Study shows mosquitoes can spread diseases to manatees

Posted 8/29/20

By Lourdes Rodriguez UF/IFAS ST. LUCIE COUNTY — Mosquito-borne viruses like West Nile and Eastern equine encephalitis pose a threat not only to humans, but also other animals. These viruses have …

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Study shows mosquitoes can spread diseases to manatees

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By Lourdes Rodriguez
UF/IFAS

ST. LUCIE COUNTY — Mosquito-borne viruses like West Nile and Eastern equine encephalitis pose a threat not only to humans, but also other animals. These viruses have caused disease and fatalities in birds, horses and wildlife. Captive orcas have been reportedly killed by mosquito-borne viruses, and there is evidence of infections found in wild Atlantic bottlenose dolphins. Now, Florida’s endangered manatees are the latest to be added to the vulnerable populations list.

Special to the Lake Okeechobee News/UF/IFAS
West Indian manatees prefer shallow, slow-moving waters of rivers, estuaries, saltwater bays, canals and coastal areas.

A new study published in Scientific Report by Lawrence Reeves, an entomologist and research assistant scientist at the Florida Medical Entomology Laboratory of UF/IFAS in Vero Beach, provides the first records of mosquitoes biting West Indian manatees at Everglades National Park.

Reeves’ new research reports observations from the Flamingo Marina at the edge of the Florida Bay in Monroe County that represent the first documented interactions between mosquitoes and any marine mammal in nature. Reeves recorded cases of three mosquito species, Aedes, Anopheles and Culex, interacting with the West Indian manatees. These species are known to carry West Nile virus, Eastern equine encephalitis virus, St. Louis encephalitis virus and Venezuelan equine encephalitis virus.

“The observations show that these mosquitoes can locate and land on manatees at the surface of the water, and they can pierce manatee skin, probing around to find a blood vessel to feed from,” said Reeves. “In doing so, the mosquitoes introduce their saliva into the manatee, which, could infect the manatee with an arbovirus, if that mosquito is itself infected.”

Because mosquitoes only need to bite to infect an organism — not feed — this makes Reeves’ findings an important discovery for a species that is already threatened. West Indian manatees are protected in the United States under the Endangered Species Act and Marine Mammal Protection Act because of their decreasing population.

West Indian manatees prefer shallow, slow-moving waters of rivers, estuaries, saltwater bays, canals and coastal areas. In Florida, wild and captive manatees are frequently observed at the surface of the water, with their dorsal surface or snout exposed to the air for short periods of time, which makes them a target for these mosquitoes that call South Florida home. These behaviors make it easier for the mosquitos to locate and bite the manatees.

Special to the Lake Okeechobee News/UF/IFAS
In Florida, wild and captive manatees are frequently observed at the surface of the water, with their dorsal surface or snout exposed to the air for short periods of time. These behaviors make it easier for the mosquitoes to locate and bite the manatees.

“Until this report came out, we knew that captive orcas in Texas and Florida have become infected by West Nile virus and St. Louis encephalitis virus, and some have died from the diseases,” said Reeves.

Reeves adds that mosquitoes have been observed biting the backs of captive orcas when they float on the surface. Meanwhile, wild Atlantic bottlenose dolphins from the Charleston, S.C., area, and the Indian River Lagoon along the Treasure Coast have tested positive for antibodies to West Nile virus, Eastern equine encephalitis virus, St. Louis encephalitis virus and Venezuelan equine encephalitis.

“This suggests that these mammals have somehow become infected with these viruses,” said Reeves. “We will be working in coastal ecosystems around the Indian River Lagoon over the next year, collecting blood-fed mosquitoes to better understand their host associations.”

ag, manatees, marine, mosquitoes

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