No. 4 (Nov. 1996): OAU: "Eradication Appears Inevitable"
No. 3 (Sep. 1995): Eradication Progress on Zanzibar: Sterile Male Releases Making Big Impact
No. 2 (Dec. 1994): Release of Tsetse Flies from Aircraft Provides Optimal Dispersal of Sterile Insects Even in Inaccessible Areas
No. 1 (Aug. 1994): Belgium, Canada, Sweden, UK, and USA Support Tsetse Fly Eradication Project on Zanzibar
Summary
These Newsletters provide information about an ongoing project in Tanzania that has a Sterile Insect Technique component for tsetse eradication and elimination of the trypanosomosis problem from Zanzibar.
Glossina austeni Newstead is the only tsetse species present on Unguja Island, Zanzibar, Tanzania, and is responsible for the cyclical transmission of animal trypanosomosis. Control efforts between 1986 and 1993 substantially suppressed the G. austeni population by applying pour-on insecticides to cattle and deploying insecticide-treated screens, but this did not result in eradication.
To achieve fly eradication the environmentally friendly SIT was integrated into these activities. At Tanga, a colony of over 700,000 female flies was developed to provide 60,000 sterile males for release weekly. This tsetse colony, the largest in the world, was built up using the latest mass-rearing technology, i.e. in vitro feeding on bovine blood, no sex separation after caging flies immediately after emergence at female:male ratios of 5:1, >200 flies per cage, volumetric estimates of fly numbers, and bulk irradiation of males. Fly quality was assessed routinely by making various observations on the pupae and flies produced.
Gamma-sterilised flies, packed in special paper boxes, were released by aircraft twice a week. In 1995-96 5.5 million sterile males were released. Fly density in the field was monitored with sticky blue/white panels. As the number of released flies increased the male sterile: wild ratio increased until it exceeded 100:1, causing high induced sterility in wild females. In due course no fertile females were captured and the wild fly population declined to an undetectable level. Since early September 1996 no wild flies have been trapped. Blood samples taken recently from sentinel cattle over the whole island showed that, according to the Buffy Coat Technique, the trypanosomosis incidence in cattle averaged less than 0.1%. Tsetse eradication operations are expected to be successfully completed on Zanzibar in 1997.
