Brain Abscesses

Dr. Steven Parish

(Reprinted from Pygmy Goat WORLD magazine with permission)

A 4-month-old female Pygmy goat was presented with a history of chronic abnormal behavior. The young female had varying complaints including depression, reluctance to lay down, hunched-up appearance as if in pain, unusual vocalization and head pressing. Upon presentation to the clinic, the animal was noted to be head pressing, the head was turned to the right, and it was questionable if she could see from the right eye. The results of physical examination suggested a problems in the nervous system and because of the clinical signs, a tentative diagnosis of right sided brain disease was made. Analysis of peripheral blood examination revealed an inflammatory and possibly infectious state in the goat. To further the diagnosis, a cerebrospinal fluid sample was obtained. Results of this indicated at least a meningitis (inflammation around the brain and spinal cord) was present.

Based on the chronic nature of the problem, previous failure to respond to treatment and grave prognosis, euthanasia was elected. The goat was submitted for a complete postmortem examination. Lesions were confined to the nervous system. A menigitis was present. Also present were two large abscess in the right hemisphere of the cerebrum. The larger of the two abscesses was 2 cm in diameter. A pure culture of Actinomyces pyogenes was derived from the abscesses. It was easy to say that the neurologic signs in this animal were attributable to the brain abscesses.

Brain abscesses occur sporadically in goats. Infectious agents can reach the brain in several ways. First, infection can be spread through the blood stream, what is termed a bacteremia. One of the most common times for a bacteremia to occur is in the early days of life. There is a close relationship between passive transfer of colostral antibodies and prevention of bacteremias. Animals with failure of passive transfer are much more likely to develop a bacteremia than those with successful passive transfer.

A more common scenario to bactermia is joint ill, where multiple joints become infected. None were seen in this animal. Also, animals may become bacteremic during other infectious episodes, such as pneumonia.

A second mode of spread of bacteria to the brain can come from local invasion of bacteria. Inner ear infections and sinus infections are possible primary sites.

One other, possibly important source, is the process of disbudding. When the hot iron is applied to the horn bud, the purpose is to destroy tissue. Fortunately, we rarely see adverse consequences. However, this author has seen several young kids who developed acute neurologic disease from disbudding. At postmortem, both surfaces of the cerebrum of the brain, just under where the horn was, had severe hemorrhagic lesions. Therefore, it is possible that dehorning can, on rare occasions, allow for enough tissue damage for infection to spread this way to the brain.

Brain abscesses must be differentiated from other causes of brain disease such as encephalitis, tumors, abnormal parasite migration, ear infections, lead poisoning and polioencephalomalacia. In this case, the abnormal CSF tap indicated a chronic infection in the nervous system. A chronic meningitis and possible brain abscess were considered. The ultimate diagnosis would have involved a Cat-scan and biopsy of the areas. For multiple reasons, these diagnostic techniques were not undertaken. Fortunately, abscesses in the nervous system are rare. Unfortunately, once they are discovered or suspected, the prognosis is usually grave.

 
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