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Disease States, Other Than West Nile Virus Infection, in American Crows (Corvus brachyrhynchos) Found Dead in Ontario

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Title: Disease States, Other Than West Nile Virus Infection, in American Crows (Corvus brachyrhynchos) Found Dead in Ontario
Author: Dessureault, Fanny
Department: Department of Pathobiology
Program: Pathobiology
Advisor: Barker, Ian K.
Abstract: Following the 1999 North American outbreak of West Nile virus (WNv), the high susceptibility of the American Crow to WNv, the abundance of crows living in close proximity to people, and their use in WNv surveillance, stimulated extensive research on WNv infection in that species. However, little information is available on other causes of disease and mortality in the American Crow. Following a review of the literature on diseases and parasites of the genus Corvus, with emphasis on the American Crow, this research, based on retrospective analysis of 589 dead crows collected in Ontario from 2000 to 2008, and negative for WNv, first defines the characteristics of the study population; then reports infectious and parasitic agents observed; describes the lesions and disease states present in relation to various population parameters; and describes an emerging disease. Gross (584), histologic (565), virologic (184), toxicologic (75) and bacteriologic (376) analyses were performed on the crows in order to define disease states and determine cause of death. Males (51.3%) were more prevalent than females (37.0%; unknown – 11.7%) in the study population, and juveniles were significantly more prevalent in summer. Significantly more adults than juveniles were in poor-to-emaciated body condition. Parasitism, observed in 49.7% of birds, was significantly more frequent in adults than juveniles, and in birds in poor-to-emaciated body condition in comparison to those in good-to-fair body condition. The most common gross diagnoses were trauma (52.6%) and emaciation (13.0%), while moderate splenic lymphoid depletion (21.5%) and microfilaremia (19.1%) were the most frequent histologic findings. The major cause of death was trauma (44.7%), significantly more frequent in juveniles, and observed more commonly in spring and summer. Severe lymphoid depletion and decreased body condition did not predispose to trauma. Infectious and parasitic diseases other than WNv infection are not highly prevalent (11.2%) but they included an emerging disease with winter seasonality, characterized by necrohemorrhagic enteritis, and associated with a reovirus-like agent, which needs further characterization. Starvation killed 3.4%, and toxicity, the most common being Avitrol poisoning, killed 3.2%, while 8.8% were euthanatized. Cause of death was not determined in 28.2% of cases.
Date: 2014-08
Rights: Attribution-NonCommercial-NoDerivs 2.5 Canada
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Attribution-NonCommercial-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 2.5 Canada