Acta Tropica, 48(1991)159,160 159 Elsevier

ACTROP 00106

Short Communication

Large-scale rearing of Glossina longipennis in the laboratory

S.K. Moloo International Laboratory for Research on Animal Diseases (1LRAD), Nairobi, Kenya

(Received 8 February 1990; accepted 26 March 1990)

Key words: Glossina longipennis; large-scale rearing; Colonization

Glossina longipennis occurs in arid habitats of eastern Africa including Ethiopia, Kenya, Somalia, Uganda, Sudan and Tanzania (Ford and Katondo, 1977; Moloo, 1985). It feeds on a range of vertebrate hosts including man, warthog, giraffe, buffalo, elephant, rhinoceros, dog, cat, hyaena, aardvark and ostrich; but buffalo, elephant and rhinoceros are its favoured hosts (Weitz, 1963). It is a vector of animal trypanoso- miasis and at Nguruman, Kenya, it showed a Trypanosoma congolense infection rate of 4.8% and a T. vivax infection rate of 2.4% (Owaga, 1981). However, very little research has been carried out on G. longipennis compared with other tsetse since it has not been previously colonized. One previous at tempt to rear this tsetse species, using rabbits as hosts, was unsuccessful (Owaga, 1981). The reported reasons for the failure were: unsuccessful mating, high abortion rate and decreased pupal weight with successive generations. The present communication reports the successful large- scale rearing of thisfusca group tsetse species. Its colonization was aimed to provide material to investigate its vector competence for Trypanosoma vivax, T. congolense and T.b. brucei.

In mid-1987, 48 wild females of G. longipennis were caught in Nguruman (1 °50'S/36°05'E), Kenya, and were brought to the I L R A D Tsetse Vector Laboratory. They were kept in a climate controlled room at a temperature of 25_0.5°C with a relative humidity of 80-85%. The tsetse were fed on the ears of lop-eared rabbits daily except at week-ends. A total of 174 pupae, mean weight 79.5_+ 1.8 mg, were produced by these field-caught tsetse. Tsetse which emerged from these pupae formed the parental stock of the colony. The number of mated females in the colony increased and reached the target of 1500 breeding females in December 1988.

The current rearing techniques follow. Adults and pupae are kept in a climate controlled room as above. Pupae are kept in 10 × 40 × 40 cm emergence cages, up to 2000 pupae/cage. The newly emerged tsetse are immobilized at 2-3°C and sexed. The

Correspondence address: Dr. S.K. Moloo, International Laboratory for Research on Animal Diseases (ILRAD), P.O. Box 30709, Nairobi, Kenya.

0001-706X/90/$03.50 ~ 1990 Elsevier Science Publishers B.V. (Biomedical Division)

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sexes are put separately into Geigy cages, 15 per cage. Each cage, 15 x 8.5 x 5 cm, consists of a stainless steel wire frame having a closed end fitted with a corked hole. The cage is covered with black Terylene netting, 4 x 4 mm mesh, which enables the larvae to crawl through into a tray. Teneral females, 15 in each cage, are fed on rabbits' ears and then 16 recently fed 7 to 10-day-old males are introduced into each cage for mating. After about 72 h, the males are removed from each cage using a 35 cm long, 1.5 cm diameter glass tube. The mating period of 72 h is used as after 48 h most tsetse are still mating and even after 72 h, a few pairs are still in copula. These are left to continue mating and may remain so for up to 7 days. The cages of mated females are kept on a rack (Nash et al., 1971). Each rack of ten cages forms a unit of 150 mated females and is given a code number. The flies are offered food for 5 days each week, Monday to Friday. Pupae are also collected from the trays of all the racks on these days, and the number of pupae from each unit code is recorded; pupae from one of the codes units are weighed in bulk. Dead flies are removed on Mondays, Wednesdays and Fridays. Female flies are maintained for 80 days, and on day 81 post-emergence the surviving flies are killed.

In 1989, the mean female stock of the G. longipennis colony was 1579. The insemi- nation rate was ~>99%. The colony produced 30 155 pupae, i.e. 0.37 pupae/female/ week, which is lower compared with that of a colony of related G. brevipalpis (Moloo and Kutuza, 1988). The mean pupal weight was 73.4_+0.3 rag. Mean daily female mortality was 1.5%. Mean survival by day 80 post-emergence was 17.6% in the first half and 31.7% in the second half of 1989. This improvement of the female survival resulted in better fecundity. The emergence rate from the pupae was >~95%. The overall performance was thus good and the colony has provided adequate surplus for research workers at I L R A D and elsewhere.

Acknowledgements

I thank Messrs. S.B. Kutuza, J. Kabata, N. Kuria, M. Owino and A. Kafwa for excellent technical assistance, Mr. S.G.A. Leak for catching tsetse in the field and Miss Elizabeth Muthui for typing the manuscript. I am most grateful to Dr. Ole Mpere, Chief Zoologist in the Kenya Veterinary Services, for his support and access to tsetse areas at Nguruman, Kenya. This is I L R A D Publication No.815.

References

Ford, J. and Katondo, K.M. (1977) Maps of tsetse flies (Glossina) distribution in Africa, 1973, according to sub-generic groups on scale of 1:5 000 000 (plus a set of 9 maps in colour). Bull. Anita. Hlth Prod. Aft. 25, 187 193.

Moloo, S.K. (1985) Distribution of Glossina species in Africa. Acta Trop. 42, 275-28l. Moloo, S.K. and Kutuza, S.B. (1988) Large-scale rearing of Glossina brevipalpis in the laboratory. Med.

Vet. Entomol. 2, 201-202. Nash, T.A.M., Jordan, A.M. and Trewern, M.A. (1971) Mass rearing of tsetse flies (Glossina ssp.): recent

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