Entomopathogenic Fungi as a Potential Management Tool for the Control of Urban Malaria Vector, Anopheles stephensi (Diptera: Culicidae)

Abstract

Anopheles stephensi (Diptera: Culicidae) is the vector of urban malaria in India and has a significant impact in transmitting infection in cities and towns. Further, WHO has also alarmed its invasive nature as a threat to African countries. Entomopathogenic fungi such as Beauveria bassiana and Metarhizium anisopliae have been found to be highly effective in controlling vector mosquito populations and therefore could be used in integrated vector control programs. Before employing the entomopathogenic fungi into the control programs, an effective isolate must be selected. Two separate experiments were conducted to evaluate the efficacy of Beauveria bassiana (Bb5a and Bb-NBAIR) and Metarhizium anisopliae (Ma4 and Ma-NBAIR) isolates against An. stephensi. Cement and mud panels were treated with fungal conidia with the concentration of 1 × 107 conidia/mL and adult An. stephensi mosquitoes were exposed to the treated panels (24 h after conidia were applied) by conducting WHO cone bioassay tests. The survival of the mosquitoes was monitored daily until the 10th day. In the second experiment, second instar larvae of An. stephensi were treated with fungal (Bb5a, Bb-NBAIR, Ma4 and Ma-NBAIR) conidia and blastospores with the spore concentration of 1 × 107 spores/mL. The survival of larvae was monitored until pupation. All the fungal isolates tested caused mortality in the adult mosquitoes, with varying median survival times. The Bb5a isolate reported lesser median survival times on both cement and mud panels (6 days). The treated mosquitoes showed similar survival rates for each fungal isolate irrespective of the panel type. There was no mortality in the treated larvae; however, a delay in larval development to pupae was observed compared with the untreated control larvae. Ma4-treated larvae took 11 days (95% CI = 10.7–11.2) to become pupae when compared with the untreated control larvae (6 days [95% CI = 5.6–6.3]). The findings of this study will be useful to consider EPF as a tool for the management of vector mosquitoes.

Recent Advancements in Pathogenic Mechanisms, Applications and Strategies for Entomopathogenic Fungi in Mosquito Biocontrol

“…aegypti larvae. Conidia produced on rice grains have demonstrated higher virulence compared to those cultivated on artificial media such as RYA and SDA [12]. Furthermore, the Metarhizium brunneum blastospores exhibit higher virulence toward Ae.…”

“…Entomopathogenic fungi (EPF), on the other hand, can infect mosquitoes through direct contact with the mosquito's cuticle, without the need for ingestion, making them highly attractive as control agents. These fungi are ecologically safe and have the capacity to target mosquitoes at all stages of their life cycle, including adults, eggs, larvae, and pupae [9][10][11][12][13][14]. Additionally, EPF have long-lasting effects on the developmental parameters of mosquitoes, such as reduced fecundity in subsequent generations [15].…”

Biotechnological Potential of Microorganisms for Mosquito Population Control and Reduction in Vector Competence

“…Fungi and their metabolites are potentially useful for the control of medically important mosquitoes [ 135 , 136 , 137 , 138 , 139 , 140 ]. In fact, fungal strains have already been applied as complementary measures for the control of vector mosquitoes [ 141 , 142 , 143 , 144 ].…”

Recombinant Beauveria bassiana expressing Bacillus thuringiensis toxin Cyt1Aa: a promising approach for enhancing Aedes mosquito control

“…B. bassiana is a naturally occurring fungus that can be used as a biological insecticide against mosquitoes ( 9 – 14 ). It has a multistep process to kill mosquitoes ( 15 ).…”