Date: June 4, 2016
Source: American Society for
Microbiology
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 is
published in Applied and Environmental Microbiology.
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 the crows.
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, PhD.
Crows are also strong flyers, and
able to spread contamination far from the roost.
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 Taff, a postdoctoral
researcher at Cornell University, Ithaca, NY, who conducted some of the
research while he was a postdoctoral fellow at the University of California,
Davis. And crowds of crows, opportunistic omnivores, forage together,
defecating where they eat. "These things together probably explain why
crows have such high prevalence of infection compared to other wild
birds," said Taff.
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