(Beyond Pesticides, August 25, 2016) The County of Miami-Dade announced Tuesday that it will no longer conduct aerial sprayings on weekdays, to avoid exposing children and teachers. In an effort to control the spread of Zika, the county is consulting with the Centers for Disease Control and Prevention (CDC) and the Florida Department of Health (FDOH), to spray a neighborhood in the county, Wynwood, with Bacillus thuringiensis israelensis (Bti) and Naled. Mosquito officials were conducting the spraying during the early hours of the morning, when fewer people were around, the first day of the school year in Miami-Dade started this week, putting teachers and students at risk of exposure at bus stops.
The county’s move is encouraging, because as research has continuously shown, children and pesticides don’t mix. Studies show children’s developing organs create “early windows of great vulnerability” during which exposure to pesticides can cause great damage. Childhood pesticide exposure has been linked to a range of adverse health endpoints, including cancer, asthma, impaired sexual development, ADHD and other learning disabilities.
“We have adjusted our spraying schedule to avoid any inconvenience to our local school system, and the children, families, and teachers in our community,” the office of Mayor Carlos A. Gimenez said in a statement, “As of this time, no additional adulticide aerial sprayings using naled are planned. We will continue to monitor our mosquito-control surveillance data and will schedule additional sprayings as warranted on weekends.”
Since August 7, the Miami-Dade County Mosquito Control team has conducted seven aerial sprayings in Wynwood, using the larvicide Bti, and the mosquito adulticide, Naled. Bti is a strain of the biological pest control agent, Bacillus thuringiensis (Bt), which is effective against mosquitoes in their larval feeding stages. Thus, Bti is a biological larvicide that prevents mosquitoes from developing into breeding, biting adults, in standing waters that cannot be drained. Bti is proven to be effective and has low levels of toxicity to humans and wildlife. Unlike Naled, Bti will not kill natural mosquito predators, which can take up to a year to replenish and are instrumental in keeping the mosquito population in check over time.
Naled is an organophosphate insecticide with the highest acute toxicity of any mosquitocide. According to the Environmental Protection Agency (EPA), Naled can cause cholinesterase (an enzyme necessary to the transmission of nerve impulses) inhibition in humans, meaning that it can overstimulate the nervous system causing nausea, dizziness, confusion, and at very high exposures (e.g., accidents or major spills), respiratory paralysis and death. Naled and many other commonly used mosquito pesticides, such as permethrin, resmethrin, and malation, are all associated with some measure of human and ecological health risks, especially among people with compromised immune systems, chemically sensitized people, pregnant women, and children with respiratory problems, such as asthma.
Most experts agree that an efficient mosquito management strategy emphasizes public awareness, prevention, and monitoring methods. While mosquitoes may be a nuisance in many areas of the country, that shouldn’t be used as a reason to spray toxic chemicals. When a disease-carrying mosquito that puts human health at risk is present, non-toxic mosquito management strategies should be the first line of defense, however, in extreme cases, even when non-toxic methods are properly applied, disease outbreaks can occur, and communities can be faced with the decision of whether or not to use pesticides. They must determine if they should risk exposing vulnerable populations to potentially harmful diseases caused by mosquitoes, or to chronic or deadly illnesses caused by pesticides.
While there are 175 different species of mosquitoes in the U.S., only a handful of these are vectors for disease. Only adult female mosquitoes bite and require blood meals; males feed on flower nectar. Zika is primarily spread by the bite of an infected Aedes aegypti species mosquito. William Schaffner, MD, an infectious disease expert at Vanderbilt University Medical Center, points out that the Aedes aegypti mosquito is especially hard to combat for multiple reasons. “There’s a history of Aedes being relatively resistant to conventional pesticide,” Dr. Schaffner said. “When we say they’re resistant that means the mosquito inherently can shrug off the pesticide.”
As officials in Miami are working to control Aedes aegypti, the county planned to conduct it’s next spraying of Bti this Saturday, August 27. A Mosquito Control Operations Manager Chalmers Vasquez spoke in Downtown Miami early Wednesday morning, and told 7News Miami, that there are “ten percent less mosquitos in the area since they began preventative measures.” On August 19, Florida Governor Rick Scott announced:
“Today, the Florida Department of Health has confirmed a second location in Miami-Dade County where it is believed active Zika transmission is occurring. This location is a very small area that is less than 1.5 square miles in Miami Beach. While we are adding a second location, DOH is also able to continue reducing the zone in Wynwood. The ability to continue reducing that area where we believe local transmission is occurring shows that our efforts to aggressively spray for mosquitoes and educate the public are working.”
The FDOH is encouraging parents and teachers to continuously educate their children on mosquitoes by launching Spill the Water!, a mosquito bite prevention campaign which encourages students to cover up and spill any source of standing water around their home. FDOH is also suggesting that middle and high school students volunteer, in order to prevent the spread of Zika and other mosquito-borne diseases, by joining/starting student groups that participate in community cleanup efforts. If you live in Florida, and need help identifying high-risk areas in your community, or coordinating a clean-up group, help can be found by contacting your local county health department, local extension office, or mosquito control office. The FDOH can be reached by phone or e-mail at: 850-245-4444 and firstname.lastname@example.org.
Consider contacting Beyond Pesticides for 25 free mosquito doorknob hangers to encourage best management practices in your neighborhood. For more information, Beyond Pesticides’ Mosquito Management program page has a list of resources that can help you and your community safely manage mosquitoes, including least-toxic mosquito repellents, bednets, and proper clothing that can be used to keep mosquitoes safely at bay.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.