Metabolites of Metarhizium anisopliae against Malaria Vectors and Non Target Organisms

Neetu Vyas Soam Prakash

doi:10.4172/2161-0983.1000147

Abstract

Vector borne diseases are affecting millions of people annually. Entomopathogenic fungi toxicity on malaria vectors increase mortality rates, and are less effective on nontarget organisms, thus representing a control measure that could be used in integrated programmes. Before metabolites of entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed. In the laboratory, Metarhizium anisopliae were cultured in complete broth media. All instars of Anopheles stephensi and aquatic non-target organisms were passively treated with culture metabolites by different concentrations. The mortality values were subjected by probit analysis for a period of 24, 48 and 72 hours, respectively. Fugal filtrated metabolites significantly increased mortality in the exposed larvae of malaria mosquitoes and had a less adverse effect on nontarget organisms. The highest LC99 (663.77 ppm) values were observed in fourth instars of A. stephensi and found lowest LC99 (254.09 ppm) values in first instars. First instars tolerated applications better than other instars. A positive correlation was found between concentrations of fungal filtrate and percentages mortalities for the all instars of malaria vector. All nontarget organisms were not found susceptible at lower concentrations. Our study marks the first to use of extracellular secondary metabolites of entomopathogenic fungus against all instars of A. stephensi and nontarget organisms. The good biological stability of extracellular metabolites makes this a promising alternative to mycelium and conidial based larvicides. It could be regarded as fungal –based natural larvicides for the use of vector control strategy.

Highlights

Malaria is a vector borne disease of public health concern in tropical and subtropical parts of the world, affecting millions of people annually
The LC values of crude extracellular metabolites of M. anisopliae reported in present study were found effective against all four instar of A. stephensi. 10% mortality was observed just after 24 hours in 1st instar
The LC99 values of M. anisopliae metabolites were higher at 685.84 ppm for the 3rd instar and lowest at 51.286 ppm for the 4th instar (Table 1). on the other hand, adverse effects of cell free culture filtrate of M. anisopliae were observed on selected nontarget organisms at five concentrations after 24, 48, and 72 hours of exposure

Summary

Introduction

Malaria is a vector borne disease of public health concern in tropical and subtropical parts of the world, affecting millions of people annually. The drugs are becoming less effective due to increasing resistance. The most successful method to minimize the incidence of mosquito borne diseases is to eradicate and control the mosquito vectors, which is performed principally by systematic treatment of the breeding places through a combination of environmental management and application [1]. The aquatic part of the mosquito lifecycle consists of an egg stage, four larval stages and a pupae stage. Larval control has a convincing history of malaria eradication and recent studies have shown this approach to be highly effective [2,3,4,5,6,7]. It is worthwhile to investigate the ability of larvicides to control mosquito larvae and the feasibility of their operational use [8]

Methods

Results

Conclusion