Need to Feed Mosquitoes? Head for the Freezer Aisle
By 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.
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.”
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.
Journal of Insect Science
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.