New avian virus discovered in house finches

Although the study of viruses that cause disease in humans has been in the spotlight for the past few years, it is important to better understand how viruses work in other species. In a new study, Arizona State University professors Kevin McGraw and Arvind Varsani investigated the characteristics and infection patterns of a new avian poxvirus in house finches (Haemorhous mexicanus) in Arizona.

This is the first time that the full genome of the house finch poxvirus has been sequenced, and their findings have been published in a recent issue of the journal Transboundary and Emerging Diseases.

It is known that poxvirus infections in animals, including birds, usually cause skin lesions (like chickenpox in humans). However, how the virus works is still not well understood. This study is one of the few that has investigated the molecular and ecological aspects of poxvirus infection in wild birds. 

“This study was aimed more at combining such a phenotypic investigation with a rigorous molecular and genotypic investigation of poxvirus infections in this broadly distributed species of bird,” McGraw said.

The study focused on two main areas. First, researchers wanted to understand which characteristics in the birds could predict poxvirus infection. They examined temporal (day of capture) and biological (including sex, initial body condition and age) aspects, as well as the degree of infection with Isospora spp. protozoan coccidian parasites. Interestingly, none of these were predictors of poxvirus infection.  

“This is unusual, as we've previously found that variables like age, male plumage coloration and glucose levels link to poxvirus infection in these birds,” McGraw said. 

Second, they performed a genetic analysis and phylogenetic comparison (a comparison between genes of poxviruses found in other bird species). DNA was taken from lesions on two male house finches. Using high-throughput sequencing, a precise way to sequence DNA, the viral genome was obtained. It was determined that the sequence was around 354,000 base pairs (A,T,G,C) long. Between the two house finches that were analyzed, there was 99.7% similarity between their genomes, confirming that the same and new finch poxvirus had been sequenced. Lastly, they found that the newly sequenced genome is 82% similar to the canarypox virus genome. Identifying similar poxvirus genes between different bird species is key in understanding their evolution and the relationship between them. 

Figuring out how viruses work in an urban house finch population provides invaluable insights on potential viral threats to wild animals in the light of climate change and habitat loss. The full genome sequences obtained from this study are publicly available at the National Center for Biotechnology Information database’s GenBank under the identifying numbers OM869482 and OM869483.

“Sharing sequence data in a timely manner is essential to address epidemiological questions as well as aiding in the rapid development of diagnostics, therapeutics and prophylaxis to pathogens,” Varsani said. 

McGraw and Varsani are professors in the School of Life Sciences. Varsani is also an associate professor in the Center for Evolution and Medicine and in the Biodesign Center for Fundamental and Applied Microbiomics. This investigation was done in collaboration with other international ecologists and virologists, including Victor Aguiar de Souza Penha, Dean Drake and Simona Kraberger.