Caseous-Lymphadenitis Management in Sheep

Cause and Spread

• Caseous lymphadenitis in sheep is caused by the corynebacterium pseudotuberculosis bacteria. These bacteria are spread through direct contact. Sheep can become infected by contaminated soil, feed and water containers, and surfaces in shelters where healthy and infected sheep congregate. These surfaces most commonly become contaminated when a ruptured abscess on an infected sheep drains onto them, spreading the bacteria. Once the bacteria enter the sheep's body, either orally or through open wounds, they enter the bloodstream, spread throughout the body and multiply. These bacteria cause abscesses on the lymph nodes and internal organs. An animal infected with CL will be a carrier of the disease for life.

Symptoms

• Abscesses are the most noticeable symptom of Caseous Lymphadenitis infection. External abscesses may form behind the animal's ears, under the jaw, on the shoulder or between the hind legs. These external abscesses are responsible for spreading the disease. In some cases, no external abscesses form, instead concentrating on the internal organs. These internal abscesses result in the sheep's death, and often the cause of death is not known until a postmortem examination reveals the abscesses. Chronic weight loss is often the only outward sign of CL infection when no external abscesses are visible.

Diagnosis

• Because CL is not the only condition that can cause abscesses or chronic weight loss in sheep, diagnosis can be difficult. If you suspect an animal in your herd has CL, you should take a sample of the pus from an abscess and give it to your veterinarian to test for the corynebacterium pseudotuberculosis bacteria.

Treatment

• Antibiotics do not have any effect on a Caseous Lymphadenitis infection. The only treatment you can provide your animals is treatment of the visible abscesses. You should isolate any sheep you find with an abscess. Wearing disposable rubber gloves and using a disposable scalpel, you should lance the abscess and drain it in the isolation pen. Draining the abscess in the isolation pen prevents it from rupturing on its own in the pasture and causing contamination and spread of the bacteria to the rest of the herd. This is a good time to collect some of the material from the abscess to submit for testing. Once the abscess has drained, you'll need to rinse the cavity thoroughly with hydrogen peroxide; then flush it with iodine. You should keep this animal isolated until the wound heals completely. Burn your gloves, paper towels and other materials used to clean the abscess immediately after use and disinfect the isolation pen to prevent recontamination.

Prevention

• Because no effective treatment for CL is available, prevention is your best means of control. A vaccine made from killed germs is available; discuss options with your veterinarian. Look over sheep you plan to purchase carefully, and avoid bringing home any animal with visible abscesses or scars from abscess draining. You should visually inspect your herd daily, looking for abscesses. During vaccination or other whole-herd treatments, use a new needle for each animal to keep from spreading the corynebacterium pseudotuberculosis bacteria from carriers to healthy sheep. You should thoroughly disinfect any equipment that can break the skin of your sheep, such as ear taggers. This is particularly important for wool shears, as the shearing process can cause rupture of an abscess hidden by the sheep's thick wool.