with regular foot trimming and attention to housing sanitation. Vaccines for F. necrophorum have not generally shown much benefit in either treatment or prevention.
ZINC MINERAL CAN HELP
Attention to the animals’ mineral supply will also help minimize foot rot outbreaks. It is important to read the labels and verify that zinc is present. Mineral supplements have been reported effective in reducing hoof rot in cattle, but has not been shown to be particularly helpful for sheep foot rot. However, zinc is important for immunity and skin/hoof health. Providing zinc in a well-balanced trace mineral mix may be helpful in locations deficient in zinc.
Baby season is a good time to assess each individual animal. This is when we worm the dam, give vitamins required and check their overall soundness. Four weeks prior to having their young the goats/sheep are vaccinated and given vitamin A and D, but depending on weather we don’t like to stress them any more than necessary by also checking feet. If we find one of the small ruminants in need of foot attention it is dealt with then. Winter is a recommended time of year since the ground if frozen. There is little chance of the offending bacterium that may be present in the soil colonizing in a freshly trimmed hoof.
For more information visit the Food and Agriculture Organization of the United Nations website along with a sheep health online manual.
When trimming the hooves, if a problem is found it is best to trim off all the offending tissue and paint the area with Kopertox. In fact, we have had success with goats just trimming up the hoof and applying Kopertox without the need for antibiotics.
Over the years we’ve never had many animals with foot rot but know plenty of people who have. Prevention seems to start with not buying strange animals without quarantine. The rest of the prevention relies on keeping up the overall immune system of the livestock, a bit of work trimming hooves and cleaning pens, and supplying a proper mineral mix for the stock. These measures will go a long way to ensure this problem doesn’t occur on your farm. It will also help to limit the problems if they do arise.†
Debbie Chikousky farms with her family at Narcisse, Manitoba. Visitors are always welcome. Contact Debbie at [email protected]