Bacterial control of vector-mosquitoes and black flies

Abstract

For centuries man has attempted to control mosquitoes in order to protect himself from mosquito borne diseases and annoyance. The control of mosquitoes using microbial control agents like Bacillus thuringiensis subsp. israelensis (Bti)and Bacillus sphaericus (Bsp) offer man a means to serve all of his interests, protect himself from mosquitoes and protect nature reserves by taking into account the requirements of modern environmental protection. After careful screening, several hundred tons of Bti and Bsp are now used annually world-wide in mosquito control campaigns without evidence of any harmful impact on the environment. This chapter will deal with application histories from various parts of the world, with a specific example from Upper Rhine Valley, Germany. There, Bti and Bsp are applied by KABS (a voluntary mosquito control organisation) using in a combined, mosaic-like integrated biological control strategy. There are considerations of ecological impact as well as close collaboration with the environmental protection authorities. An efficient reduction of more than 90% of the mosquito population was achieved against dominant species like Aedes vexans and Culex pipiens pipiens. Approximately 300 river kilometres and 600 km² inundation areas are treated annually with various formulations of Bti (tablets, wettable powders, water dispersible granules, fluid concentrates, sand granules, ice granules and corn cobs). Bti is also extensively used for mosquito control in the USA when larvicides are required. Examples from China, Thailand and other tropical regions are also described. In these areas, Bti and Bsp are used to control important mosquito vectors including Anopheles sinensis, Aedes albopictus, Aedes aegypti and Culex pipiens quinquefasciatus resulting in a substantial reduction of cases of malaria, lymphatic filariasis and dengue. In the Onchocerciasis Control Programme (OCP) in West Africa, various insecticides are used against the larval stages of black flies (Simulium damnosum s.1.), the vector of Onchocerca volvulus, which is the agent of onchocerciasis. More than 18,000 km in the OCP area are treated regularly. Due to the resistance to chemical insecticides several hundred thousandslitres of Bti are applied annually against black fly larvae. This has resulted resulting in a rapid decrease of the prevalence of this infection among the people protected by the OCP.