The Genetically Altered Microbes and Viruses in Control of Mosquito-Borne Diseases

Every year, millions of people around the world are affected by mosquito-borne diseases and many die from them. Three mosquito genera— Anopheles , Aedes , and Culex —are the main vectors of human pathogens that transmit malaria, dengue, chikungunya, and lymphatic filariasis. However, the threat of resistance development in the mosquitoes and the parasites is always an issue, forcing scientists over the world to find new ways to prevent transmission of mosquito-borne diseases. Current mosquito control strategies have proved unsuccessful, since no efficient vaccine or drug is available, and there still is a substantial number of morbidity and mortality from these diseases. Concerns related to the use of insecticides for vector control have led to alternative approaches for reducing transmission of mosquito-borne diseases. One area of research involves the use of genetically modified microbes and viruses to meet the anticipated heightened demand for novel management of vector control strategies created by growing human populations and global climate change. Two approaches have particular potential: the disruption of microorganisms required by mosquitoes and manipulation of microorganisms with major impacts on mosquito trait (a) causing pathogenic effects in the host, (b) interfering with the host’s reproduction, (c) reducing the vector’s competence, and (d) interfering with oogenesis and embryogenesis. For genetically altered microbes and viruses to be used in practice, however, requires a better understanding of mosquito microbiota and that symbiotic bacteria and effector molecules be identified. This could prove very useful in mosquito species that are inherently difficult to transform or in sibling species complexes. It is a much more flexible and efficient approach than the use of genetically altered (transgenic) mosquitoes because effector molecules and bacteria can be replaced if they do not achieve the desired result. This technique may therefore become an important integrated pest management tool for mosquito control. Moreover, the prospect of entomopathogenic fungi for the control of vector-borne disease is high because they can be easily cultured and mass produced in the endemic environment. Further, genetic manipulation of mosquito densoviruses (MDVs) is another attractive option for controlling mosquito populations and in turn mosquito transmitted diseases. Genetically modified MDVs with different transgenes reduce the life span of mosquitoes.