The discovery that tsetse flies are the vectors of African trypanosomosis, causing sleeping sickness
in man and nagana in cattle, occurred at the start of a rapidly expanding colonialism in sub-Saharan
Africa. Hence, the first research on the fly was largely taxonomic, coupled with a painstaking ecological
approach to determine the identities and distribution limits of the different species.
This was followed by closer attention to the physiology of the fly, both from the academic standpoint
as related to its survival and reproduction in the field, and from the standpoint of its vectorial capacity.
There are still conflicting hypotheses concerning the maturation of trypanosomes within the fly.
Increasing concern for the environment led to a ban in the developed nations on the use of DDT as
an insecticide which had been used successfully for tsetse control in Africa. This was followed by a
ban on the use of organochlorine insecticides in general, and no doubt the next restrictions will be
on the use of organophosphates and upon synthetic pyrethroids which have already been banned
in the UK for the control of houseflies.
Fortunately, research on the role of olfactory and visual stimuli of the tsetse, in the location of potential
hosts, led to an improvement in methods for monitoring fly populations by means of traps and targets
upon which the flies alight. So successful are such devices that, when treated with an insecticide, they
can be used to sustain an increase in natural mortality in fly populations to such an extent that these
populations decline to manageable levels. The techniques constitute an appropriate technology for
the countries of Africa, and attention is now focused on replacing conventional insecticides with more
environmentally acceptable compounds whose development is based on a sound knowledge of the
physiology of the insect.
Perhaps the next major step will be to understand the physiological basis of the acquisition and maturation
of trypanosome infections in tsetse. Modern genetic techniques may then permit the engineering
of flies which cannot transmit trypanosomosis and are therefore reduced to the level of nuisance flies.
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