UF Emerging Pathogens Institute identifies "development" as one of the co-factors contributing to increased mosquito-borne diseases. St. Johns County has allowed "developers" carte blanche to "develop" in and near swamps. County Commission must discuss and debate new development applications in that context. Now. I would be honored to have your vote for a seat on our Anastasia Mosquito Control Commission, Seat 1. From University of Florida Emerging Pathogens Institute:
Florida’s mosquitoes can make you sick: Here’s how to protect yourself
Highlights:
- Florida is home to several mosquito species that can spread potentially life-threatening diseases, including dengue and malaria.
- Climate change, development and global travel can influence the transmission of mosquito-borne diseases in Florida.
- Floridians can manage their risk of these diseases by reducing mosquito habitat around their homes, wearing protective clothing and using insect repellants.
- UF EPI experts are identifying new, effective ways to repel mosquitoes and developing predictive models of Florida’s disease transmission risk.
Mosquitoes aren’t just a nuisance. They can also pass on pathogens through their bites, potentially causing serious illness.
Florida’s subtropical climate and variety of habitat make it a haven for mosquitoes. As a hub for tourism and global travel, the state can act as a petri dish for mosquito-borne diseases, including those from other parts of the world.
Mosquito season runs from March to October in Florida, and mosquitoes are most active when temperatures are in the upper 70s to 90s.
As Florida enters peak mosquito season, experts from the University of Florida’s Emerging Pathogens Institute outline key mosquito species and diseases to know; changes in the state’s disease risk and transmission trends; and the most effective ways to protect yourself.
“Every mosquito bite is a chance to get infected,” said medical geographer Sadie Ryan, an associate professor in UF’s College of Liberal Arts and Sciences and an EPI member. “It’s important to be aware of local disease risks and take preventative measures to protect yourself.”
Four mosquito species that transmit disease in Florida
The vast majority of mosquito species pose no threat to human health, said insect toxicologist Daniel Swale, the EPI Associate Director for Training and Special Projects and an associate professor in UF’s Institute of Food and Agricultural Sciences.
“Most of the mosquitoes we have across the world are actually not blood feeders,” Swale said. “They just feed on nectar or plant materials.”
Four Florida mosquito species, however, are important vectors of human disease and are common around homes throughout the state. They are the yellow fever mosquito, known scientifically as Aedes aegypti; the Asian tiger mosquito, or Aedes albopictus; the southern house mosquito, or Culex quinquefasciatus; and the common malaria mosquito, or Anopheles quadrimaculatus.
Ae. aegypti and Ae. albopictus are daytime biters. Ae. albopictus is more aggressive and most active in the early morning and late afternoon. Cx. quinquefasciatus is primarily active at dawn, dusk and nighttime, though it will also feed during the day. All three species lay their eggs in standing water in pots, abandoned tires, pet dishes, toys, ditches and untreated pools. An. quadrimaculatus bites at dawn, dusk and night, and prefers to breed in freshwater streams, ponds and lakes.
Mosquitoes aren’t the only nuisance biting insects in Florida, said insect toxicologist Jeffrey Bloomquist, a professor in UF’s Institute of Food and Agricultural Sciences and an EPI member. Biting midges, also known as “no-see-ums,” can also be an annoyance, especially in the morning and evening.
Dengue, malaria top list of important mosquito-borne diseases in Florida
Mosquitoes are considered the deadliest animals on the planet, transmitting diseases such as dengue, malaria, chikungunya, yellow fever and Zika.
Because Florida is a global travel hub, Floridians and tourists alike can unwittingly transport pathogens into the state and introduce them to local mosquito populations. The Florida Department of Health actively monitorscases of mosquito-borne diseases in the state, both those acquired abroad and locally. The FDOH also tests Florida mosquitoes for key pathogens, as well as animals such as birds and horses for antibodies that indicate they have recently been infected with a mosquito-borne disease.
Dengue and malaria are particularly important in Florida. The pathogens that cause these potentially lethal illnesses can be spread by local mosquitoes, meaning a person could contract them without travelling outside the state.
In fact, dengue and malaria were common in Florida until the late 1940s, when widespread mosquito control and modern conveniences like air conditioning and screened windows reduced transmission. Without these developments, “Florida would be uninhabitable by most people,” Bloomquist said.
Florida tends to experience small annual outbreaks of dengue, with five locally acquired cases in Miami-Dade and Pasco Counties reported to the FDOH this year so far. Both Ae. aegypti and Ae. albopictus mosquitoes are capable of transmitting the viruses that cause dengue, and cases are most common in South Florida. Ryan said scientists have recently identified two different types of dengue viruses in Florida mosquitoes, raising the possibility of serious illness.
“When you have an infection with one strain of dengue, and then you get a secondary infection with another strain, it’s much more likely to result in severe dengue symptoms,” she said.
If living in or travelling to Florida counties with recent cases of dengue, take extra precautions to protect yourself from mosquito bites. “See your doctor if you experience a sudden, horrific fever and purple rash, and ask if you could have dengue,” Ryan advised.
An. quadrimaculatus can transmit malaria in Florida. In 2023, seven malaria cases in the Sarasota area were the first cases acquired within the state since 2003 and triggered a statewide alert. Though malaria outbreaks tend to be limited, “with Florida being a tourist destination, I don’t think it’s a far stretch to say we’ll see it again,” Swale said.
