Bacterial warfare against mosquito-borne Malaria and Dengue fever

Malaria and Dengue fever are two of the most catastrophic vector-borne infections in the world. In 2010, the Centers for Disease Control estimated the incidence of malaria, which is caused by the parasitic protozoan Plasmodium falciparum, to have reached at least 219 million with 660 thousand fatal cases. The global incidence of dengue fever, caused by an RNA virus in the Flaviviridae family, is also increasing at an alarming rate with current annual estimates of 50 to 100 million cases.

Previous studies have indicated that alteration of the gut flora of Aedes aegypti and Anopheles gambiae mosquitoes can affect their ability to efficiently carry the pathogenic dengue virus and malaria parasite, respectively. Ramirez et al. now show that a Gram-negative soil and water associated Chromobacterium species, termed Csp_P, is able to readily colonize the gut of these mosquitoes. Strikingly, mosquitoes fed with Csp_P -spikedsugar had a significantly shorter lifespan. Remarkably, the authors also show that Csp_P has significant bactericidal activity against the larvae stage of the mosquito lifecycle.

To test the protective affect of Csp_P against P. falciparum or dengue virus infection, mosquitoes were sugar fed the bacterium 2 days prior to being given a blood meal infected with the protozoan or virus. Using oocyst or plaque counting assays, respectively, the authors demonstrated increased resistance of the Csp_P colonized mosquitoes to pathogenic infection by P. falciparum and dengue virus. Csp_P was also found to be a potent trigger of the mosquito immune response and antibacteriocidal against common members of the mosquito gut microflora. Finally, the authors show in vitro exposure of P. falciparum and dengue virus to active Csp_P biofilms causes significant inhibition of parasite development or viral infectivity, respectively.

Taken together, these findings suggest that Csp_P has the potential to be used as a transmission-blocking agent through seeding of baited sugar mosquito traps. Furthermore, the potent larvicidal activity of the bacterium could be developed into a means of controlling mosquito populations in areas rife with malaria and dengue fever. The anti-P. falciparum and dengue virus bactericidal metabolites produced by Csp_P could also be exploited for development of novel therapeutic agents against these devastating diseases in the future.


Original Article: Ramirez, JL. et al. Chromobacterium Csp_P Reduces Malaria and Dengue Infection of Vector Mosquitoes and Has Entomopathogenic and In Vitro Anti-pathogen Activities. PLoS Pathog. 10, e1004398.

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Jennifer Shepherd

A Postdoc with a passion for scientific writing and editing currently working on quality control of translation in bacteria.

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