GAINESVILLE, Fla. - University of Florida researchers have discovered that a tick common to the southeastern United States may harbor an unusual virus that belongs to the family Arenaviridae. Some arenaviruses are associated with severe hemorrhagic disease and significant mortality in people in South America and sub-Saharan Africa.
Known as Tacaribe virus, the virus discovered in ticks has never before been found in an animal or human species in the United States, report scientists from the UF colleges of Veterinary Medicine and Public Health and Health Professions in a study that appeared in the journal PLOS ONE in December. The researchers found evidence of the virus in nearly 10 percent of ticks collected and they cultured the virus from ticks trapped in North Central Florida.
Although Tacaribe virus is not known to cause human infections, the association that other viruses in the arenavirus family have with human illness, its relative rarity and unknown host in nature intrigue the study's authors.
"This finding is exciting because it expands the range in which these viruses might be circulating in the environment," said Katherine Sayler, who completed her doctoral degree from the UF veterinary college in December and is the study's lead author. "It also raises some really interesting questions about human risk."
One of 29 distinct mammalian viruses that are part of the arenavirus family, Tacaribe virus was last isolated in bats during a rabies surveillance survey conducted in Trinidad in the late 1950s. Only one sample of Tacaribe virus from that survey remains, and molecular testing confirmed that the new tick-derived viral specimen was nearly identical genetically to that remaining sample, the study states.
"We never thought we would find an arenavirus in a tick," Sayler said. "These types of viruses are usually transmitted by rodents."
Although Tacaribe virus had previously been found in bats, recent studies indicate that bats are not the natural reservoir host, and efforts to find the virus in other mammals have failed.
"We still don't know which animal is the natural host of this virus, and whether ticks have harbored the virus for a long time, or if this is something new," Sayler said. "Without knowing if local rodents are a major reservoir of the virus, the extent that Floridians are sickened by the virus, and whether ticks can transmit the virus to humans, it makes it hard for us to know if and when there would be an outbreak. Clearly, much more work must be done."
Sayler, who will continue her work at UF as a postdoctoral associate, said her future research will include searching for more isolates of the virus for genetic comparison.
"We need to use some of the tools that we have at UF to determine if the virus has been around and circulating for a long time, or if it has been absent from Florida and was introduced," she said.
Lone star ticks are found throughout the southeastern United States. Although they are aggressive human biters, they do not transmit Lyme disease, according to the Centers for Disease Control and Prevention. Patients bitten by lone star ticks sometimes develop a circular rash resembling the rash associated with Lyme disease. Lone star ticks can also cause an infectious disease known as ehrlichiosis in people and in pets.
Sayler said that people who are bitten by a tick should try to save the tick for further analysis by a medical professional.
"Health care professionals should also be aware of the potential tick-transmitted pathogens that occur besides the one that causes Lyme disease," Sayler said. "Medical doctors can't be aware of every emerging tropical disease, but if we have greater awareness of emerging diseases, we can move forward from a proactive surveillance effort instead of from a reactive effort, when there is suddenly a huge outbreak and a crisis situation."
Collaborators in the study include Sayler's mentors Anthony Barbet, a professor in the veterinary college's department of infectious diseases and pathology, and John Lednicky, an associate professor in the College of Public Health and Health Professions' department of environmental and global health, along with Dr. William Clapp, a professor of pathology in the UF College of Medicine's department of pathology, immunology and laboratory medicine.
"We would like to thank the UF College of Veterinary Medicine for its support in providing the funding for this study, and for the opportunity I had to work with mentors across departments and colleges, which allowed us to collaborate and to develop a One Health approach to the project," Sayler said.
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