In search of a simple, cost-effective way to maintain laboratory mosquito colonies, biologists at a control district in Florida have turned to food-grade frozen animal blood found at specialty grocery stores. They share the success of their new method for other cash-strapped mosquito-management operations in the open-access Journal of Insect Science. Here, Aedes aegypti mosquitoes in a mesh cage feed on pork blood contained in a petri dish and covered with “plumber’s tape,” placed atop the cage. (Image originally published in Tyler-Julian et al 2021, Journal of Insect Science)

By Andrew Porterfield

Andrew Porterfield

For areas of the United States that have enough mosquitoes to warrant a mosquito control district, it’s often important for those districts to test the effectiveness of insecticides and other products used to manage mosquitoes. For these 700 districts in the U.S., those tests can yield valuable information but are often labor-intensive, expensive, and even stressful.

Testing procedures require control districts to raise populations of laboratory and wild “field” mosquitoes. Raising them requires sources of blood for adult females to produce eggs. But, for most district testing, live chickens are often the source of that blood. Live animals require housing and care for the animals, and they run the risk of introducing animal-borne disease into an insectary. In addition, capturing, restraining and anesthetizing the animal can be stressful and time-consuming for the human tester and (of course) the animal. Artificial blood sources can work, according to a number of studies, but depend on blood feeding devices that can cost up to $3,000.

Kara Tyler-Julian is the field validation biologist at the Lee County (Florida) Mosquito Control District. (Photo courtesy of Kara Tyler-Julian)

In southwestern Florida, the Lee County Mosquito Control District is a little unusual, because it maintains year-round colonies of mosquitoes for testing. (Most districts raise the insects as needed for specific tests.) District biologist Kara Tyler-Julian and her colleagues developed a cheaper, more efficient way to provide blood feeding without the need for live animal hosts. Their study, published last week in the open-access Journal of Insect Science, showed that their modified artificial blood-feeding method could successfully raise mosquitoes. Moreover, their method was created with affordable and easily sourced material, took minimal time and effort to construct and use, and did not require any technical knowledge to assemble.

The district has been using the method for two years to raise four species: Aedes aegypti, Ae. albopictus, Ae. taeniorhynchus, and Culex quinquefasciatus. All four are known vectors of diseases that afflict humans or animals.

Tyler-Julian said she was inspired to find better ways to raise the mosquitoes. When she started working in the district’s laboratory and insectary, “Mosquitoes were being blood-fed using live chickens,” she says. “While this was a successful method, it could be stressful to both the animal and the biologist who needed to capture and restrain the animal.”

After a literature search found no method that could work under the Lee County district’s requirements, one of her colleagues noted that frozen animal blood was often for sale at specialty groceries, for human consumption. Once the blood was found, Tyler-Julian says, “I needed to find an inexpensive, simple and automatic way to keep the blood heated in a way that could work for overnight feeding for difficult wild colonies of Culex that will only feed after working hours.”

In search of a simple, cost-effective way to maintain laboratory mosquito colonies, biologists at a mosquito control district in Florida have turned to food-grade frozen animal blood found at specialty grocery stores. Shown here is preparation of the feeding mechanism used in the lab. Parafilm (left) or PTFE tape (right) is stretched over an aluminum plate forming a pocket on the one side of the plate. Three sides are sealed on the opposite side of the plate. Blood is poured into the open panel, creating a pool on the covered side. The open side is then sealed tightly against the back of the plate. (Image originally published in Tyler-Julian et al 2021, Journal of Insect Science)

Biologists at the Lee County (Florida) Mosquito Control District maintain year-round laboratory colonies of mosquitoes for testing of various management methods. To feed the mosquitoes, they have developed a new, cost-effective feeding method that uses food-grade frozen animal blood found at specialty grocery stores. Here, LCMCD biologist Constance Darrisaw places a feeding plate atop a mosquito cage. (Photo courtesy of Kara Tyler-Julian)

Biologists at the Lee County (Florida) Mosquito Control District capture mosquitoes in the field for laboratory testing of various management methods. (Photo courtesy of Kara Tyler-Julian)

The resulting method consists of store-bought blood, membranes made of parafilm or polytetrafluoroethylene (PTFE) tape (also known as plumber’s tape), and an electric germination mat used by gardeners to sprout indoor seeds. Wild and laboratory colonies of mosquitoes were obtained and raised in the district’s insectary.

In their tests on the new system, the biologists found that wild and laboratory Ae. taeniorhynchus, wild Ae. albopictus, and the laboratory population of Ae. aegypti preferred to feed through the PTFE tape over the parafilm membrane. Lab populations of Ae. albopictus and Cx. quinquefasciatus preferred the parafilm membrane. For blood feeding, both pork and cow blood produced more than 80 percent feeding rates with lab populations of Ae. aegypti and Ae. taeniorhynchus. Lab populations of Ae. albopictus and Cx. quinquefasciatus preferred pork blood.

“Different strains of mosquito will exhibit different feeding rates and difference preferences for blood and membranes,” Tyler-Julian says. “Wild populations do feed at lower rates with this method.”

Despite these variations, the modified feeding method has been successful for the Lee County district, and “is highly accessible for any small-scale mosquito rearing facility with labor or budgetary constraints,” the biologists write.

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He writes frequently about agriculture issues for the Genetic Literacy Project. He is based in Camarillo, California. Follow him on Twitter at @AMPorterfield or visit his Facebook page.