Host Phylogeny Constrains Cross-Species Emergence and Establishment of Rabies Virus in Bats

Threats to and from Bats Bats appear to be able to host an assortment of alarming pathogens, which, if they do not extirpate the bats, have implications for human health (see the Perspective by Daszak ). For example, exposure to bats is the main source of human rabies in the Americas. But rabies is not generally transmitted among people; humans are a dead end for the virus. Streicker et al. (p. 676 , see the cover) show that rabies virus lineages tend to be specific for bat lineages. It seems that although rabies viruses have the potential for rapid evolution, this property alone is not enough to overcome genetic barriers, which inhibit the onward transmission of rabies virus into a new species. White-nose syndrome, an exotic fungal infection of bats, has, over the past 3 years, spread from upstate New York to West Virginia, killing on average 70% of the animals in a hibernating colony. The infection makes bats restless over winter when they should be dormant, which makes them exhaust their fat reserves, resulting in the death of over a million bats. Frick et al. (p. 679 ) have analyzed population data collected on bats in the northeastern United States for the past 30 years and show that, mainly owing to white-nose syndrome, the once abundant little brown bat is heading for regional extinction in the next 16 years or so. This scale of loss of an insectivorous mammal is expected to have repercussions for ecosystem integrity and for the economic costs of agricultural pest control.