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USF researchers find new mosquito-borne diseases

Mosquitoes have long been known to carry diseases such as yellow and dengue fever, but new research has found that they may carry many more – some of which are still unknown.

A study published this month, conducted by researchers from USF, the San Diego State University biology department and the Genome Institute of Singapore, found that a sample of mosquitoes were infected with diseases never before associated with them. Of those diseases, a majority had yet to even be discovered.

USF researcher Mya Breibart, who participated in the study, said the researchers compared the genome sequences found in mosquitoes in San Diego, Calif., to a database of established viruses.

“In our sequences we found insect viruses, human viruses, animal viruses, and then we found a whole lot of completely new viruses that have sequences that are not similar to anything we have (to compare it to),” she said. “It’s a little bit hard to say what these viruses are. As time goes on, people are going to be able to identify more and more of these sequences.”

Breibart said some of the sequences yielded unexpected results, such as DNA sequences matching human papillomavirus (HPV). Though the diseases were present in the mosquitoes, she said follow-up studies must be done to determine whether they are transferable to humans.

“Because we took the mosquitoes and ground them up and then purified the viruses, we don’t really know (which part of) the mosquito was infected,” she said. “If the mosquito landed on a person infected with the papillomavirus, (the virus) could never get into the mosquito and the mosquito could never be a host.”

Though these new viruses are still being studied, one old mosquito-borne disease has made a recent resurgence in Florida.

Last year there were 66 reported cases of dengue fever – a tropical disease that can often lead to death – in the Florida Keys, according to NPR. In 2009, there were 27 cases – the first statewide since 1934.

Warren McDougle, an epidemiology program manager at the Hillsborough County Health Department, said for an outbreak like dengue to spread to the county, a mosquito would have to bite a person with active dengue fever and then bite another person to re-inject it.

The likelihood of a mosquito feeding for a second time is rare, he said.

“(Spreading dengue fever) is a little bit harder than you would think,” he said. “The only reservoirs for dengue fever are humans. Once we find out that a human has tested positive for dengue they are asked to self- isolate until they are no longer able to transmit the disease to a mosquito if bitten by a mosquito here.”

McDougle said mosquito-borne viruses typically feared in Hillsborough County are Eastern Equine encephalitis, West Nile virus and St. Louis encephalitis virus.

Wearing mosquito repellent can help prevent the spread of diseases transmitted from person to person by mosquito, he said.

In the future, Breibart said she would like to sample mosquitoes throughout the country to see what other viruses exist within those regions.

“This opens people’s eyes to how many types of viruses there are out there,” she said. “The field of virology, or actually anything to do with public health, has this problem in which you’re trying to detect viruses because there’s no one test you can do to test for all viruses. Most of the time when you go to the doctor’s they don’t test you for a virus or they test you for specific viruses. You need to have a feel for what’s there before you know what to target.”