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Declining Mortality in American Crow (Corvus brachyrhynchos) Following Natural West Nile Virus Infection

Reed, Lisa M., Johansson, Michael A., Panella, Nicholas, McLean, Robert, Creekmore, Terry, Puelle, Rose, Komar, Nicholas
Avian diseases 2009 v.53 no.3 pp. 458
Corvus brachyrhynchos, wild birds, bird diseases, West Nile virus, vertebrate viruses, viral diseases of animals and humans, mortality, disease severity, disease prevalence, seroprevalence, Corvus, disease transmission, simulation models, mathematical models, New Jersey
The American crow (Corvus brachyrhynchos) is known to suffer 100% mortality from infection with the New York 1999 strain of West Nile virus (WNV). Following the initial detection of WNV in North America in 1999, we measured prevalence of WNV-reactive antibodies (“seroprevalence”) in free-ranging American and fish crows (Corvus ossifragus) of central New Jersey after each transmission season through 2005. In 2002, seroprevalence in American crow juveniles increased to 14% from the 5% of the previous year, potentially indicating increased survival in this species. Using the annual seroprevalence measurements and the number of human West Nile neuroinvasive disease cases as a surrogate for WNV transmission intensity, we developed a model to estimate the annual WNV-associated mortality rates among both of these crow species. Our model supports the hypothesis that mortality is changing over time; the WNV-associated mortality rate declined over time by 1.5% for American crow and by 1.1% for fish crow. The probability that the trend in mortality was negative was 90% for the American crow and 60% for the fish crow.