As foot rot is contagious, it can cost farmers a lot of money due to the time and effort to treat.
Foot scald (benign foot rot/interdigital dermatitis) is caused by the bacteria Fusobacterium necrophorum. This alone causes the inflammation between the toes, but it is not contagious like foot rot.
Foot rot is caused by the coexistence of Fusobacterium necrophorum and Dichelobacter nodosus. Different strains of D.nodosus affect both sheep and goats, and can also be carried by cattle, deer, and horses.
Fusobacterium necrophorum is a natural inhabitant of the large intestine of small ruminants and is found in the soil and manure of pastures. Foot scald and rot outbreaks occur most often when it is cold and wet, as mud and manure has been able to accumulate. The mud and manure causes interdigital irritation and F. necrophorum readily infects the soft, irritated area. Dichelobacter nodosus is only capable of living in the soil for 10-14 days, yet can survive in the hoof for extended time periods given the right anaerobic environment.
These bacteria require irritation of the interdigital area (possibly due to moisture or trauma) in order to gain entry for infections. In addition to this, during the rainy season, infected animals can co timings the soil, which can increase disease transmission to other animals.
Overgrown hooves will also predispose an animal to foot scald or rot. As the micro-organisms can be carried to soil on visitors’ boots, keeping visitors out or requesting then to wear certain boots is a bio security meSure to minimise farm to farm transfer of D.nodosus and F.necrophorum.
Research has shown that genetics help determine whether an animal is resistant or susceptible. The Merino breed is more susceptible, and the Gulf Coast breeds are more resistant.
Boer goats are more susceptible and these are the goats at the farm.
•Reduced weight gain
•Decreased milk and wool production
•Dexreased reproductive capabilities
There is a range of severity in foot rot infections depending on the strain(s) of D. nodosus present.
The virility of the D. nodosus is determined by the amount of protease enzymes they release. This digests the connective tissue between the horn and flesh of the hoof.
Foot scald is characterised by reddened, inflamed tissue between the toes and does not include under-running of the hoof horn.
Virulent footrot is a larger problem as the bacteria will enter the hoof and digest the hard, horn tissue of the sole that protects the fleshy tissue of the hoof. In more virulent strains of footrot, the hard horn of the foot will begin to separate from the underlying tissue about 10-14 days post-infection, producing a foul smell. By 28 days, the horn may become completely detached or attached only at the coronet.