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In collaboration with the American College of Veterinary Pathologists

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.

An adult-onset generalized canine demodecosis is a life threatening form of demodecosis often seen in immunocompromised dogs. A generalized, adult-onset canine demodecosis with an unusual vascular invasion, thrombi and dissemination to peripheral, and visceral lymph nodes was diagnosed in an adult, female, American Bulldog of unknown age. Organized thrombi with intralesional mites were observed in multiple lymphatic vessels and in a section of blood vessel. Vascular invasion of mites with dissemination of mites into visceral lymph nodes, is an unusual findings not previously recorded in canine generalized demodecosis. Dissemination of mites to visceral lymph nodes through vascular channels may be part of the pathogenesis of chronic, untreated, and disseminated, adult-onset generalized canine demodecosis.

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.

The laboratory diagnosis of infectious diseases, especially those caused by mixed infections, is challenging. Routinely, it requires submission of multiple samples to separate laboratories. Advances in next-generation sequencing (NGS) have provided the opportunity for development of a comprehensive method to identify infectious agents. This study describes the use of target-specific primers for PCR-mediated amplification with the NGS technology in which pathogen genomic regions of interest are enriched and selectively sequenced from clinical samples. In the study, 198 primers were designed to target 43 common bovine and small-ruminant bacterial, fungal, viral, and parasitic pathogens, and a bioinformatics tool was specifically constructed for the detection of targeted pathogens. The primers were confirmed to detect the intended pathogens by testing reference strains and isolates. The method was then validated using 60 clinical samples (including tissues, feces, and milk) that were also tested with other routine diagnostic techniques. The detection limits of the targeted NGS method were evaluated using 10 representative pathogens that were also tested by quantitative PCR (qPCR), and the NGS method was able to detect the organisms from samples with qPCR threshold cycle ( C T ) values in the 30s. The method was successful for the detection of multiple pathogens in the clinical samples, including some additional pathogens missed by the routine techniques because the specific tests needed for the particular organisms were not performed. The results demonstrate the feasibility of the approach and indicate that it is possible to incorporate NGS as a diagnostic tool in a cost-effective manner into a veterinary diagnostic laboratory.

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.

Case Description—A 7-year-old Quarter Horse gelding was hospitalized in Ocala, Fla, because of lethargy, fever, anorexia, and swelling of distal aspects of the limbs. A tentative diagnosis of equine piroplasmosis (EP) was made on the basis of examination of a blood smear. The case was reported to the Florida State Veterinarian, and infection with Babesia equi was confirmed. The subsequent investigation included quarantine and testing of potentially exposed horses for B equi and Babesia caballi infections, tick surveillance, and owner-agent interviews. Clinical Findings—210 horses on 25 premises were tested for infection with EP pathogens. Twenty B equi–infected horses on 7 premises were identified; no horses tested positive for B caballi. Seven horses, including the index case, had clinical findings consistent with EP Dermacentor variabilis was considered the only potential tick vector for B equi collected, and all D variabilis specimens tested negative for Babesia organisms via PCR assay. Results of the epidemiological investigation suggested that B equi was spread by use of shared needles and possibly blood transfusions. All horses that tested positive were involved in nonsanctioned Quarter Horse racing, and management practices were thought to pose substantial risk of transmission of blood-borne pathogens. Treatment and Outcome—Final outcome of B equi–infected horses was euthanasia, death from undetermined causes, or shipment to a US federal research facility. Clinical Relevance—This investigation highlights the importance of collaboration between private veterinary practitioners, state veterinary diagnostic laboratories, and regulatory officials in the recognition, containment, and eradication of foreign animal disease.