Foot Rot

FOOT ROT Foot rot, or infectious pododermatitis, is a hoof infection that is commonly found in sheep, goat, and cattle. As the name suggests, it rots away the foot of the animal, more specifically the area between the two toes of the affected animal. It is extremely painful and contagious. It can be treated with a series of medications but if not treated the whole herd can become infected. The cause of the infection in cattle is two anaerobic bacteria (bacteria that can grow without oxygen), Fusobacterium necrophorum and Bacteroides melaninogenicus. Both bacteria are common to the environment that cattle live in and Fusobacterium is present in the rumen and fecal matter of the cattle. Usually there is an injury to the skin between the hooves that allows the bacteria to infect the animal. Another cause of foot rot may be high temperatures or humidity causing the skin between the hooves to crack and let the bacteria infect the foot. This is one of the reasons that foot rot is such a major problem in the summer. Foot rot is easily identifiable by its appearance and foul odor. Treatment is usually with an antibiotic medication, and preventing injury to the feet is the best way to prevent foot rot. Cause Footrot is caused by a synergistic reaction between two organisms -Fusobacteria necrophorum and Bacteroides nodosa -in the foot. One of them, Fusobacteria necrophorum, is nearly always present in the environment. The other, Bacteroides nodosa, can survive a maximum of two weeks if not residing in the hoof. Bacteroides nodosa produces a powerful enzyme that destroys the tissues of the hoof by migrating through the soft tissues to areas under the horn. One or two weeks of wet feet and hot humid conditions creates an ideal environment for footrot-causing bacteria to grow. Foot injury caused by rough concrete and other hard surfaces may also wear the hoof down, leading to easy bacteria entry and growth. Cause: Mechanical injury or softening and thinning of the interdigital (between the toes) skin by puncture wounds or continuous exposure to wet conditions are necessary to provide entrance points for infectious agents. Fusobacterium necrophorum is the bacterium most often isolated from infected feet, but is also frequently isolated from non-diseased interdigital skin. The majority of F. necrophorum isolated belong to biotypes A and AB

which produce toxins that cause necrosis (decay) of the infected tissues. F. necrophorum is also isolated from liver abscesses in feeder cattle, necrotic stomatitis in calves and calf diphtheria. F .necrophorum appears to act cooperatively with other bacteria such as, Bacillus melaninogenicus, Staphylococcus aureus, Escherichia coli, Actinomyces pyogenes thereby decreasing the infective dose of F. necrophorum necessary to cause disease. Bacteroides nodosus, the organism causing foot rot in sheep, may cause an interdigital skin surface infection in cattle allowing entrance of F. necrophorum, thereby causing disease. Transmission: Feet infected with F. necrophorum, serve as the source of infection for other cattle by contaminating the environment. Disagreement exists on the length of time F. necrophorum can survive off of the animal, but estimates range from 1 to 10 months. Once loss of skin integrity occurs, bacteria gain entrance into subcutaneous tissues, begin rapid multiplication and production of toxins that stimulate further continued bacterial multiplication and penetration of infection into the deeper structures of the foot.

Clinical Signs Lameness will be observed from time to time in all flocks. This may result from foot injury, foot breakage, sheep fighting around feed bunks, rams butting ewes, sharp objects stuck in the hoof, mud, brittle hooves cracking, and injury to other joints in the legs. In more advanced cases, the foot will be red, swollen and appear moist or grayish-yellow when examined. The foot will also be sensitive when pressure is applied. Signs of Infection The first sign of a foot rot infection is when the skin between the claws of the hoof begins to swell. Swelling usually appears twenty-four hours after infection. The skin between the toes may be very red and tender and the toes may separate because of all the swelling. This is very painful to the animal and can cause lameness. A crack can develop along the infected part and is yellow in color. The foot will have a foul odor. tendons, and joints in the

