Their analysis showed that, depending on the species involved, a single infected bat may infect between 0 and 1.9 members of a different species; and that, on average, CST occurs only once for every 72.8 transmissions within the same species.
"What's really important is that molecular sequence data, an increasingly cheap and available resource, can be used to quantify CST," said Streicker.
Scientist Sonia Altizer of UGA agrees.
"This is a breakthrough," said Altizer. "The team defined, for the first time, a framework for quantifying the rates of CST across a network of host species that could be applied to other wildlife pathogens, and they developed novel methods to do it."
The researchers also looked at the factors that could determine the frequency of CST, using extensive data about each bat species, such as foraging behavior, geographic range and genetics.
"There's a popular idea that because of their potential for rapid evolution, the emergence of these types of viruses is limited more by ecological constraints than by genetic similarity between donor and recipient hosts," said Streicker. "We wanted to see if that was the case."
He found, instead, that rabies viruses are much more likely to jump between closely related bat species than between ones that diverged in the distant past.
Overlapping geographic range was also associated with CST, but to a lesser extent.
"CST and viral establishment do not occur at random, but instead are highly constrained by host-associated barriers," Streicker said. "Contrary to popular belief, rapid evolution of the virus isn't enough to overcome the genetic differences between hosts."
Streicker believes that what he and colleagues have learned about bat rabies will be influential in understanding the ecology, evolution and emergence of many wildlife
|Contact: Cheryl Dybas|
National Science Foundation