Tsetse flies are hematophagous flies that are exclusively found in midcontiental Africa, except for 2 species that are found in the Southwestern of Saudi Arabia (Elsen et al., 1990). They are responsible for the transmission of African sleeping sickness (also known as African trypanosomiasis) to human and nagana to livestock (especially cattle). The word tsetse originate form the Tswana language in Southern Africa where it means fly. Tsetse flies regroup flies in the genus Glossina. They resemble to bees in appearance with size ranging from 7 to 13 mm.
Taxonomy and Importance
Tsetse flies are currently classified in the family Glossinidae within the Hippobscoidae (reference). They used to be classified in the Family Muscidae because of their resemblance with stable flies (reference). There is only one genus, Glossina in the family Glossinidae with 23 species. Other authors account the number of species to 31 [reference]. Tsetse flies
can be found in tropical and subtropical regions of sub-Saharan Africa (reference) and in Southwestern Saudi Arabia. Fossil remnants of tsetse flies have been found from the Florissant shale of Colorado in the United States, dating back to 26 millions years ago (reference). They may also occur in certain regions of the world where favorable living conditions are present.
Bio-ecology of Tsetse Flies
Both males and females of tsetse flies are obligatory blood feeders. Female live from 20 to 40 days in general, but geographical variations occurs and life expectancy can reach up to 3 to 4 months. Most tsetse flies prefer to bite their vertebrate host during day time but some species like Glossina medicorum also bite during night time (reference).
Interestingly, male tsetse flies must feed on blood before they are sexually active. Females on the other hand are sexually receptive about 1 days after emergence. Tsetse flies are larviparous, they “give birth” to larvae in contrast to other insects. The fertilized egg hatch in the uterus of the female and give rise to a first instar larva that is maintained in the uterus to accomplish its development. The larvae is fed by milk glands secretion until it reach the third instar at which time the female deposit the larvae on the ground. The life expectancy of tsetse fly is generally 20 to 40 days for females, but variations can occur depending on the environmental conditions and the maximum life span is 3 to 4 months. Males typically live from 2 to 3 weeks (reference).
Tsetse Flies and Disease Transmission
Tsetse flies are vector of trypanosomes (protozoans) that cause African sleeping sickness in humans and nagana in cattle. In 1903, the British Tsetse Fly Commission was the first to associate the African sleeping sickness with trypanosomes. Following the work of this commission, two species of trypanosomes were described according to the part of Africa where the disease occur. Trypanosoma gambiense was identified from The Gambia in West Africa, while Trypanosoma rhodesiense was responsible for the disease in Eastern Africa , especially in Rhodesia (now Zimbabwe). These two disease cause significant mortality and morbidity among people. They also have an impact on the social and economic development of affected people. According to the Center for Disease Control and Prevention (CDC, USA)…… The World Health Organization (WHO) estimate that…. Several species of tsetse flies can vector the disease but the most important one are Glossina morsitans, G. palpalis, G. tachinoides, G. fuscipes, G.pallidipes.
Impact of tsetse fly on the socio economic of people they affect
Tsetse flies have tremendous impact on the economic and social development of the people they affect. The disease they transmit still continue to pose significant mortality and morbidity in Subsaharan Africa. Debilitation caused by African sleeping sickness severely affect people ability to function properly in society. Nagana, the animal form of sleeping sickness severely affect cattle population.
Tsetse Flies Prevention and Control Strategies
Tsetse flies control and prevention rely mostly on the use of insecticides. In the past isolation of infected person and livestock has been use to limit the spread of the disease among healthy individuals. Sterile male technique to affect the fly population dynamics has been contemplated. However just like with any other species there is reluctance to implement this control method.