Hibernation Allows Rabies Virus to Persist in Bat Population, Colorado State University Study Says

Note to Reporters: A full copy of the paper and a photo of Colleen Webb are available with the news release at http://www.news.colostate.edu.

Rabies persists in the big brown bat population because the virus remains dormant during hibernation, allowing surviving bats to pass it to babies born every June, according to new groundbreaking research from Colorado State University biologists.

The study, called “Host and viral ecology determine bat rabies seasonality and maintenance,” appears this week in the Proceedings of the Academy of Natural Sciences, or PNAS.

The lead author is recent Colorado State graduate Dylan George who worked with Colleen Webb, associate biology professor at CSU, to obtain his doctorate. Other authors include Webb, Richard Bowen, a professor in the university’s Department of Biomedical Sciences, and Thomas O’Shea, a retired scientist for the U.S. Geological Survey.

The research offers the first model – developed in Webb’s laboratory – that explains seasonal peaks in rabies and describes the underlying mechanisms that drive the persistence of rabies in bats. The model combines field and laboratory research, funded by the National Science Foundation, that was conducted by Bowen and O’Shea on the bat population in Fort Collins, Colo.

“Rabies always circulates in the bat population – that’s not true for other diseases that can fade out over time,” Webb said. “Bats can have rabies for a long time before they become infectious and die from it. When these bats are in hibernation and their metabolism is slow, the virus isn’t getting copied – it’s just hanging out. When they wake up, rabies starts progressing again in the individual.”

The disease is then passed along to baby bats when they’re born in mid-June because they’re susceptible to disease, Webb said. Bats are most active from mid-June through September. The prevalence of rabies typically peaks in bats in late summer.

“Disease can wipe through the susceptible part of the population – it really ramps up through the summer and then starts to fall because most young bats have died or gotten over the disease,” Webb said.

Still, less than 1 percent of the bat population appears to have rabies, Webb said.
Unlike other wildlife populations that carry rabies, bats are impossible to vaccinate because they eat insects and wildlife officials can’t sneak the vaccine into their food.

“Together with other collaborators, we are investigating other systems – other bat species and viruses related to rabies – in Europe and Africa to try to understand more generally how bat ecology impacts disease dynamics,” Webb said. “Our work on rabies helps us understand this larger question, which is also very important for public and domestic animal health since bats have been identified as potentially unique disease hosts that appear to harbor a large number of important diseases.”