Discovery of Novel Entomopathogenic Fungi for Mosquito-Borne Disease Control

Abstract

The increased application of chemical control programs has led to the emergence and spread of insecticide resistance in mosquitoes. Novel environmentally safe control strategies are currently needed for the control of disease vectors. The use of entomopathogenic fungi could be a suitable alternative to chemical insecticides. Currently, Beauveria spp. and Metarhizium spp. are the most widely used entomopathogenic fungi for mosquito control, but increasing the arsenal with additional fungi is necessary to mitigate the emergence of resistance. Entomopathogenic fungi are distributed in a wide range of habitats. We have performed a comprehensive screen for candidate mosquitocidal fungi from diverse outdoor environments in Maryland and Puerto Rico. An initial screening of 22 fungi involving exposure of adult Anopheles gambiae to 2-weeks-old fungal cultures identified five potent pathogenic fungi, one of which is unidentified and the remaining four belonging to the three genera Galactomyces sp., Isaria sp. and Mucor sp. These fungi were then screened against Aedes aegypti, revealing Isaria sp. as a potent mosquito killer. The entomopathogenic effects were confirmed through spore-dipping assays. We also probed further into the killing mechanisms of these fungi and investigated whether the mosquitocidal activities were the result of potential toxic fungus-produced metabolites. Preliminary assays involving the exposure of mosquitoes to sterile filtered fungal liquid cultures showed that Galactomyces sp., Isaria sp. and the unidentified isolate 1 were the strongest producers of factors showing lethality against An. gambiae. We have identified five fungi that was pathogenic for An. gambiae and one for Ae. aegypti, among these fungi, four of them (two strains of Galactomyces sp., Mucor sp., and the unidentified isolate 1) have never previously been described as lethal to insects. Further characterization of these entomopathogenic fungi and their metabolites needs to be done to confirm their potential use in biologic control against mosquitoes.

Perspectives of vector management in the control and elimination of vector-borne zoonoses

“…Entomopathogenic fungi are another group of insect pathogens that have been explored as a potential vector biocontrol agent ( Chapman, 1974 ). Fungi of genera Beauveria and Metarhizium have been shown to exert high mortality to medically important mosquitoes of genera Anopheles , Culex and Aedes ( Blanford et al, 2011 ; Accoti et al, 2021 ). The fungal infection exhausts the mosquitoes due to increased metabolic rate and reduces their frequency of taking blood meals.…”

“…stephensi is susceptible to both forms of Metarhizium ( Alkhaibari et al, 2017 ). Notably, it is difficult to culture and mass produce fungi ( Accoti et al, 2021 ). More importantly, these entomopathogenic fungi have been reported to cause symptomatic infections in immuno-compromised humans, raising safety concerns regarding this vector biocontrol agent ( Henke et al, 2002 ; Tucker et al, 2004 ; Lara Oya et al, 2016 ; Goodman et al, 2018 ).…”

Discovery of novel natural products for mosquito control

“…The main drawback is the timing and the need for repeated distribution during the season, and another limitation is that the products available to date are only used for targeting the larval stage of the mosquito life cycle. Natural sources that are currently being explored for the development of new mosquitocidal activities include fungi [16,17], plants [18][19][20][21][22][23][24][25] and microbes [26][27][28][29][30][31], with plants being the most highly represented.…”

The Longevity of Aedes aegypti Larvae in Several Water Sources in Surabaya

“…aegypti mosquitoes are well water sources with the complements such as dark in color, without a lid, unexposed to direct sunlight and without draining during more than a week. 15 In addition, Ae. aegypti larvae are able to live together alongside other microorganisms, such as fungi.…”

“…However, fungi could also be as a lethal pathogen to these larvae and they have been used to control mosquito vectors. 14,15 Surabaya is a DVI endemic area, and has various water sources in various circles of society. Therefore, research is needed on some of these water sources in order to pay attention to their eff ect on the growth of Ae.…”