The number of genetic mutations that follow host shifts in rabies virus impacts the speed of disease emergence in new host species, according to new research by ecologists at UGA and the Centers for Disease Control and Prevention. The findings, published in the Proceedings of the National Academy of Sciences, offer the first empirical evidence of the theory that host shifts should happen faster if they involve fewer evolutionary changes.
Many infectious diseases are caused by viruses transmitted from one species to another, posing threats to human, livestock and wildlife health. The impacts of such diseases are magnified when they establish a foothold and persist in new host species. But why some viruses like HIV succeed whereas others disappear after a single outbreak is a major unknown.
Understanding how viruses adapt to new host species is key to answering this question. Daniel Streicker, a postdoctoral associate in the Odum School of Ecology and the study’s lead author, looked at the evolutionary changes in the genome of a virus as it repeatedly jumped into new species.
Streicker studies rabies in New World bats. Because rabies has successfully jumped between so many species, Streicker and his colleagues were able to compare changes to the viral genome across multiple host shifts.
Using virus samples collected from diagnostic laboratories throughout the Americas, the researchers sequenced close to 80 percent of the genome from 30 different strains of rabies virus. They found that mutations were occurring in a gene that hadn’t been well studied but that is important for controlling the speed of viral replication.
Understanding what determines the number of changes needed could eventually inform efforts to anticipate the origins and control the impacts of newly emerging diseases.
The paper’s co-authors are Sonia Altizer, associate dean of the Odum School, and Andrés Velasco-Villa and Charles E. Rupprecht of the CDC.