Crowds of Crows Spread C. jejuni; Are Humans Vulnerable?

Crows are smart, highly social animals that congregate in flocks of tens of thousands. Such large, highly concentrated populations can easily spread disease -- not only amongst their own species, but quite possibly to humans, either via livestock, or directly. On the campus of the University of California, Davis, during winter, approximately half of the 6,000 American crows that congregated at the study site carried Campylobacter jejuni, which is the leading cause of gastroenteritis in humans in industrialized countries, which could contribute to the spread of disease. The research was published online on June 3, 2016 in Applied and Environmental Microbiology. The open-access article is titled “Influence of Host Ecology and Behvior on Campylobacter jejuni and Environmental Contamination Risk in a Synanthropic Wild Bird.” The investigators posited that the crows' daily wanderings contributed to C. jejuni's spread. To track the crows, they trapped a small number of individuals and attached tiny GPS devices to diminutive backpacks. They affixed these to the birds with harnesses that looped around each wing to attach at the breast. The additional weight represented less than one twentieth that of an average crow. The crows' favored destinations were areas with easy access to food, such as a dairy, barn, and a primate research center. "This movement pattern, coupled with high infection rates, suggests that crows could play an important role in transmission from wild birds to domestic animals and, ultimately, to humans," said first author Conor Taff, Ph.D. Crows' social behavior also probably contributes to the pathogen's spread. Their communal winter roosts can pack thousands of crows into a few trees each night, said Dr.
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