Footrot in sheep is a highly infectious and contagious disease found in sheep. Deer and goats are able to become infected with footrot bacteria. However, they rarely show the same degree of symptoms as infected sheep. Fatalities are rarely an occurrence in sheep with Foot Rot although with the resultant lameness economic loss results from an inability to access food. This means that the sheep are unable to grow and develop to their full potential.
Foot Rot in sheep is caused by two bacteria known as Bacteroides nodosus, which are persistently present in the environment, and Fusobacterium necrophorum, which can only survive for a fortnight outside of the host. Both bacteria are required to interact together for Foot Rot to occur.
The pathogen affects the inter-digital skin and the deeper layers within the hoof. This includes the heel and sole. Sheep are more susceptible to the disease if they graze on wet and damp land or live in an indoor environment which is also wet and damp in condition. Different breeds of sheep have varying degrees of susceptibility.
The bacteria can be transmitted into the foot via exposure to contaminated faeces and soil. The characteristic sign of Foot Rot in sheep is generally lameness due to the painful results following infection of the disease as well as an unpleasant smell coming from the foot. Vaccines are available to reduce the severity of the signs and symptoms following infection.
Transmission of Footrot
Foot Rot bacteria can be transmitted via contact with infected material. This can include contaminated bedding, faeces, and most areas of ground walked upon. They transfer to the feet of animals which are more susceptible if the feet are warm and wet. Areas such as sheep transporting vehicles are also able to act as sources of infection.
Bought in animals infected with the disease are able to transfer the bacteria to the farm when introduced to new flocks. It has been suggested that recovered sheep from this infection are able to carry the bacteria in their feet for a period of time and therefore this aids in the spread of the disease.
The Bacteroides nodosa bacteria are able to survive outside the host in the soil for as long as two weeks. They can also survive this long in the infected sheep’s hoof. On the other hand, Fusobacterium necrophorum is extremely prevalent and resistant so can survive for very long periods of time outside the host, in the environment. Favourable environmental conditions are warm and damp, thus leading to rapid multiplication of the bacteria and an increased risk of infection.
Signs and Symptoms of Foot Rot
Initially, the sheep may not present any signs or symptoms at all. There may be inter-digital redness and moisture. Swelling may be presented. The horny tissues become separated and the foot will smell, as is suggested in the name, rotten and unpleasant. Generally, most cases of Foot Rot will result in lameness. More than one foot may become infected. If these include both front feet then the sheep will often kneel to relieve pain or lie down and be reluctant to move. Severe infection increases the degree of the original symptoms as well as introducing a yellow tinge to the foot. The disease may look similar to and be mistaken for foot scald.
As a result of lameness, the sheep may find it too painful to move towards any feed. This will result in a loss in weight and a loss in body condition. Ewes may produce a lower amount of milk which will also adversely affect the condition of their lambs. Rams may experience a drop in fertility and so lamb numbers will also drop.
Treatment for footrot
Foot Rot can be treated to individual severe cases using antibiotics if it is diagnosed early enough. Pencilling may be injected as part of this treatment plan. The sooner it is diagnosed and treated, the more rapid the recovery. The infected animals should be made to recover in dry environments where the bacteria cannot thrive. In some cases, the severely infected tissue may need to be surgically removed.
Foot baths consisting on precise measurements of copper sulphate and zinc sulphate solutions are available to be regularly used provided the sheep are previously run on slats or stones to prevent contamination with faeces or soil found on their feet. The animal should have its feet soaked with these solutions for an hour daily. Dilution of the solution can occur if the animals are allowed to return to muddy or wet pastures and so this should be avoided. It is important to disallow any drinking of this toxic solution.
Prevention of Foot Rot
Food Rot can be prevented from spreading by using a few simple preventative measures. Good hygiene, bacteria removal, and vaccination are included here.
Lime can be spread over pens in order to eliminate the presence of the bacteria. Foot baths can be used to destroy the causal bacteria. Closed in flocks are less likely to have such a high incidence of Foot Rot. Pastures should be prevented from becoming long and rough, so as to prevent abrasions to the feet and so easy access for bacteria to the inside of the foot. Vehicles used to transport sheep should be disinfected.
Bought in sheep should be observed for signs of lameness or infection and not bought if these are present at the time of buying. Following bringing new sheep to the farm, they should be isolated for a period of time for observation before being introduced to the flock. Housed sheep have an increased risk of spreading disease so infected animals should be preventing from coming into contact here. Infected animals should be isolated in dry environments so that unaffected animals cannot become infected. Some farms prevent the spread of the disease by culling infected adult sheep or sheep with deformed feet. Areas which have been in contact with infected sheep should not be used for a minimum of fourteen days.
Vaccines are available to prevent the spread of Foot Rot infections. These do not prevent infection but do significantly reduce the severity of the signs and symptoms. It is suggested that new animals should be vaccinated prior to introduction to the flock. Booster vaccinations before predicted outbreaks, such as the wetter months, can be given to provide long term protection against foot rot.
Diagnosis of Foot Rot
Differential diagnoses can be made once lameness is observed and so veterinarians should be contacted for advices. Otherwise, the disease may be mistaken for laminitis, foot scald, or abscesses. A correct diagnosis results in a correct and therefore more cost-effective treatment plan. Blood samples may be taken to determine and confirm the presence of the bacteria Bacteroides nodosus.
Prognosis of Footrot
The general result of footrot is a high severity in sheep lameness. The results are a loss in growth production for farmers and this can lead to large economic losses. There may be a decrease in the number of lambs and in the amount of wool that is produced.