Yunnan orbivirus found in Florida for first time

Mosquito, Culex tritaeniorhynchus
Culex tritaeniorhynchus, the mosquito species from which Yunnan orbivirus was first isolated in China. Photograph by Michael Wunderli, available under a creative commons license.

Sixteen years ago, scientists discovered a new kind of orbivirus from a mosquito in Yunnan Province, China. Aptly named the Yunnan orbivirus, it has since also been found in Australia and South America.

A new study by UF researchers, which published in Microbiology Resource Announcements, documents that Yunnan orbivirus is now in North America too, after it was identified in a farmed white-tailed deer in Florida. Orbiviruses mostly infect domesticated and wild ruminants and horses, and while some kinds can infect people, the Yunnan orbivirus is not known to.

Study author John Lednicky, a research professor in the College of Public Health and Health Professions, says the discovery is important because veterinarians could have misdiagnosed past animal illnesses, for lack of knowledge that the virus is circulating in the US.

“Preventive vaccines should probably be used, but are not made available for pathogens not known to be present in an area,” Lednicky says. “Here we have an agent that might have been causing illnesses among our farmed and wild animals that was misdiagnosed all along.”

UF coauthors to the study include researchers from the College of Public Health and Health ProfessionsCollege of Veterinary Medicine, and the Emerging Pathogens Institute.

What they found

Lednicky and his team obtained splenic tissue samples from a deceased farmed white-tailed deer. The animal was observed to be lethargic, salivating excessively, and separated from its herd a few days prior to its death in fall 2019. They then processed the tissue to isolate any viruses that may have been present. Next, they inoculated two different types of cells, a mosquito cell line and a Vero monkey cell line.

Within a few days, cytopathic effects (cellular death) were seen in the mosquito cell culture, but not in the monkey cell culture. The team took additional highly technical and precise steps to identify the virus infecting the cells.

A defining feature of the orbivirus genome is 10 double-stranded RNA segments. Through advanced genetic techniques, the team found complete genetic sequences for all 10 RNA segments. They then analyzed the amino acids and found they were 97.18–99.68% identical to Yunnan orbivirus. A further analysis identified it as a member of the Yunnan orbivirus serotype 1.

What it means

The orbivirus’s 10 RNA segments allow them to essentially mix-and-match genetic material amongst related viruses into new combinations. It’s a process that scientists call reassortment, and it’s this same mixing that drives the emergence of new flu strains annually.

“Now that we know Yunnan orbivirus is in Florida, researchers should be on the lookout for additional emergent orbiviruses, due to the ability of these viruses to reassort and produce new genetic combinations.” Lednicky cautions. “This also raises questions about how this affects our farm production and trade, especially interstate and international transfer of cattle and horses. Are we sending sick animals elsewhere or vice versa?”

Written by: DeLene Beeland