Tsetse fly eradicated on the Island of Zanzibar

A four-year campaign on the island of Zanzibar has achieved a historic breakthrough in the battle against the tsetse fly - an insect pest that causes hundreds of millions of dollars of damage every year and has forced farmers and herdspeople to abandon wide areas of land across Africa. Using the Sterile Insect Technique (SIT), the campaign succeeded in completely ridding the island of the flies that carry the parasitic cattle disease trypanosomiasis.

Trypanosomiasis was considered the most serious livestock disease affecting farmers on Zanzibar. The tsetse fly also transmits "sleeping sickness" - a potentially fatal disease affecting people. Twenty-two species of the fly infest an area of 10 million square kilometres in 36 countries in sub-Saharan Africa. Direct losses from bovine trypanosomiasis in Africa are estimated to range from US$600 million to US$1.2 billion every year.

The SIT was used in Zanzibar during a four-year campaign in which the Joint FAO/IAEA (International Atomic Energy Agency) Division cooperated with the Government of Tanzania. The campaign, which started in 1994, was the last step in a ten-year battle to rid the island of the tsetse fly. It was made feasible through FAO/UNDP (United Nations Development Programme) control activities which, by using conventional methods - such as treating cattle with pesticides - first brought tsetse populations down to levels that made eradication using the SIT a viable option.

For the Zanzibar campaign, tsetse mass-breeding technology and procedures developed at the FAO/IAEA Agriculture and Biotechnology Laboratory in Seibersdorf, Austria, were transferred to the Tsetse and Trypanosomiasis Research Institute (TTRI) in Tanga, Tanzania. TTRI held the largest tsetse facility in the world - with a female fly colony of nearly 1 million insects that produced an average of 70 000 sterile males every week. Almost 8 million sterile male flies were released during the eradication campaign.

A tsetse fly: now eradicated from Zanzibar

At the end of 1997, an independent expert group confirmed that, since September 1996, not a single wild fly had been captured in the once heavily infested areas of Zanzibar. In addition to monitoring the presence of the fly, which is small and difficult to find, routine blood samples are being taken from cattle in once-infested areas to be tested for trypanosomiasis. If no cases of the disease are identified over an extended period of time, this will confirm that the tsetse fly has indeed been eradicated.

The 50 km journey across to the mainland is too long for the tsetse fly to travel, even with a strong favouring wind. So the island will remain tsetse-free if precautions are taken to ensure that the flies are not reintroduced as stowaways on shipments from the mainland.

"Zanzibar was an ideal setting to demonstrate the feasibility of integrating the SIT with conventional methods in an area-wide approach," explained Dr Udo Feldmann of the Joint FAO/IAEA Division. "The fact that only one species of tsetse, Glossina austeni, was present on the island and the isolated location of Zanzibar promised sustainable results." Low-cost, local production of the fly was also important to the success of the operation.

22 May 1998

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