The New World Screwworm eradication programme in North Africa

Abstract

The New World Screwworm (NWS, Cochliomyia hominivorax) is an obligate parasite of warm-blooded animals. The female lays up to 300 eggs in any break in the skin, and the resulting larvae (screwworms) burrow into surrounding living flesh. Infested animals frequently die, while the annual cost of controlling the pest in domestic animals is about US$ 10 per head. NWS is endemic in tropical Latin America. In 1988, it was detected in Libya, presumable introduced with imported sheep. By 1990, the infestation had spread to an area of 25,000 km² containing some 2 million livestock. In early 1991, an internationally funded eradication programme was undertaken by FAO, using sterile insects. Each week, 40 million pupae were flown from a production plant in Mexico, and the emerged adults were distributed by over the infested area. Within a few months, the infestation has been eradicated. Whereas 12,000 infested animals were found in 1990, only 6 were detected in 1991. The programme involved the shipping and distribution of 1.3 billion sterile insects, animal inspections totalling 40 million and laboratory examination of 280,000 trapped flies. While the programme cost close to US$ 75 million, a benifit/cost ration of 50:1 has been estimated.