South Florida’s Zika-spreading, dengue-transmitting mosquito population just got a little more crowded.
Two new tropical mosquitoes capable of carrying viruses dangerous to humans have been discovered in Homestead and Florida City by University of Florida researchers. The mosquitoes — native to Central and South America and the Greater Antilles — likely arrived on plants, spread across canals, ditches and ponds in South Florida and will almost surely rise in numbers.
Although they join a growing number of exotic mosquitoes invading the state, researchers were still surprised to find the mosquitoes so far north of their native ranges.
“Nobody had this on their radar,” said UF entomologist Nathan Burkett-Cadena, who inadvertently trapped the mosquitoes while looking for native marsh mosquitoes on an October research trip with assistant Erik Blosser.
“This would speak to some broader environmental changes that have caused Florida to be more accessible and hospitable to tropical mosquitoes,” he said, likely caused by a warming planet.
The discovery of the mosquitoes comes at a particularly bad time for mosquito-weary South Florida. Over the summer and into the fall, a Zika outbreak, the first in the continental United States spread by another invasive mosquito, the Aedes aegypti, hit the hip Wynwood district and Miami Beach, alarming residents and driving away tourists. As of Monday, 243 locally transmitted cases were reported in Miami-Dade County alone, and another 1,048 local and travel cases found statewide, according to the Florida Department of Health. Of those, 209 were pregnant women, whose babies risk being born with brain damage and deformed heads.
Drier, cool weather — and aggressive mosquito control efforts expected to cost about $10 million just in Miami-Dade County — helped control the spread of the container-breeders that feed off humans. But by spring, the mosquitoes, and the disease, will likely return.
The latest invaders, Aedeomyia squamipennis and Culex panocossa, also both carry viruses and can easily spread in populated areas. They lay their eggs on water lettuce, an aggressive aquatic plant that state biologists have dubbed one of the worst invasive weeds. The plants prefer dirty urban water and can be found in thick floating mats in canals and drainage ponds all around the state. But the mosquitoes’ similarities end there, Burkett-Cadena said.
The Aedeomyia mosquito mainly feeds on birds, which spread viruses like West Nile and Eastern equine encephalitis. If enough birds are infected, the viruses can be passed along to humans and other mammals, Burkett-Cadena said. In its native range, the Aedeomyia has transmitted bird malarias like the kind that have wiped out many of the songbirds in Hawaii.
The Culex panocossa, which belongs to the same family of mosquitoes found naturally in Florida, may pose a more urgent threat: it is a confirmed vector for Venezuelan equine encephalitis, which can be lethal to children or the elderly. That also means the mosquito likely carries the local Everglades virus, a member of the same set of diseases and commonly found in native culex mosquitoes.
Because those native mosquitoes don’t do well outside the Everglades and undisturbed wetlands, the virus so far has not been widespread. But Burkett-Cadena worries more cases will now turn up if the mosquito’s tropical cousin begins transmitting it.
“Now you’ve connected these formerly isolated, pristine habitats of transmission with human-dominated habitats,” he said. “What you’re likely to see are more instances of humans being infected with Everglades virus who have not traveled to the Everglades. People in Homestead, in Boca Raton and Fort Lauderdale.”
In its mildest form, the virus causes flu-like symptoms and achy joints, he said. But it can also lead to brain-swelling encephalitis, sometimes triggering comas, although has not been fatal, he said.
The discovery also brings the total number of invasive mosquitoes discovered in Florida over the last decade to nine, a troubling sign that a warming planet is paving the way for more tropical mosquitoes to migrate north, bringing the diseases they carry with them, Burkett-Cadena said.
“The more we look, the more we’re going to find and the more we can expect other formerly tropical mosquitoes to show up and establish in South Florida,” he said.
While removing water lettuce could reduce the spread, he said, stopping them is not likely.
“Our best weapon is information,” he said. Scientists can “identify species most likely to advance so we can prepare ourselves for their arrival and understand the consequences.”
Staff writer Daniel Chang contributed to this report.
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