The Biology Department is responsible for a wide range of activities including mosquito surveillance, species identification, resistance testing, the sentinel chicken program, the mosquito fish program, and public education and outreach. Many people are unaware of what goes on behind the scenes at mosquito control. All activities conducted by the biology department are a very necessary part of any mosquito control program.
Mosquito surveillance is done in a couple of ways. The most common forms of surveillance are done by trapping and landing rate counts. According to Florida Statute (FS 5E-13), a certain threshold of mosquitoes must be met or exceeded before spraying can occur. As a result, there is no set spraying schedule. Areas are scheduled for spray based on the results of our surveillance methods.
Trapping is primarily done using CDC-light traps which are unbaited. Mosquitoes are simply attracted to a light and get sucked into a net by a fan. The traps are set bi-weekly and collected the following day. The trapped mosquitoes are then brought back to the lab and frozen, where they will then be sorted, identified, and logged. Charlotte County has logged at least 40 different species of mosquitoes! Each species has special characteristics including breeding site preferences and disease vectoring capabilities (or lack thereof). Therfore knowing what species are in the county is extremely important.
Landing rate counts are done in the morning at set locations around the county. A specialist will stand at these locations for one minute and count how many mosquitoes land on them from the waist down. This form of surveillance gives us a quick idea of what the mosquito population is like in each area.
It is important to be able to tell which species are present in an area for a number of reasons. First, only certain species are capable of vectoring specific diseases. For example, an
Aedes aegypti mosquito has the potential to transmit dengue, yellow fever, chikungunya and zika virus. An
Anopheles crucians can potentially transmit malaria. A
Psorophora columbiae is not known to transmit any diseases. Each example of mosquito varies greatly not only by genus and habitat preference, but also by vectoring capabilities, so it is important to know which type are prevalent and how dangerous they can potentially become if a local epidemic were to ever occur.
A second reason for the importance of species identification is that all mosquitoes differ in where they prefer to breed. When citizens lodge a mosquito complaint, the first thing we usually do is go to the address to investigate. If we find an
Aedes taeniorhynchus, we know that that particular mosquito is a salt marsh mosquito, a strong flyer, and most likely came from areas of salt or brackish waters. However, if we find an Aedes aegypti species, we know that these are solely container breeding mosquitoes that are not known to travel far from where they have hatched. With a little detective work the source can usually be found and eliminated, thus eliminating the mosquito issue a resident is experiencing.
A third reason is for record-keeping purposes. It is important from a biological standpoint to have an established history of what species occur and where they are occurring. It is not uncommon for new species to show up and for other species to become less prevalent than in years past. This may be due to changing climate, weather patterns, or even accidental introduction (for example, the introduction of
Aedes albopictus via imported tires from Asia). And there's always the slight possibility of a brand new species being discovered, the hope that nearly every entemologist shares.
Resistance testing is an important way of being able to tell if the mosquito population is still susceptible to the chemical being used. If the same chemical is used over and over, mosquitoes will eventually become naturally resistant to the active ingedient and it will no longer be effective in killing them.
A simple quick test, called cage-testing, can be used by collecting live adult mosquitoes from the wild and putting them inside a small screened cage. This cage is set in an area to be sprayed and collected a short time after the truck or helicopter has passed by. If the spray was effective, most of the mosquitoes inside the cage should have succombed. This test is easy, but isn't always reliable, as other factors could play a role in the mosquitoes' mortality.
A more reliable test that can be done are bottle bioassays. Mosquitoes can be lab-reared from wild larvae or collected in the feild as flying adults. A very dilute formulation of the chemical is made and the insides of the bottles are coated with it, except for one bottle that serves as a control. Adult mosquitoes are then placed in each bottle where they come into contact with the chemical. 100% mortality should be achieved within 30 minutes, except for the control bottle where the mosquitoes are expected to still be thriving. This lets biologists know if the chemical being used is effective against the species being tested.
Mosquito Fish Program
Charlotte County has been providing Gambusia holbrooki (mosquito fish) free of charge to citizens for over a decade. We keep 3 large tanks stocked with these minnows for the purpose of distribution to anyone with ornamental ponds, rain barrels, or other areas that hold water for long periods of time. Mosquito Control personnel have even used them as part of a biological control effort, releasing them into flooded woods, ditches, and even abandonded swimming pools! Related to a guppy, they are surface feeders and are very efficient at eating mosquito larvae and pupae that hang at the surface of the water to breath. These fish are native to Florida and can be seen in abundance in ditches and along pond margins. They stay relatively small, with females only reaching 2-3" in length, and rapidly reproduce. If you are interested in getting some mosquito fish for your ornamental pond, please call the mosquito control hotline at 941.764.4370. The biological specialist will first have to inspect the area where they are to be released before bringing them out.
Sentinel Chicken Program
Charlotte County currently has 7 sentinel chicken flocks placed around the county and these chickens are tested weekly for the presence of West Nile Virus, Eastern Equine Encephalitis, and St. Louis Encephalitis. A small blood sample is taken from the wing and then prepped in the lab and shipped off to the Department of Health Virology Laboratory in Tampa where the serum testing is performed. If any of the sentinel chickens test positive, Mosquito Control responds by spraying the corresponding area to ensure none of these diseases are passed on to humans or horses. Click
here to learn more about the sentinel chicken program!
Mosquito Control provides all types of public outreach free of charge! This includes school assemblies/presentations, tours of the lab to small school groups, display set-ups at public events, and educational talks presented to various civic groups, neighborhood watch organizations, and town meetings. Public outreach is important because citizens and students can play a huge role in eliminating mosquito breeding sites around the home. By educating people on where mosquitoes like to breed, how different species differ in their egg laying and host preferences, and basic mosquito biology in general, people have a much better understanding of what they can do to help and why we do what we do here at mosquito control. If you would like a presentation from us, please call our hotline at 941.764.4370 and leave a message with your contact information and the nature of your call.
NEW!! We are pleased to announce our new mosquito mascot, Abby Albopictus (pronounced al-bo-pik-tus). She is named after one of our common container breeding mosquitoes, Aedes albopictus. Her first unveiling was at the 2016 Charlotte Harbor Nature Festival event and she was a huge hit with kids and adults alike who wanted a photo opportunity with her! We plan to bring Abby along to all future events, school assemblies, and public outreach venues to help spread the important message to Drain, Dress, and Defend!