Integration of insect sterility and insecticides for control of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) in Tanzania. I. Production of tsetse flies for release

Abstract

A colony of Glossina morsitans morsitans Westw. was established in the laboratory in Tanga, Tanzania. After being expanded to the planned level of 60 000 flies, the stabilised colony was used to support a field trial using surplus males that were sterilised and released. The production system consisted of an adaptation of the in vivo rearing techniques developed at the Tsetse Research Laboratory, England. Goats were hosts for 90 % of the production; the balance was fed on rabbits. Techniques were developed to standardise the pupal off-take from stabilised colonies in each of three separate insectary units. Puparia were collected daily and kept separately until 52% emergence had occurred; these emerging flies, mostly females, were used to replenish the stock colony as needed. Further eclosion was prevented by chilling the remaining puparia (mostly males) quickly at 4°C and then storing at 10 ± 1°C for up to four days prior to irradiation and shipment to the field. About 68 % of the males produced were available for sterilisation. During the 15-month period of production in support of the field experiments, 1 3 million puparia were produced; 0 6 million of these puparia were released at a production cost of $220 per thousand.

Integration of insect sterility and insecticides for control of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) in Tanzania. II. Methods of sterilisation, transportation and release of sterilised males

“…We found that puparial quality could be preserved during cold storage only if the relative humidity was maintained at 70-90%; without humidity control, losses through puparial mortality and adult crippling increased from 17 % after one day of storage to 34 % after five days. The refrigeration process of the incubator caused fluctuations in relative humidity that resulted in these deleterious effects, which were counteracted simply by holding the puparia in a Plexiglas container in which the relative humidity was controlled manually (Williamson et al, 1983a). The deleterious effects on adult quality were even more severe when transport and delivery to release sites were involved.…”

The enhanced suitability of hybrid goats over the indigenous East African goat as hosts for rearing Glossina morsitans morsitans Westwood

“…Techniques adapted for rearing tsetse in Tanzania have been described in detail (Williamson et al, 1983). In general, up to four Geigy 25 cages containing about 25 flies/cage were applied to the clipped flanks of a goat for 15 min, after which they were replaced by subsequent cages.…”

“…Fly-rearing technology that had been developed in Europe was used as a guideline and adapted to African conditions (Williamson et al, 1983). Fly-rearing technology that had been developed in Europe was used as a guideline and adapted to African conditions (Williamson et al, 1983).…”

Integration of insect sterility and insecticides for control of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) in Tanzania. V. The impact of sequential releases of sterilised tsetse flies

“…A strain of G. m. morsitans was collected at Handeni, Tanzania, and colonised at Tanga, where a large-scale production facility was erected (Williamson et al, 1983a). The colony, fed primarily on goats, was increased to a strength of about 60 000 in order to conduct an experimental SIT trial.…”

“…However, as discussed above, the competitiveness of the released sterile flies was normal. The only indication of abnormal behaviour among sterile flies was found in the reduced recovery of adults of the mutant strain ocra of G. m. morsitans which was also bred in the laboratory at Tanga and males of which were released after sterilisation (Williamson et al, 1983a). Although released at a rate of approximately 1:14 with the regular Tanga strain, the ocra males were recovered at a rate of only 1:21, suggesting a reduced fitness in this mutant strain.…”