The rate at which the rabies virus evolves in bats may depend heavily upon the ecological traits of its hosts, according to researchers at the University of Georgia (UGA), the U.S. Centers for Disease Control and Prevention and Katholieke Universiteit (KU) Leuven in Belgium. Their study, published May 17, 2012 in PLoS Pathogens, found that the host's geographical location was the most accurate predictor of the viral rate of evolution. Rabies viruses in tropical and sub-tropical bat species evolved nearly four times faster than viral variants in bats in temperate regions. "Species that are widely distributed can have different behaviors in different geographical areas," said Dr. Daniel Streicker, a postdoctoral associate in the UGA Odum School of Ecology and the study's leader. "Bats in the tropics are active year-round, so more rabies virus transmission events occur per year. Viruses in hibernating bats, on the other hand, might lose up to six months' worth of opportunities for transmission." Understanding the relationship between host ecology and viral evolution rates could shed light on the transmission dynamics of other viruses, such as influenza, that occur across regions, infect multiple host species, or whose transmission dynamics are impacted by anthropogenic change. The team's findings could eventually help public health officials better predict when rabies virus transmission could happen in different environments and as environments change, but Dr. Streicker cautions that more research into the rabies virus genome and bats' overwintering ecology is needed. "If viral evolution is faster, it could potentially lead to greater genetic diversity in crucial parts of the viral genome that allow it to shift hosts," he said. "For rabies, we don't yet know what those are, so identifying them will be key.
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