The National Institute of Allergy and Infectious Diseases (NIAID) in the United States is supporting the development of products to control mosquitoes without the limitations of traditional chemical pesticides.
On August 20, 1897, the British scientist Sir Ronald Ross dissected a female Anophelesmosquito in his lab in Secunderabad, India, and observed microscopic malaria parasites in the insect’s gut. He went on to prove the role of mosquitoes in transmitting malaria parasites to humans, thus solving one of the great medical mysteries of the day. His landmark discovery is commemorated each August 20 as World Mosquito Day. As Ross wrote in a poem about his feat, “With tears and toiling breath, I find thy cunning seeds, O million-murdering Death.”
Indeed, mosquitoes are the deadliest animals on the planet, transmitting not only malaria parasites but also Zika, West Nile, dengue, and chikungunya viruses as well as other pathogens and bringing death and misery to millions every year. The most common mosquito-control techniques have traditionally involved chemical pesticides that target and kill adult mosquitoes. However, this approach has drawbacks; chemical pesticides may target more than mosquitoes, they may also be toxic to honeybees and other beneficial insects, and may harm fish, aquatic animals, and other wildlife. Additionally, mosquito populations have developed resistance to chemical pesticides over time. These concerns necessitate the development of alternative approaches for mosquito control.
As mosquitoes continue to threaten human health, NIAID is fighting back by supporting basic, translational, and clinical research on non-conventional mosquito-control methods. Through research awards to scientists at universities and small companies, NIAID supports the development of products to control mosquitoes without the limitations of traditional chemical pesticides.
For example, with NIAID support, ISCA Technologies (Riverside, California) is working to develop safer larvicides. One of ISCA’s newest products, SPLAT Bac, controls mosquito populations with no risk to humans or other animals. SPLAT Bac consists of the bacteria Bacillus thuringiensis israelensis, which is toxic only to mosquito larvae, encapsulated in a proprietary waxy substance. This wax matrix contains pheromones (molecules secreted by mosquitoes) that attract female mosquitoes. When SPLAT Bac is applied to a body of water, female mosquitoes are drawn to the area to lay their eggs. After the eggs hatch, the bacteria in SPLAT Bac kill the larvae, halting the next generation of mosquitoes.
MosquitoMate (Lexington, Kentucky) used NIAID support to develop a way to decrease mosquito populations by infecting male mosquitoes with Wolbachiabacteria. Male mosquitoes do not bite, and when Wolbachia-infected males mate with wild female mosquitoes they effectively sterilize them and thwart the development of their offspring. The male-infecting technology has been developed for two species of mosquito—Aedes aegypti and Ae. albopictus—that can spread dengue, Zika, and other viruses. Wolbachia-infected males reduce mosquito populations without chemicals or genetic modification.
NIAID also supported the development of an autocidal gravid ovitrap (AGO) by SpringStar, Inc. (Woodinville, Washington), a device that was initially designed by scientists at the Centers for Disease Control and Prevention. SpringStar’s AGO is a black bucket fitted with a capture chamber and grass-infused water that lures egg-laden female mosquitoes. The females enter the trap through the top screen that is large enough for them to pass through, but small enough to keep birds, squirrels, and other animals out. The mosquitoes try to reach the water to lay their eggs but are blocked by a finer-meshed screen. As they tire, the mosquitoes alight on a replaceable glue board inside the trap and are prevented from laying eggs. This trap is designed to reduce the populations of Aedes aegypti and Ae. albopictus mosquitoes.
Editor’s note: According to the World Health Organization (WHO), nearly half of the world’s population is at risk of malaria. In 2015, there were roughly 212 million malaria cases and an estimated 429 000 malaria deaths. Increased prevention and control measures have led to a 29% reduction in malaria mortality rates globally since 2010.