Using hundreds of viral genome sequences, scientists have shown that two major groups of rabies virus have unique evolutionary tendencies. Their findings are presented in a new study published in PLOS Pathogens.

Diseases that jump from other vertebrate hosts to humans are a major public health threat, but the evolutionary mechanisms behind these jumps are poorly understood. With its long history of jumping between host species, the rabies virus offers a good opportunity to identify evolutionary patterns associated with such shifts.

C├ęcile Troupin of Institut Pasteur, Paris, and colleagues compared 321 viral genome sequences collected from 66 countries over 65 years. The analysis revealed very different evolutionary patterns for bat-related rabies, which is found in bats and some carnivores; versus dog-related rabies, which is responsible for almost all human cases of rabies and is found in both dogs and wild carnivores.

The data suggest that different subgroups of bat-related rabies do not evolve uniformly, but dog-related rabies usually evolves at a steady rate. For dog-related rabies, host jumping was linked to multiple evolutionary patterns, such as parallel changes in amino acid sequences between different host species. The data also suggest that dog-related rabies may not need to evolve much to jump to new carnivore hosts.

Looking deeper into dog-related rabies, the scientists found evidence to suggest that, after trade between continents began in the 15th century, dog-related rabies rapidly spread worldwide.

The authors say that the particular combination of species currently infected by dog-related rabies probably arose as a combined effect of historical spread by humans and host jumping.

“The data indicate that different subgroups of bat-related rabies do not evolve uniformly, but dog-related rabies usually evolves at a steady rate,” the authors explain.

“For dog-related rabies, host jumping was linked to multiple evolutionary patterns, such as parallel changes in amino acid sequences between different host species, suggesting that dog-related rabies may not need to evolve much to jump to new carnivore hosts.”

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