Control of Glossina spp (Diptera: Glossinidae) by Pathogenic Organisms and their by Products

Abstract

Tsetse flies Glossina spp (Diptera: Glossinidae) are the dominant vectors of trypanosomes, causative organisms of human African Trypanosomiasis (HAT) and Animal African Trypanosomiasis (AAT) on the African continent. Prior to 1950, destruction of tsetse habitats and wildlife elimination were the main control methods. The advent of chlorinated hydrocarbons led to emphasis on the use of insecticides. Problems of adverse environmental effects on non-target organisms, resistance, etc culminated in an integrated approach. In spite of these efforts, HAT and AAT are still major problems on the continent. Hence the search for new approaches; this period coincided with the emergence of the new discipline of invertebrate pathology. Microbial control agents started to feature in biocontrol of medically important insects. Two eras were discernable: Pre-1960 and Post-1960. There were with two decades, 1939-1959 of reduced activity. In the first era, the emphasis was on field records of pathogenic organisms associated with Glossina from West, Central, East and Southern Africa. Surprisingly, there were no records of viruses or rickettsia. Post-1960, laboratory and field studies intensified with fungi, bacteria, nematodes, viruses and rickettsia. Enhanced knowledge of microbial genetics and cellular physiology led to the paratransgenic strategy of transforming the primary intercellular obligate Wigglesworthia glossinidia and the secondary commensal Sodalis glossinidius symbionts to express gene products that interfere with pathogen transmission. The article concludes with a positive note on the prospects of microbial control of Glossina spp. within an integrated pest management programme.