Bacterial symbionts in anopheles spp. and other mosquito vectors

Mosquito-borne diseases (malaria, filariasis, dengue, chikungunya, etc.) represent dramatic health problems, mainly in developing countries where these diseases are endemic. Different integrated approaches have been aimed at both vector control and disease control, the most popular represented by the application of DDT and other insecticides. Insecticide-based strategies, integrated with therapeutic and prophylactic treatment of human hosts, has led to eradication of malaria in several regions around the world. However, control strategies based on chemical insecticides are not always practical due to the economic cost, the characteristics of the region, mosquito breeding sites, etc. In addition, the ecological impact of massive insecticide treatment justifies environmental and human health concerns about their application. Alternative, environment-friendly technologies are thus being explored to overcome such constraints. In this context, “biological control” strategies, based on the use of antagonistic organisms/microorganisms, have attracted a great deal of attention. This approach has already been applied to organic culture, forest protection, and the control of some insect vectors of disease (Vu et al., 2005; Kanzok and Jacobs-Lorena, 2007; Thomas and Read, 2007; Toledo et al., 2007). The microbial communities associated with a given mosquito species offer a cornucopia of biological entities that may be useful for the control of the mosquito itself or the diseases it transmits. This horn of plenty has thus far been investigated only for a few mosquito species, and the overall picture of microbial diversity associated with these insects is still far from being completely drawn. Microorganisms associated with mosquitoes might reduce the host fitness or interfere with vector competence, either as “native” microorganisms or after appropriate manipulation. In this regard, a bacterium that is associated with almost all families of insects, including mosquitoes, and that has attracted a great deal of attention is Wolbachia. This bacterial genus and its potential as a weapon against insect pests and vectors has particularly been treated in the first two volumes of Insect Symbiosis (Bourtzis and Miller, 2003, 2006). Here we will focus on other components of the microbial communities associated with mosquitoes, reviewing current knowledge and emphasizing possible applications.