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In a review of 159 archived bovine autopsy cases submitted to the Georgia Veterinary Diagnostic Laboratory System from 2001 to 2017, we evaluated histologic lesions and other laboratory test results in cases diagnosed with central nervous system (CNS) disease to determine the most common disorders and the rate of definitive morphologic and etiologic diagnosis within the population. The most common breed was Aberdeen Angus or Angus (31%), and female animals comprised 60% of the overall submissions. Gross anatomic changes were described in 33% of cases that had histologic lesions. Suppurative meningoencephalitis was the most common diagnosis (28% of cases overall) and was frequently associated with bacterial sepsis. Lymphocytic meningoencephalitis without an identified etiology was diagnosed in 17% of cases. Polioencephalomalacia was the most commonly identified noninfectious diagnosis (17%). Hydrocephalus was the most common CNS comorbidity and potential congenital defect. Identification of specific agents was sporadic, and infectious disease testing was largely dependent on fluorescent antibody testing, almost all of which were negative. Our findings indicate the common differential diagnoses for cattle with neurologic signs in the southeastern United States, as well the need for a well-defined, methodical diagnostic approach, including autopsy, histology, and appropriate additional laboratory testing.

Listeriosis is a disease of humans and domestic mammals (mainly ruminants) with variable manifestations, primarily encephalitis, septicemia, and abortion. Although Listeria monocytogenes readily causes illness in ruminants, the prevalence among domestic South American camelids (llamas and alpacas) is low and has not been documented in their wild counterparts, the vicuna and guanaco. We describe herein the clinical signs, autopsy findings, and histopathology of septicemia and suppurative meningoencephalitis caused by L. monocytogenes in 2 neonatal llamas ( Llama glama) from the same herd. L. monocytogenes was isolated in pure culture and identified by real-time PCR on fresh and paraffin-embedded tissue samples of the brain from both crias. This presentation of septicemic listeriosis with meningoencephalitis in 2 animals from the same group is unusual, especially among llamas.

A four-year-old intact female pointer dog from a hunting plantation in South Georgia, USA, developed acute neurological signs. The referring veterinarian suspected rabies or pseudorabies; the dog was euthanased and submitted to the Tifton Veterinary Diagnostic and Investigational Laboratory for necropsy. No gross anatomical changes were present. Portions of brain were submitted for rabies virus fluorescent antibody test with a negative result. Histopathology revealed a marked lymphoplasmacytic meningoencephalitis with numerous intracytoplasmic eosinophilic inclusions within neurons, still raising concerns for rabies meningoencephalitis. Rabies immunohistochemistry was then performed on the brain, yielding a negative result. Brain samples were also negative for canine distemper virus and herpesvirus (pan-herpesvirus primers) PCR. Electron microscopy did not reveal viral particles within the inclusions. Similar intraneuronal pseudoinclusions have been previously reported in non-rabid dogs and cats. Such inclusions are a diagnostic challenge, especially in animals with central neurological signs and/or meningoencephalitis.

A nine–year-old female neutered Somali cat presented with a one-month history of weight loss and inappetance. Thoracic radiographs revealed an extensive cranial mediastinal mass, and fine needle aspirate cytology and core needle biopsies were initially suggestive of a thymoma. The mass was excised via a mid-ine sternotomy and partial pericardectomy. Clinical signs recurred four weeks postsurgery and investigations revealed recurrence of a mediastinal mass, pleural effusion and an additional small mass cranial to the right kidney. Histopathological examination and immunohistochemistry of the previously resected mass prompted a revised diagnosis of histiocytic sarcoma (HS) with abdominal metastasis. The cat was treated with doxorubicin and lomustine but did not respond well and was euthanased two months later. HS is an uncommon neoplasm in cats with only two cases of mediastinal involvement reported in the literature. This case underlines the importance of immunohistochemistry in the evaluation of mediastinal masses.