area can become infected which is much harder to treat. There is a condition known as super foot rot that is seen in some animals. Super foot rot is just like normal foot rot only infection occurs much faster and is usually much more severe. Most normal foot rot treatments will not cure this foot rot and a veterinarian should be contacted immediately. Treatment The best way to treat foot rot is to catch it as early as possible. The infected animals should be separated away from the herd as soon as possible to prevent the infection from spreading and allow the animal a better environment for healing. The first treatment is to clean the foot thoroughly and examine the foot to determine that it is definitely foot rot that is causing the infection. Keeping the wound clean and using an antibiotic ointment may help reduce the spread of infection. Foot rot is usually treated with an antimicrobial product. Penicillin, tetracycline, and other antibacterial medicines are often used to treat normal cases of foot rot. Usually the antimicrobial product is non-prescription but sometimes a veterinarian may choose to use a prescription medication. It is critical to closely monitor the animals to make sure they are responding to treatment. The infected animals should be kept dry until the healing has occurred. If the animal is showing no signs of recovery after three to four days the bacteria could have infected the other tissues of the foot and along with a veterinarian the owner should decide whether to amputate the bad foot or to put the animal down Prevention The infected animals can serve as the source of infection for the whole herd because they will spread the bacteria throughout the environment. The bacteria can live without a host for one to ten months. Once another animal gets a cut or crack in the soft tissue between their toes the bacteria can infect the animal. This is why infected animals must be kept away from the rest. A good way to prevent foot rot is to keep any foreign objects that may cut or damage the foot out of the environment. This should be a practice regardless of whether a herd has foot rot or not. The cuts are what allow the bacteria to enter the foot tissue and cause the infection. Some cattle feeders add zinc to the feed mixes and may vaccinate the animals for foot rot. Zinc is important to maintaining the skin and hooves of cattle. Cattle deficient in zinc will become infected easier than cattle with adequate zinc in their diet. Limitations to Treatment

Sheep treated in footbaths of zinc sulfate, copper sulfate or formalin for footrot should not be allowed to walk through the solutions and back through muddy areas or on grass wet with dew. This will dilute the compounds on the feet and render the treatment ineffective. Lame sheep should be separated from healthy sheep to retard the exposure to the bacteria causing footrot. Sheep not responding to the foot bath in two weeks following treatment should have feet trimmed very closely (bleeding may occur) and a topical spray applied after the bleeding stops. The feet must be trimmed down to the healthy tissue if treatment is expected to be effective. Sheep not responding to treatment following footbaths and trimming with topical application should be culled. Otherwise, they will remain as carriers and affect the healthy flock. Cull all mature animals with deformed feet, they probably are carriers. It only takes one carrier in a flock to continuously spread infection to other sheep in the pasture or drylot. How to Prevent Footrot When purchasing sheep, never buy from a flock in which you have observed lame sheep. Bring newly purchased sheep home and keep them confined for two or three weeks and observe for lameness. If the animals begin to limp, examine the feet and treat for footrot by trimming closely and applying a topical spray of 10% formalin, 20% copper sulfate or 10% zinc sulfate. If they continue to show signs of lameness, contact the person from whom you purchased the animals to negotiate with them or sell the animals rather than expose the entire healthy flock. A Systematic Treatment Plan To Eliminate Footrot 1. Separate all lame sheep from the flock. 2. Run the non-lame group through a 10% formalin footbath and relocate to a pasture or lot previously unoccupied for 14 days. 3. Treat affected lame sheep by running them through a footbath containing 10% zinc sulfate to reduce the percentage of affected animals when the number is large and labor availability critical. 4. Place the footbath in a strategic area where the infected sheep will walk through it several times a day.

5. When the number of affected animals is small, feet should be trimmed prior to exposure to the footbath. 6. Approximately 75% of the affected feet will be completely healed without trimming within four weeks, if feet remain dry following footbath treatment. 7. Remaining affected animals will require individual treatment of trimming feet to expose diseased areas and subsequent treatment with a topical 10% formalin spray. 8. Run animals through clean 10% zinc sulfate footbath for two more weeks. 9. Animals not responding to treatment should be sold. 10. Purchased animals should have feet trimmed and treated topically with 10% zinc sulfate, and isolated for two weeks before introducing to the existing flock.