“Once we relax our prevention, or we get used to living in this land that has been so well manipulated, we tend to forget that malaria is a risk,” Ryan added.
Less common mosquito-borne diseases can still be severe
While very rare in Florida, West Nile virus, St. Louis encephalitis and eastern equine encephalitis are severe illnesses that can spill over from infected animals to people and may cause severe neurological symptoms, Ryan said. Cx. quinquefasciatus can transmit West Nile virus and St. Louis encephalitis from infected birds, and a variety of mosquito species can pick up eastern equine encephalitis virus from birds and infect horses and people. A vaccine for horses is available.
“These diseases may be much rarer in terms of numbers, but they’re very severe, and the symptoms are truly scary,” Ryan said. “For healthcare providers, if people show up with neurological complications of unknown origin, keep in mind that these are possibilities.”
Ae. aegypti can also spread chikungunya, yellow fever and Zika. Florida’s first locally acquired cases of chikungunya were reported in 2014, with no known cases since then. The yellow fever virus is not consistently present in Florida, and transmission of Zika virus has been limited since the 2016 outbreak, said Swale.
How can you protect yourself from mosquitoes?
A simple way of reducing mosquitoes is to limit their access to standing water, which is where they breed.
While mosquitoes abound in Florida’s swamps, marshes and wetlands, they have also made homes for themselves in the state’s most developed areas. Ryan cited a recent study that showed the more urbanized parts of the Miami-Dade area are primarily occupied by Culex and Aedes mosquitoes, both important vectors of disease.
“We’re selecting for mosquitoes that really enjoy the urban environment and can carry on cycling those pathogens with us,” Ryan said. “That also points to potential places for intervention and prevention.”
You can tamp down mosquito numbers by emptying excess water from containers, disposing of spare tires and making sure gutters are clean.
“Dumping out containers, tyke toys, plant pots, kiddie pools and other small areas in the yard that can hold water can really help control a lot of mosquitoes around your residence,” Swale said.
Repellants such as DEET and picaridin can help boost personal protection. DEET is safe, effective and long-lasting, and it remains the universal gold standard of insect repellants, Swale said.
“DEET has been used globally for more than 70 years and is the best repellant we have had on the market since the 1950s,” Swale said. It is highly effective against mosquitoes and also provides some protection against ticks, gnats and biting midges.
Research by Bloomquist and Swale has shown DEET poses few to no health risks when applied as directed. Follow the label instructions, and spray children’s clothing and strollers rather than applying repellants directly to their skin, Swale said.
Repellants derived from natural ingredients such as citronella, lemongrass and vanilla can also be effective for short periods of time.
Clothing treated with synthetic chemicals known as pyrethroids can also ward away nuisance biters, Bloomquist said. Spraying a hat can help protect your head and neck. Do not spray pyrethroids on your skin, Bloomquist cautioned. At peak biting times for mosquitoes, wear long sleeves and tuck pants into socks.
“Everybody hates nuisance biting,” Bloomquist said. “If you protect yourself with repellents, or mosquito protective clothing, you’ll get an extra layer of protection against mosquito-borne diseases.”
Bloomquist has developed a new natural repellant derived from pyrethrins, compounds in chrysanthemum flowers that have been used to control insects for centuries. More effective than DEET, the repellant provides robust protection against mosquitoes and ticks, he said.
“It can go on the market as soon as someone wants to license the patent and develop it,” Bloomquist said.
Climate change could affect Florida’s risk for mosquito-borne diseases
Warming temperatures caused by climate change are allowing mosquitoes to expand their range and lengthen their seasons of activity. But the effects of climate change on mosquitoes and their potential to transmit pathogens are not uniform, and it is not the only factor driving shifts in disease risk, Ryan said.
Changes in land use and the allocation of disease resources and surveillance, particularly in the wake of the COVID-19 pandemic, are also influencing the risk and transmission of mosquito-borne diseases globally.
“There’s not a one-size-fits-all prediction model,” Ryan said. “In a warming world, mosquito-borne diseases will move at different paces, and their seasonality will shift differently.”
The general trend, she said, is that areas at risk for mosquito-borne disease transmission are pushing northwards and southwards with warmer temperatures. Longer mosquito seasons can increase the abundance of mosquitoes, potentially leading to more bites and more incidence of disease. Large-scale weather phenomena such as El Niño can also generate bigger, more severe outbreaks.
According to Ryan’s projection models, Florida is staying warmer longer, increasing hospitable conditions for disease-transmitting mosquitoes where they already thrive and allowing them to move northwards over time.
“In a way, we’re sort of like the natural lab experiment,” Ryan said.
While these shifts could put more strain on health departments and mosquito control efforts, Florida offers a model for how to reactively manage vector-borne disease, she said. When malaria cases cropped up in 2023, the state increased mosquito surveillance and control.
“Other states may not be as prepared as climate change shifts suitability northwards,” Ryan said. “We may see more opportunity for outbreaks that can’t be controlled quickly.”
Also on Ryan’s radar is the rise of a new malaria mosquito, Anopheles stephensi, which has expanded beyond its native range in India and the Middle East and is now as far west as Ghana. It now readily breeds in containers and urban areas, and much of the Americas would be suitable habitat for the species.
“If it shows up in an American port, are we ready for it?” Ryan said.
Written by: Natalie van Hoose
