Arthropod vectors  Tsetse flies
Tsetse flies
Author: Dr Reginald De Deken
Licensed under a Creative Commons Attribution license.
DISTRIBUTION
The distribution area of the genus Glossina is restricted to lowland rainforest and wooded savannah
regions of Africa south of the Sahara. Some species were also observed in south-west Saudi-Arabia.
Roughly speaking tsetse flies can be found between the 15th degree of latitude in the Northern
hemisphere and the 30th parallel south (eastern part) or the 20th parallel south (western part). The
distribution is however not uniform but often patchy. Country lying below the 500 mm isohyet does not
support tsetse flies unless there are watercourses with some vegetation along them (forest galleries).
Mountains exceeding 1600 m of height generally form an insuperable obstacle for tsetse flies.
However it is not the altitude itself which plays a role, but rather the low temperatures prevailing at
these heights. Recently, however, G.m.submorsitans has been observed in Ethiopia and Cameroon
at a height of 2000 m, corroborating the hypothesis of global warming of the earth.
The subgenus Morsitans:
It is closely associated with open woodland and wooded savannah with Brachystegia (miombo) or
Colophospermum (mopane) trees in East and Central Africa (e.g. G.m.morsitans and G.pallidipes) or
Isoberlinia (doko) trees in West Africa (e.g. G.m.morsitans). These « savannah tsetse flies» penetrate
during the rainy season in arid areas, while during the dry season they concentrate in denser
vegetation along drainage lines or in better watered woodlands. The flies of the morsitans group are
usually very sensitive to agricultural development, degradation of natural habitats and reduced wildlife
density (especially G.swynnertoni, G.pallidipes and G.longipalpis), although they will feed readily on
domestic livestock when available.
The subgenus Palpalis:
It is found in gallery forests (e.g. G.p.gambiensis and G.tachinoides), near lakes and river systems,
flowing either into the Atlantic Ocean or in the Mediterranean (e.g. G.f.fuscipes and G.p.palpalis), or in
rain forest (e.g. G.p.palpalis, G.calliginea and G.pallicera). The majority of these “riverine” species
need a relatively high atmospheric humidity and shade although G.tachinoides can support great
climatic variations and is found from arid zones in Niger to humid degraded forest in Nigeria. The best
conditions for “palpalis” flies are a temperature of approximately 25°C and an atmospheric humidity of
80 to 85%. These “riverine” tsetse flies cope better with increased human occupation of the land and
environmental changes than the “savannah” flies.
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Arthropod vectors  Tsetse flies
The subgenus Fusca:
All the tsetse flies pertaining to the Fusca group, except for G.longipennis and G.brevipalpis, are
forest flies, including the humid tropical forest. As forest isn’t particularly suited for livestock breeding
their importance as a vector of animal trypanosomosis is generally low. G.longipennis lives in the arid
and semi-arid savannas of East Africa. G.brevipalpis lives in the more humid parts of wooded
savannas of Central, South and East Africa. This species can fly over relatively long distances and
therefore is also observed in open grassland. It has some importance as a vector of animal
trypanosomosis.
Available multimedia
At the website of Program Against African Trypanosomosis (PAAT)
distribution maps of the different Glossina species may be consulted
and downloaded as a pdf or in GIS-format.
http://www.fao.org/Ag/againfo/programmes/en/paat/maps.html
The maps, showing the predicted areas of suitability for the tsetse fly
species, were produced by Environmental Research Group Oxford
(ERGO Ltd) in collaboration with the Trypanosomosis and Land Use
in Africa (TALA) research group at the Department of Zoology,
University of Oxford.
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