Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections

Authors: Ramirez, Jose; Schumacher, Molly; OWER, GEOFF - Illinois Natural History Survey; Palmquist, Debra; JULIANO, STEVEN - Illinois State University

Submitted to: PLOS Neglected Tropical Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2021
Publication Date: 11/29/2021
Citation: Ramirez, J.L., Schumacher, M., Ower, G., Palmquist, D.E., Juliano, S.A. 2021. Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections. PLOS Neglected Tropical Diseases. 15(11). Article e0009984. https://doi.org/10.1371/journal.pntd.0009984.
DOI: https://doi.org/10.1371/journal.pntd.0009984

Interpretive Summary: Mosquitoes interact with diverse microorganisms during their lifetime. They have natural bacteria in their guts that help them survive, fungal pathogens trying to kill them and human viral pathogens, which they vector among people. These microbes directly affect the mosquito and indirectly affect each other. A naturally occurring bacterium named Wolbachia is known to limit the ability of an infected mosquito to vector human viruses that cause disease. We showed that while Wolbachia induces the expression of mosquito immune genes, it did not prevent infection by a mosquito killing fungus. We also studied the ability of two fungal pathogens to infect and kill two important mosquito vectors in the USA, with one mosquito showing significant resistance to the lethal action of a fungi. Thus, a mosquito population harboring Wolbachia is still susceptible to control using insect pathogenic fungal biopesticides that provide a more sustainable control option to chemical pesticides.

Technical Abstract: Microbial control of mosquitoes via the use of symbiotic or pathogenic microbes, such as Wolbachia and entomopathogenic fungi, are promising alternatives to synthetic insecticides to tackle the rapid increase in insecticide resistance and vector-borne disease outbreaks. This study evaluated the susceptibility and host responses of two important mosquito vectors, Ae. albopictus and Cx. pipiens, that naturally carry Wolbachia, to infections by entomopathogenic fungi. Our study indicated that while Wolbachia presence did not provide a protective advantage against entomopathogenic fungal infection, it nevertheless influenced the bacterial / fungal load and the expression of select anti-microbial effectors and phenoloxidase cascade genes in mosquitoes. Furthermore, although host responses from Ae. albopictus and Cx. pipiens were mostly similar, we observed contrasting phenotypes with regards to susceptibility and immune responses to fungal entomopathogenic infection in these two mosquitoes. This study provides new insights into the intricate multipartite interaction between the mosquito host, its native symbiont and pathogenic microbes that might be employed to control mosquito populations.