Introduction
Tsetse flies (Diptera: Glossinidae) are the sole biological vectors of Human African Trypanosomiasis (HAT) and African Animal Trypanosomiasis (AAT) in sub-Saharan Africa. Over 57 million people are at risk of HAT across 36 countries in Africa [1], while AAT significantly impacts livestock production, with an annual economic loss of about $1.5 billion [2]. Tsetse flies, distributed in almost all of sub-Saharan Africa, are obligate blood-sucking Diptera in the family Glossinidae and genus Glossina [3]. This genus comprises 33 species and subspecies, categorized into Fusca (forest), Palpalis (riverine), and Morsitans (savannah) groups based on their habitats.
The Palpalis and Morsitans groups comprise the major vectors of HAT and AAT, respectively. Important vectors within the Morsitans group include Glossina morsitans morsitans, Glossina morsitans submorsitans, Glossina morsitans centralis, Glossina pallidipes, Glossina austeni, and Glossina swynnertoni, while the same within the palpalis group include Glossina fuscipes fuscipes, Glossina fuscipes quanzensis, Glossina palpalis palpalis, Glossina palpalis gambiensis, and Glossina tachinoides [3]. The Glossina palpalis sensu lato and G. tachinoides are the most widespread species in western Africa and Ethiopia, with G. fuscipes sensu lato predominating tsetse fly populations in central Africa and G. morsitans and G. pallidipes in eastern and southern Africa (Figure 1) [3].
Control of tsetse flies constitutes the cornerstone of HAT/AAT suppression in Africa. Information on the genetic structure of tsetse flies can reveal the nature and degree of connectivity or isolation between different populations, which can be exploited in the design of effectively integrated initiatives for control of the flies.
Connected populations typically require a rolling carpet approach, a concerted, simultaneous approach targeting entire populations of tsetse flies within vector control initiatives. Alternative management strategies may also be effective, depending on the context.
In contrast, isolated populations can be eliminated/eradicated with minimal reinvasion risk. Successful eradication efforts have been achieved in Unguja Island in Tanzania (G. austeni) [4], Niayes region in Senegal (G. p. gambiensis) [5], Okavango Delta in northern Botswana (G. m. centralis) [6], Burkina Faso (G. p. gambiensis and G. tachinoides) [7], and Nigeria (G. p. palpalis) [8].
Population genetics helps assess the impact of control efforts by revealing changes in the genetic structure of fly populations. For instance, studies on G. p. gambiensis in Guinea and G. p. palpalis in Ivory Coast found no genetic changes before and after control interventions 9, 10. This suggests potential a posteriori connectivity between tsetse fly populations in controlled and non-controlled areas.
