Vectorial Capacity of Aedes aegypti for Dengue Virus Type 2 Is Reduced with Co-infection of Metarhizium anisopliae

Abstract

Background Aedes aegypti, is the major dengue vector and a worldwide public health threat combated basically by chemical insecticides. In this study, the vectorial competence of Ae. aegypti co-infected with a mildly virulent Metarhizium anisopliae and fed with blood infected with the DENV-2 virus, was examined.Methodology/Principal FindingsThe study encompassed three bioassays (B). In B1 the median lethal time (LT50) of Ae. aegypti exposed to M. anisopliae was determined in four treatments: co-infected (CI), single-fungus infection (SF), single-virus infection (SV) and control (C). In B2, the mortality and viral infection rate in midgut and in head were registered in fifty females of CI and in SV. In B3, the same treatments as in B1 but with females separated individually were tested to evaluate the effect on fecundity and gonotrophic cycle length. Survival in CI and SF females was 70% shorter than the one of those in SV and control. Overall viral infection rate in CI and SV were 76 and 84% but the mortality at day six post-infection was 78% (54% infected) and 6% respectively. Survivors with virus in head at day seven post-infection were 12 and 64% in both CI and SV mosquitoes. Fecundity and gonotrophic cycle length were reduced in 52 and 40% in CI compared to the ones in control.Conclusion/SignificanceFungus-induced mortality for the CI group was 78%. Of the survivors, 12% (6/50) could potentially transmit DENV-2, as opposed to 64% (32/50) of the SV group, meaning a 5-fold reduction in the number of infective mosquitoes. This is the first report on a fungus that reduces the vectorial capacity of Ae. aegypti infected with the DENV-2 virus.

Autodissemination ofMetarhizium anisopliaeandBeauveria bassianainMusca domesticaL. Results in Less Oviposition and Short Gonotrophic Cycle

“…The latter concept perhaps explains the shortened oviposition of M. domestica in our study. The diminution of the gonotrophic cycle time as sublethal influence exerted by both fungi already exists in literature; recently, we demonstrated the gonotrophic cycle was shorter (from 5 to 3 days) in dengue viral/ M. anisopliae-infected A. aegypti females than in single virus-infected ones (Garza-Hernandez et al 2013).…”

A Neuron-Specific Antiviral Mechanism Prevents Lethal Flaviviral Infection of Mosquitoes

“…The head of mosquitoes, where the central neural system locates, can maintain productive flavivirus infection [ 4 ]. Unlike human infection, which can cause severe neurological sequelae, flaviviral infection of the mosquito nervous system intriguingly does not lead to significant malignant pathological consequences, and also does not dramatically influence mosquito behavior or lifespan [ 5 , 6 , 7 , 8 ]. The ability of the neural antiviral mechanisms to control viral replication and to maintain a normal mosquito lifespan may facilitate viral dissemination in nature.…”

Reduced survival and reproductive success generates selection pressure for the dengue mosquito Aedes aegypti to evolve resistance against infection by the microsporidian parasite Vavraia culicis

“…Garza‐Hernandez et al. ). We do, however, expand our discussion concerning the altered blood‐feeding behaviour of females infected with V. culicis as blood‐feeding behaviours strongly influence the epidemiology of vector‐borne diseases (Macdonald ).…”