Scientists Confirm Folk Remedy Repels Mosquitoes

Swatting mosquitoes and dodging other biting bugs is nearly a year-round chore in the Southeast, but such pests are swarming across the country with the advent of summer weather. And with warnings about West Nile virus and other insect-borne diseases out, keeping the pests away has taken on new urgency.

 

American beautyberry, Callicarpa americana. 


A traditional folk remedy, known among people in Mississippi’s hill country for at least a century, may provide some relief without all the worries of DEET and other harsh chemicals. Scientists at the United States Department of Agriculture-Agriculture Research Service housed at the National Center for Natural Products Research at the University of Mississippi have isolated compounds in the American beautyberry plant, Callicarpa americana, that may keep chomping insects away.

Genetically engineered bacteria prevent mosquitoes from transmitting malaria

Researchers at the Johns Hopkins Malaria Research Institute have genetically modified a bacterium commonly found in the mosquito's midgut and found that the parasite that causes malaria in people does not survive in mosquitoes carrying the modified bacterium. The bacterium, Pantoea agglomerans, was modified to secrete proteins toxic to the malaria parasite, but the toxins do not harm the mosquito or humans. According to a study published by PNAS, the modified bacteria were 98 percent effective in reducing the malaria parasite burden in mosquitoes.

"In the past, we worked to genetically modify the mosquito to resist malaria, but genetic modification of bacteria is a simpler approach," said Marcelo Jacobs-Lorena, PhD, senior author of the study and a professor with Johns Hopkins Bloomberg School of Public Health. "The ultimate goal is to completely prevent the mosquito from spreading the malaria parasite to people."

Immune system 'circuitry' that kills malaria in mosquitoes identified

Researchers at the Johns Hopkins Malaria Research Institute have, for the first time, determined the function of a series proteins within the mosquito that transduce a signal that enables the mosquito to fight off infection from the parasite that causes malaria in humans. Together, these proteins are known as immune deficiency (Imd) pathway signal transducing factors, are analogous to an electrical circuit. As each factor is switched on or off it triggers or inhibits the next, finally leading to the launch of an immune response against the malaria parasite. 

The study was published June 7 in the journal PLoS Pathogens.

The latest study builds upon earlier work of the research team, in which they found that silencing one gene of this circuit, Caspar, activated Rel2, an Imd pathway transcription factor of the Anopheles gambiae mosquito. The activation of Rel2 turns on the effectors TEP1, APL1 and FBN9 that kill malaria-causing parasites in the mosquito's gut. More significantly, this study discovered the Imd pathway signal transducing factors and effectors that will mediate a successful reduction of parasite infection at their early ookinete stage, as well as in the later oocyst stage when the levels of infection were similar to those found in nature.

Wolbachia bacteria reduce parasite levels and kill the mosquito that spreads malaria

Wolbachia are bacteria that infect many insects, including mosquitoes. However, Wolbachia do not naturally infect Anopheles mosquitoes, which are the type that spreads malaria to humans.

Researchers at the Johns Hopkins Bloomberg School of Public Health found that artificial infection with different Wolbachia strains can significantly reduce levels of the human malaria parasite, Plasmodium falciparum, in the mosquito, Anopheles gambiae. The investigators also determined that one of the Wolbachia strains rapidly killed the mosquito after it fed on blood. According to the researchers, Wolbachia could potentially be used as part of a strategy to control malaria if stable infections can be established in Anopheles.
Their study is published in the May 19 edition PLoS Pathogens.
"This is the first time anyone has shown that Wolbachia infections can reduce levels of the human malaria parasite (Plasmodium falciparum) in Anopheles mosquitoes," said Jason Rasgon, PhD, senior author of the study and associate professor with the Johns Hopkins Malaria Research Institute and the Bloomberg School's W. Harry Feinstone Department of Molecular Microbiology and Immunology.

Novel anti-viral immune pathway discovered in mosquito

As mosquito-borne viral diseases like West Nile fever, dengue fever, and chikungunya fever spread rapidly around the globe, scientists at Virginia Tech are working to understand the mosquito's immune system and how the viral pathogens that cause these diseases are able to overcome it to be transmitted to human and animal hosts.

In nearly every part of the world, humans and animals experience high levels of morbidity and mortality after being bitten by mosquitoes infected with viruses. More than 100 different viruses transmitted by blood feeding arthropods like mosquitoes have been associated with human or animal disease.
Two especially prolific vectors are the yellow fever mosquito (Aedes aegypti) and Asian tiger mosquito (Aedes albopictus), which is easy to spot because of its striped patterning. Although native to Africa and Asia, these insects can spread through the western world by hitching rides in used tires, which trap water to create a perfect breeding site.