By Dr. Arron Wise, Reprinted from ORVLA, Vo. 21, No. 1, February 2008
This past summer and fall, several small ruminant and a few camelid clients called concerned about their animals having an ear droop and wanting to circle to one side. Examination of these animals revealed one-sided neurologic signs. In addition, a few of these animals were down and unable to stand. Due to the presenting clinical signs, the top differential was Listeriosis or Circling Disease.
Listeriosis is caused by Listeria monocytogenes. L. monocytogenes can be found in numerous places including the gastrointestinal tract of healthy animals, the soil, and improperly fermented silage. The most likely source of L. monocytogenes in the above animals was the soil. The chance of developing Listeriosis increases if there is an open sore in the mouth, which allows the organism to travel up one of the cranial nerves.
Listeriosis can be seen in animals of all ages. At the onset of the disease, the affected animal may become solitary and crowd into a corner or lean against objects for support. Unilateral or one-sided facial paralysis, circling, trembling of the head, running into objects, drooped ear, salivation, depression and/or an initial fever that may reach up to 107 degrees Fahrenheit are some additional clinical signs to observe for. Listeriosis may even cause some late term abortions. Transmission from animal to animal is highly unlikely.
The treatment for Listeriosis can be difficult and not all animals will respond to antibiotic treatment. If a course of antibiotics is attempted, it is recommended that high doses of an appropriate antibiotic be used. Tetracycline antibiotics and penicillin antibiotics have been used to treat Listeriosis. In consulting with the other doctors in our practice, we feel that high doses of penicillin are more effective than the tetracycline antibiotics. However, please consult your veterinarian for his/her professional opinion, because in some regions, tetracycline antibiotics may be more effective than penicillin-based antibiotics. Supportive therapy, such as intravenous fluids or oral fluids may need to be administered to those individuals who have difficulty eating and drinking.
In conclusion, Listeriosis can cause severe neurological signs and may even be fatal to the affected animal. However, transmission between animals is very difficult. If the treatment regimen is going to be successful, please consult with your local veterinarian as soon as possible.