Bovine Astrovirus and its Potential Role in Bovine Lymphocytic Encephalitis

dc.contributor.advisorCaswell, Jeff
dc.contributor.authorComeau, Dominique of Pathobiologyen_US of Guelphen of Veterinary Scienceen_US
dc.description.abstractAstroviruses are a well-known cause of gastroenteritis in humans and many domestic animals. More recently, they have emerged as a cause of encephalitis in cattle and other species. Encephalitis is an economically important disease in cattle due to the death of animals. There is a zoonotic concern as many causes of encephalitis in cattle can cause disease in humans. It is therefore essential to determine the causes of encephalitis and their relative importance in a population. This study sought to determine the frequency of bovine astrovirus infection in cases of encephalitis in adult cattle in Ontario and to examine the pathologic findings in positive cases. Thirty-five cases of idiopathic lymphocytic encephalitis were retrieved from the Animal Health Laboratory / Ontario Veterinary College archives. As controls, 32 animals with non-lymphocytic encephalitis and 40 animals with no neurologic disease or encephalitic lesions were selected. All animals were screened using RT-qPCR for bovine astrovirus. No controls tested positive for bovine astrovirus. Four of the 35 animals (11%) with lymphocytic encephalitis tested positive for astrovirus. The four positive cases of astrovirus encephalitis were investigated with immunohistochemistry. The perivascular cuffs and glial nodules were composed overwhelmingly of CD3+ T lymphocytes. To investigate the historic role of bovine astrovirus encephalitis in Ontario cattle, an additional 21 cases from an older archive (1988-1998) were tested for bovine astrovirus, with 7 cases testing positive. In total, 56 cases of lymphocytic encephalitis were tested for astrovirus, and 11 tested positive (19.6 %). For the remaining cases of idiopathic lymphocytic encephalitis, a PCR panel was performed to search for other known causative agents. This included rabies virus, WNV, EEEV, OHV-2, BVDV, BHV-1, Listeria monocytogenes, and Chlamydia species. Nine of these 45 remaining cases (20 %) tested positive for other agents (EEEV, L. monocytogenes, BVDV, BHV-1, and OHV-2), leaving 36 of the initial 56 idiopathic cases of encephalitis (64 %) without a definitive diagnosis. Overall, 19 % of cases of lymphocytic encephalitis without a previously identified cause in Ontario cattle, from 1990-2019, tested positive for bovine astrovirus. This virus is therefore an important causative agent of fatal lymphocytic encephalitis in Ontario.en_US
dc.description.sponsorshipOntario Ministry of Agriculture, Food and Rural Affairs
dc.publisherUniversity of Guelphen
dc.rights.licenseAll items in the Atrium are protected by copyright with all rights reserved unless otherwise indicated.
dc.titleBovine Astrovirus and its Potential Role in Bovine Lymphocytic Encephalitisen_US


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