The mosquito species Aedes scapularis was first observed in larval form in the Florida Keys 75 years ago. A new study by Lawrence Reeves, Ph.D. and colleagues found that Aedes scapularis is now established in mainland Florida in counties Miami-Dade and Broward. (Courtesy photo of Lawrence Reeves, Ph.D.)
By John P. Roche, Ph.D.
Aedes scapularis is a mosquito that can spread yellow fever, the Venezuelan equine encephalitis virus, and other human pathogens. It has a wide range, from Texas to parts of South America and much of the Caribbean. In 1945 three specimens of the larva Ae. scapularis were found in Monroe County, Florida, in the Middle Florida Keys, but Ae. scapularis has not been seen in Florida since – until now. A new study published in November in the Journal of Medical Entomology by Lawrence Reeves, Ph.D., of the University of Florida and colleagues at UF, the Broward Mosquito Control Section, and the Miami-Dade Mosquito Control Division reports that Ae. scapularis is now located in mainland Florida in Counties Broward and Miami-Dade. This has potential public health implications in the region.
The University of Florida study used 121 mosquitoes collected from traps through routine mosquito sampling by mosquito control programs in Miami-Dade and Broward counties, as well as during field sampling in ecological research. The mosquitoes were identified as Ae. scapularis with morphological keys. Members of a subset of specimen mosquitoes were identified by a technique called a DNA barcode.
The researchers compared the cytochrome C oxidase subunit I gene under Ae. scapularis and all related mosquitoes in the US that are members of the so-called Ochlerotatus group: Ae. Condoles, Ae. infirmatus, Ae. the voter, Ae. Tortilis and Ae. trivittatus. Genetic analysis confirmed the morphological identification and confirmed that Ae. scapularis is based in Florida. Little genetic divergence was also noted between sequences from two other species in the Ochlerotatus group: Ae. Condoles and Ae. Tortilis. The researchers then examined another gene (the internal transcribed spacer 2 gene) from several mosquitoes of the Ochlerotatus group agenetically. There was still a small divergence between Ae. Condoles and Ae. Tortilis, suggesting that individuals are identified as Ae. Condoles and Ae. Tortilis can be members of the same species – a finding that is a fascinating by-product of the study.
“The key finding of the manuscript,” says Reeves, “is that Aedes scapularis, an alien mosquito and a potential pathogen, is now established in the southern Florida peninsula.” The Florida Strait was likely a geographic barrier to the species, and now that it has crossed that barrier, Aedes scapularis could potentially spread further north and west to fill any contiguous areas suitable for the environment. “
What is the significance of this finding? One possibility is that Ae. scapularis could transmit disease to people in Florida. “Aedes scapularis has been found to be naturally infected with a number of pathogens in South America and elsewhere,” Reeves says. “It’s hard to say at the moment how Aedes scapularis might be involved in the transmission of this or any other pathogen in Florida, but the species is ecologically well positioned to be a vector because it is easy to human feed: some populations are good Adapted to human-dominated habitats, they feed on a variety of hosts, and they easily feed on humans. “
new study published in November in the Journal of Medical Entomology reported that the mosquito species Aedes scapularis– previously discovered only once in Florida, in 1945 – is now established in mainland Florida in Counties Broward and Miami-Dade. “Of Florida’s 16 established non-native mosquitoes, 13 were first discovered in the state since 1985 and 10 were first discovered since 2000,” says Lawrence Reeves, Ph.D. (Courtesy photo of Lawrence Reeves, Ph.D.)
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Another important aspect of this study is that it could provide insight into how invasive mosquito species enter Florida. This information could help identify routes through which mosquitoes spread and provide insights that could help mosquito control authorities reduce the future establishment of new invasive mosquito species.
This whole study started when Reeves was collecting a female Ae. scapularis in a trap in Florida City in the summer of 2020. “At the time, we didn’t have much to understand how widespread this mosquito was or whether the species was really common in Florida City,” says Reeves Florida. “A subsequent collaboration with the Miami-Dade Mosquito Control Division and the Broward Mosquito Control Section helped Reeves and his colleagues develop a solid picture of the species’ presence.
There are many more research questions that Reeves and his colleagues would like to explore. You are interested to know how far the geographic distribution of Ae goes. scapularis will expand in the future. “We also hope to study the ecology here in the state,” says Reeves, “to get an idea of the visiting associations within the established area.”
The creation of Ae. scapularis and other invasive species are not only geographical but also ecological. “Of Florida’s 16 established non-native mosquitoes, 13 were discovered in the state for the first time since 1985 and 10 were discovered for the first time since 2000,” Reeves says. “To speculate, there is a possibility that recent trends in climate, trade, and / or human movement are encouraging non-native mosquitoes in Florida, and our detection of Aedes scapularis is part of that trend.”
The establishment of invasive species is partly ecological, but the effects of mosquitoes are epidemiological. With more mosquito species, more pathogens could be transmitted to humans, or the dynamics of pathogen transmission could shift for better or worse, making both health care and mosquito control difficult. Future research on Ae. Scapularis and other invasive mosquitoes promise ways to find ways to reduce and contain the incidence of these vectors.
John P. Roche, Ph.D.is an author, biologist, and educator who is dedicated to making rigorous science clear and accessible. Dr. Roche, Director of Science View Productions and Associate Professor at the College of the Holy Cross, has published over 200 articles and written and taught extensively on science. More information can be found at https://authorjohnproche.com/.