Last year, an invasive species of mosquito called Aedes scapularis was spotted in Florida for the first time in 75 years. A new paper uses computer modeling of the region’s climate to predict where the blood-sucking insect might spread next.
Researchers from the University of Florida and local mosquito control programs announced that they found an established population of Aedes scapularis in two Florida counties last November, John P. Roach reported for Entomology Today at the time. A follow-up study published in the journal Insects on March 3 shows that the mosquito could eventually spread to at least 16 Florida counties. That has raised concerns because the mosquito is particularly aggressive about biting people, and it can carry several diseases.
University of Florida entomologist Lawrence Reeves tells NPR’s Greg Allen that the same species in Brazil has been found carrying "things like Venezuelan equine encephalitis virus, yellow fever virus and a handful of others."
Identifying a non-native species of mosquito in Florida, where there are already 16 other invasive mosquitoes, begins with mosquito traps that attract the insects with dry ice. Entomologists like Reeves then gather up the hundreds or thousands of bugs from the traps and sort through them with forceps, counting the different species one by one, he tells NPR. Specific coloration of the mosquitoes’ legs helps scientists identify them, and the discovery was confirmed with DNA analysis.
“The central finding of the [first] manuscript,” said Reeves says to Entomology Today in December, “is that Aedes scapularis, a non-native mosquito and potential pathogen vector, is now established in the southern Florida Peninsula. The Florida Strait was likely a geographic barrier for the species, and now that it has crossed that barrier, Aedes scapularis could potentially spread further northward and westward to fill any contiguous areas that are environmentally suitable.”
Reeves adds that climate change, as well as changes in trade and human movement in Florida, may be contributing to the ability of invasive mosquitoes to spread. Aedes scapularis is usually found in Texas, across South and Central America, and in much of the Caribbean. When the species first appeared in Florida in 1945, there were just three larvae found in the Florida Keys and none on the mainland.
Now that the mosquito has been detected with a strong population in two Florida counties, researchers worry that it could spread. The new research uses ecological niche modeling to identify the areas that should be alert to the possibility that Aedes scapularis might show up sometime soon. The paper points to 16 counties around Florida’s coast, as well as southern Alabama, Mississippi and Louisiana.
One of the biggest concerns with the invasive mosquito is the possibility that it could spread disease. Aedes scapularis frequently carry the virus that causes yellow fever, but it’s not yet clear whether it can transmit the virus to humans. But there is real risk because the species thrives in human environments and enjoys the indoors, and because it feeds on many different hosts.
"If you end up with a species that's capable of transmitting to [birds] and likes to also bite humans, that's the prime condition for a spillover event," says study co-author Lindsay Cambell, an entomologist at the University of Florida, to NPR. A spillover event is the name for what happens when a disease passes from a wild animal into humans, which is how scientists believe the Covid-19 pandemic began.
Other species of invasive mosquitoes have caused disease outbreaks in Florida in recent years. In 2013, an outbreak of dengue fever was linked to the presence of Aedes aegypti mosquitoes. In 2016 and 2017, Florida saw cases of the Zika virus, which is spread by the Aedes aegypti and Aedes albopictus mosquitoes. It’s been over a century since a case of yellow fever was recorded in Florida, per NPR.
“This species is not very well established yet, so we have not seen any cases of disease transmission,” says Miami-Dade County Mosquito Control Research Director Chalmers Vasquez to the Miami Herald’s Adriana Brasileiro. “But we will keep an eye on it as we do with other mosquitoes that live here.”