An experimental biopesticide derived from bacteria is highly effective at killing malaria-carrying mosquitoes, including those that have developed resistance to chemical pesticides, according to initial field tests led by researchers at the Johns Hopkins Bloomberg School of Public Health.
The biopesticide is a powder made from the dead cells of a common soil-dwelling bacterial species. The researchers showed that the biopesticide effectively kills both common mosquitoes and those resistant to chemical pesticides when included in standard baits. Even at sublethal doses, the biopesticide inhibits malaria transmission and makes mosquitoes more vulnerable to standard chemical pesticides. Encouraging findings from initial trials in West Africa suggest that, if successful, larger field trials could one day lead to widespread use of the new biopesticide in malaria-endemic parts of the world.
The study was published online on December 4. Scientific advances.
“This biopesticide has a unique set of characteristics that suggest it could be a powerful new weapon against malaria,” says the study’s senior author, George Dimopoulos, PhD, deputy director of the Johns Hopkins Malaria Research Institute in the Department of Microbiology. and Molecular Immunology at the Bloomberg School. .
Malaria, a parasitic disease transmitted by Anopheles Mosquitoes have long been one of the leading causes of death in the world. According to World Health Organization estimates, around 250 million cases and 600,000 deaths occur each year, mostly children under five years of age in sub-Saharan Africa. Vaccines against malaria have been developed, but they are not widely available or very effective in preventing the disease. While chemical pesticides that kill mosquitoes have been the most effective weapons against malaria to date, insects have developed significant resistance to these compounds. New tools against malaria are urgently needed.
The new biopesticide emerged from a project carried out by Dimopoulos and his team in Panama more than a decade ago. The team captured wild mosquitoes and cataloged bacterial species in their gastrointestinal tracts to see if any could affect the mosquito’s ability to harbor and transmit pathogens. Finally, they found one, a kind of chromobacteriawhich at low doses inhibits the ability of insects to transmit pathogens such as the malaria parasite and dengue virus, and at higher doses kills both adult mosquitoes and larvae. This discovery suggested that the bacteria could be the first biopesticide used against disease-carrying mosquitoes.
To avoid the complications of working with a living organism, the researchers developed a powder preparation made from dead, dried cells of the bacteria. They discovered that the powder retains the mosquitocidal properties of the bacteria and also has a shelf life of years and very high thermal stability. Early tests also found that the biopesticide has no obvious toxic effects on mammalian cells, is easily ingested by mosquitoes when dissolved in standard mosquito baits, and, unlike chemical insecticides, does not lead to the development of genetic resistance in mosquitoes even after ten years. generations of mild exposure.
In the new study, researchers tested the new biopesticide under laboratory conditions and in “MosquitoSphere” facilities (large enclosed spaces with nets that simulate rural and rural environments) in Burkina Faso. The biopesticide killed laboratory strains and wild strains of Anophelesincluding those with resistance to different types of chemical pesticides. Even when the biopesticide didn’t kill the insects, it greatly reversed their resistance to chemical insecticides.
At the highest dose of 200 mg/ml, the biopesticide eliminated the vast majority of mosquitoes at the MosquitoSphere facility, and the researchers’ mathematical modeling suggested it would dramatically reduce local mosquito populations under real-world conditions.
Mosquitoes exposed to the biopesticide, even at low doses, were also severely impaired in their ability to search for a host for a blood meal. In the relatively few insects that managed to ingest blood infected with the malaria parasite in the experiments, the parasites’ ability to infect the mosquito was also drastically reduced. These results suggest that the overall biopesticide could have a very potent effect in reducing malaria transmission.
The researchers’ results so far suggest that the biopesticide works by modifying the activity of a key detoxifying enzyme in mosquitoes, essentially turning the insects’ detoxification systems against them, which would explain why the biopesticide synergizes so strongly with chemical pesticides.
The researchers now plan to seek approval from the US Environmental Protection Agency for the new biopesticide and establish larger-scale field trials to further evaluate its ability to reduce the incidence of malaria.
They also plan more experiments to identify the component or components of the chromobacteria That explains its powerful anti-mosquito effects.
“It was never my intention to focus on biopesticides,” says Dimopoulos, whose primary focus has been mosquito immunity from malaria. “But that’s how these discoveries have worked, and it’s exciting that we’ve identified something novel with the potential to control malaria.”
“Chromobacterium biopesticide overcomes insecticide resistance in malaria vector mosquitoes” was written by Chinmay Tikhe, Sare Issiaka, Yuemei Dong, Mary Kefi, Mihra Tavadia, Etienne Bilgo, Rodrigo Corder, John Marshall, Abdoulaye Diabate and George Dimopoulos .
Funding was provided by the United States Agency for International Development (USAID), the Innovative Consortium for Vector Control, and the Johns Hopkins Malaria Research Institute..