Zoonotic viruses certainly got the world's attention with the SARS-CoV-2 pandemic. But viruses have been emerging from animal hosts to infect humans for hundreds of years or longer, and they will continue to pose a threat in the future. Researchers studying the zoonotic virus Zika have now identified Zika virus RNA in African bats in the wild, which is the first time that scientists have identified Zika RNA in any free-ranging bat. The findings were published in Scientific Reports.
This work, noted study leader Anna Fagre, a veterinary postdoctoral fellow at Colorado State University (CSU), has shown that bats are either naturally infected with Zika virus or can be infected by mosquitoes that carry the virus.
"This provides more information about the ecology of flaviviruses and suggests that there is still a lot left to learn surrounding the host range of flaviviruses, like Zika virus," added Fagre. West Nile virus and dengue are some other flaviviruses.
"We knew that flaviviruses were circulating in bats, and we had serological evidence for that," said senior study author Rebekah Kading, an Assistant Professor at CSU. "We wondered: Were bats exposed to the virus or could they have some involvement in [the] transmission of Zika virus?"
To answer these questions, they utilized 198 samples that have been taken from bats in the Zika forest and areas around it in Uganda over the course of several years; some samples were over a decade old. The virus was found in four bats from three species. The pathogen was most closely related to a lineage of Zika found in Asia, which caused an epidemic in the Americas after initial outbreaks in French Polynesia and Micronesia. The Asian lineage Zika virus was found in Angola and Cape Verde in 2016.
"Our positive samples, which are most closely related to the Asian lineage Zika virus, came from bats sampled from 2009 to 2013," said Fagre. "This could mean that the Asian lineage strain of the virus has been present on the African continent longer than we originally thought, or it could mean that there was a fair amount of viral evolution and genomic changes that occurred in African lineage Zika virus that we were not previously aware of."
Because Zika wasn't found in that many bats, Fagre suggested that bats may only be incidental hosts, and not the reservoir, or amplifying hosts. But more work would be needed to know, she added.
"Given that these results are from a single cross-sectional study, it would be risky and premature to draw any conclusions about the ecology and epidemiology of this pathogen, based on our study," she said. "Studies like this only tell one part of the story."
The researchers are planning to continue this work, and use an assay they created that detects a part of the flavivirus genome, and does not rely on PCR amplification.
"There is always a concern about zoonotic viruses," Kading said. "The potential for another outbreak is there and it could go quiet for a while. We know that in the Zika forest, where the virus was first found, the virus is in non-human primates. There are still some questions with that as well. I don't think Zika virus has gone away forever."