While the current outbreak of Ebola virus in West Africa is very serious, in the current panic people have forgotten that malaria kills thousands of times more people than Ebola each year. In spite of decades of effort, we are still struggling with malaria vaccines, so attention is starting to switch to a new strategy, targeting the mosquitoes that spread malaria.
Just like those of humans, insect guts are full of microbes, and this microbiota can influence the insect’s ability to transmit diseases. A new study reports that a bacterium (Chromobacterium Csp_P) isolated from the gut of an Aedes mosquito can reduce infection of mosquitoes by malaria parasites and dengue virus. The bacterium can also directly inhibit these pathogens in the test tube, and shorten the life span of the mosquitoes that transmit both diseases.
Chromobacterium Csp_P can effectively colonize the midguts of Anopheles gambiae and Aedes aegypti mosquitoes and can, when ingested by the mosquito, significantly reduce the mosquito’s susceptibility to infection with the malaria parasite and dengue virus. We also show that exposure to, and ingestion of, Csp_P can reduce the lifespan of larval and adult mosquitoes. Csp_P has anti-Plasmodium and anti-dengue activity independent of the mosquito, suggesting that the bacterium secretes metabolites that could potentially be exploited to prevent disease transmission or to treat infection.
This comes on top of earlier work involving the use of Wolbachia to attack mosquitoes. We may be some way away from an effective malaria vaccine, but the development of novel control strategies for vector-borne diseases is gaining ground rapidly.
Chromobacterium Csp_P Reduces Malaria and Dengue Infection in Vector Mosquitoes and Has Entomopathogenic and In Vitro Anti-pathogen Activities. (2014) PLoS Pathog 10(10): e1004398. doi: 10.1371/journal.ppat.1004398
Plasmodium and dengue virus, the causative agents of the two most devastating vector-borne diseases, malaria and dengue, are transmitted by the two most important mosquito vectors, Anopheles gambiae and Aedes aegypti, respectively. Insect-bacteria associations have been shown to influence vector competence for human pathogens through multi-faceted actions that include the elicitation of the insect immune system, pathogen sequestration by microbes, and bacteria- produced anti-pathogenic factors. These influences make the mosquito microbiota highly interesting from a disease control perspective. Here we present a bacterium of the genus Chromobacterium (Csp_P), which was isolated from the midgut of field-caught Aedes aegypti. Csp_P can effectively colonize the mosquito midgut when introduced through an artificial nectar meal, and it also inhibits the growth of other members of the midgut microbiota. Csp_P colonization of the midgut tissue activates mosquito immune responses, and Csp_P exposure dramatically reduces the survival of both the larval and adult stages. Ingestion of Csp_P by the mosquito significantly reduces its susceptibility to Plasmodium falciparum and dengue virus infection, thereby compromising the mosquito’s vector competence. This bacterium also exerts in vitro anti-Plasmodium and anti-dengue activities, which appear to be mediated through Csp_P-produced stable bioactive factors with transmission-blocking and therapeutic potential. The anti-pathogen and entomopathogenic properties of Csp_P render it a potential candidate for the development of malaria and dengue control strategies.