Monday, August 8, 2016

Speaker Report: Tsetse Fly: The Scourge of Africa?

In an informative and well-structured talk, Michael Jefferies spoke about the biology, impact on humans and role of the Tsetse Fly in the African ecosystem. His knowledge was gained over a period of six years, from 1961 to 1967 when he worked in Tsetse Fly control in Zambia (then Northern Rhodesia) and Uganda.

Tsetse fly feeding

Tsetse Flies (Order Diptera, genus Glossina) are large biting, blood-sucking flies that inhabit much of mid-con-tinental Africa between the Sahara and the Kalahari Deserts. They look similar to the house fly, except they hold their wings flat on their back. On a map of Africa he showed the distribution of three taxonomically and ecologically distinct groups.

  • Glossina palpalis, the riverine group (Western and Central Africa) 
  •  Glossina fusca, the forest group (West Africa)
  •  Glossina morsitans, the savannah and open woodland group (highlands of East Africa
The problem with Tsetse Fly is that they carry the Trypanosome parasite, which lives in blood and insect hosts. G. palpalis is the chief carrier of the parasite Trypanosoma brucei gambiense, which causes sleeping sickness in humans throughout western and central Africa. G. morsitans is the chief carrier of T. brucei rhodesiense, which causes sleeping sickness in the highlands of eastern Africa. G. morsitans also carries the Trypanosome that causes nagana, a fatal disease of cattle. In 2009 a species of Trypanosome was identified in Koalas, and there are other species in bird and amphibian hosts.

G. morsitans, the species on which Michael worked, is attracted to carbon dioxide. In the 1960s control measures included shooting the host animal, clearing bush, spraying habitat, spraying resting places with residual insecticide, spraying cattle, setting traps with residual insecticide, and the release of sterile males. Breeding males for the latter measure is slow, but as a female fly mates only once in her life, she too is effectively rendered sterile. Once an area has been cleared of Tsetse Fly, it is important to prevent reinfestation. By way of illustration, we were shown a photo of a section of a 300 kilometre long fence, cleared either side, that prevents the movement of game into a Tsetse-free area.

Michael wound up his talk with a series of photos showing Tsetse Fly control in the field, followed by slides of the wildlife he encountered during his time in Africa. Finally he addressed the question: are they the scourge of Africa? In his view probably not, because they live in equilibrium with their food, and by keeping cattle out, preserve land for wildlife.
(Report by Debra Ford)

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