Following SARS-COV-2, the Heartland virus – the greatest risk to humans – includes the lone star tick, which has been found in large numbers in Georgia.
This invasive tick, carrying the Heartland virus, was initially discovered in Missouri in 2009, and since then it has spread geographically and from one organism to another.
Scientists from Emory University discovered that the Heartland virus is circulating among lone star ticks in Georgia, confirming active transmission of the virus in the state.
The findings, which include a genetic study of the virus samples isolated from ticks collected in central Georgia, were published in the journal Emerging Infectious Diseases.
The study, led by Yamila Romer with co-author Anne Piantadosi, discovered the Heartland virus in three independent specimen samples of lone star ticks collected in different locations and times, encompassing both the nymph and adult phases of the tick.
The genomes of the three viral samples were found to be comparable to one another, but very different from the genomes of Heartland virus samples from outside the state, according to genetic study.
“These results suggest that the virus may be evolving very rapidly in different geographic locations, or that it may be circulating primarily in isolated areas and not dispersing quickly between those areas,” say the authors.
It was found in 2009 in northwest Missouri after two local men were taken to the hospital with fevers, diarrhea, muscle pains and low white blood cell and platelet counts, all of which were similar to known tick-borne illnesses. This virus was dubbed “Heartland” and later found to be transmitted by Lone Star ticks, which infected the men. Antibodies to the virus were found in blood samples from deer and some other wild mammals after the first study was done.
In the United States, the Centers for Disease Control and Prevention presently recognizes 18 tick-borne diseases, many of which are novel. Lyme disease, which is caused by bacteria and has become the most frequent vector-borne disease in the country in recent decades, is one of the most well-known tick-borne infections.
While Lyme disease can be transmitted by black-legged ticks (commonly known as deer ticks), white-footed mice are a significant source of infection.
When tick larvae feed on the blood of mice and other small mammals and birds that may be carrying the bacterium, they can get infected.
Infected larvae develop into nymphs and adult ticks, which can subsequently infect other animals, such as deer and humans.
While the Lyme disease transmission cycle is widely understood, many issues about how the Heartland virus spreads among different species remain unanswered.
According to the Centers for Disease Control and Prevention, more than 50 instances of Heartland virus have been reported in persons from 11 states in the Midwest and Southeast since it was first discovered in 2009. Many of the instances were serious enough to necessitate hospitalization, and a few people with co-morbidities died as a result. However, because the Heartland virus is still unknown and testing for it are rarely requested, the actual illness burden is thought to be higher.
In Georgia, a single confirmed human infection of the Heartland virus was discovered in a Baldwin County resident who died in 2005 from an unexplained illness, according to a retrospective analysis. The human instance spurred researchers to examine serum samples taken from white-tailed deer in central Georgia in previous years. Deer from that area have been infected with the Heartland virus since at least 2001, according to the findings.
To determine the risk of human disease, the team conducted genomic tests of lone star ticks harboring Heartland virus in central Georgia.
Ticks were gathered from the rural terrain surrounding the Piedmont National Wildlife Refuge by members of the field research team. Team members wore long shirts and long pants tucked into long socks with the tops of the socks fastened with duct tape, even in the scorching Georgia summers. They also used bug spray and performed visual tick inspections on themselves before and after leaving the field to further protect themselves.
Among ticks, the most common in Georgia is the lone star tick, which has a white spot on its back. This tick can be found in wooded areas across the Southeast, Eastern, and Midwest United States. In the nymph stage, they’re about the size of a sesame seed, and as adults, they’re barely a quarter-inch in diameter.
“Lone star ticks are so small that you may not feel them on you or even notice if you’ve been bitten by one,” adds Steph Bellman, a co-author of the study
The team used “flagging” as a way to gather information. A white flannel flag on a pole is swished through the underbrush in a figure-eight motion.
“Every so often, you lay the flag down and use a pair of tweezers to remove any ticks that you find on it and put them into a vial,” explains Bellman.
They collected approximately 10,000 specimens from sites in Georgia’s Putnam and Jones counties, which are both neighboring to Baldwin County, using this labor-intensive method. To test for the presence of the Heartland virus, specimens were divided into groups containing either five adults or 25 nymphs, then crushed and put into a solution.
According to the findings, around one out of every 2,000 specimens obtained from the collecting sites was infected with the Heartland virus. One adult and one nymph sample collected on the same day from a private hunting property in Putnam County proved positive. A second sample of adult ticks from a section of woodlands beside a roadway in Jones County, taken on a later day, also tested positive.
The study’s scope is now being expanded by the researchers. They will collect ticks for testing and conduct spatial studies across Georgia in order to better understand the elements that may increase the risk of Heartland virus.
“We want to start filling in the huge gaps in knowledge of the transmission cycle for Heartland virus,” the team says. “We need to better understand the key actors that transmit the virus and any environmental factors that may help it to persist within different habitats.”
Warmer and shorter winters are a result of climate change, allowing some tick species to spawn more frequently and increase their territories. As more human dwellings encroach on woodland regions and natural habitat is lost, wildlife is forced to reside in denser concentrations, land-use changes are also significantly linked to tick-borne diseases.
“Ticks are both fascinating and terrifying,” Bellman adds. “We don’t have effective ways to control them and they are a vector for many nasty diseases. They represent a large threat to human health that a lot of people may not realize.”
Source: 10.3201/eid2804.211540
Image Credit: Getty
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