Int. J. Environ. Res. Public Health 2010, 7 1. Introduction 1709 Tsetse flies (Diptera: Glossinidae) are found over much of sub-Saharan Africa, in an area approaching 10 million km². The trypanosomes they transmit, after a cyclical development, affect human welfare, both directly through chronic (due to Trypanosoma brucei gambiense) and acute (T. brucei rhodesiense) forms of sleeping sickness (SS, or human African trypanosomiasis, HAT), and indirectly through wasting diseases of livestock (animal African trypanosomiases, AATs). AATs also occur outside Africa, where they have been shown to be transmitted mechanically by other biting flies in Asia, South America, and recently in Europe [1]. It has been estimated that the economic benefits accruing to Africa from the eradication of tsetse could reach US$ 4.5 billion per year [2]. HAT is one of the World Health Organization’s (WHO) defined Neglected Tropical Diseases (see http://www.who.int/neglected_diseases/en/); only a small number of (toxic) drugs can cure HAT. There are few prospects of new drugs being developed, and an increasing problem of drug resistance. Accordingly, the only way that trypanosomiases of both humans and livestock can currently be eliminated is through an integrated strategy combining diagnosis and treatment together with vector control (reviewed in [3]). Recently, the African Union (AU) has launched the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC), a continent- wide initiative that focuses on the progressive elimination in discrete tsetse-infested areas. This vector control program aims to use a variety of methods based on fly species and agro-ecology, including the capacity of local and national tsetse control agencies [4]. Tsetse rely on two major factors for their survival [5]: high local hygrometry and blood from human and mammalian (or reptile) hosts, since both sexes are hematophagous and therefore both can transmit trypanosomes. These tsetse, especially the most dangerous ones of the palpalis group, are intimately related to water (reviewed in [6]). Glossina palpalis gambiensis and G. tachinoides are riverine tsetse species, which disperse mainly along rivers and in forest vegetation, and only very rarely leave this habitat due to their hygrometric needs [7]. Riverine forests comprise their resting and reproductive sites [8,9]. In savannah areas, their survival is conditioned by the availability of ground water, that in turn governs the persistence of forest vegetation [7,10]. Climate change, population growth and economic development that occurred in West Africa during the 20th century had major consequences on human settlements and the landscape. These changes, in turn, have had an impact on the pathogenic systems of human and animal trypanosomiases, as in other vector-borne diseases [11-13]. Since the last century, within West Africa, the foci of SS have shifted from the savannah areas (where SS no longer prevails) to the forest and mangrove areas, but animal trypanosomiases are still present in the savannah areas [14,15]. There has been a dramatic decrease in tsetse of the G. morsitans group (which are usually called savannah tsetse) as a direct result of an increase in human density and its consequences on wildlife, which make up the main blood meal source of this group of tsetse species [10,16]. On the other hand, tsetse species such as G. palpalis (which are called riverine or lacustrine) adapt to high human density and are still found in the largest urban centers in West Africa [17]. Despite the importance of such information, in many African tsetse-infested countries the most widely used tsetse distribution maps were established several decades ago [18]. More recently, the FAO-PAAT Information System identified predicted areas of suitability for tsetse flies in Africa,