Problem Statement: The New World screwworm fly (NWS), Cochliomyia hominivorax (Diptera: Calliphoridae), is an obligate parasite (i.e. cannot live independently of its host) of warm-blooded vertebrates during its larval stages. The feeding activity of its larvae on living tissues of the host causes serious injury and can result in death. The pain and suffering caused by even mild infestations makes NWS an important animal welfare problem. The hosts most commonly infested are larger mammals, including wildlife and domestic livestock, although humans can also be infested. In the spring of 1998 numerous infestations of livestock by NWS were found in the Libyan Arab Jamahiriya (Libya), the first time that this species had become established outside of the Americas. This establishment was not just an emergency situation for Libya, but also represented a wider threat to North Africa, the Mediterranean Basin and possibly further afield.

Methods: The parasite was identified as NWS by light microscopy techniques, using standard taxonomic identification keys and reference to specimens in museum collections of international coverage. Because of the potentially serious consequences of this introduction, international organisations concerned with agriculture, including the Food and Agriculture Organisation of the United Nations (FAO) and the United States Department of Agriculture (USDA), were notified. This action led to the raising of international awareness and an eradication programme was developed. As local veterinarians and entomologists were unfamiliar with the NWS, taxonomists from the Natural History Museum (UK) participated in regional training courses and produced clear and simple identification guides.

Outcomes and Impacts: The entire eradication programme in Libya cost some US$80 million, including a major input from Libya equivalent to US$7.5 million. However, the benefit:cost ratio for the region was estimated to be at least 50:1. Accurate taxonomic identification at the outset enabled the programme to be launched swiftly and continuing taxonomic input helped focus the programme during its operation. If the programme had been launched late or had failed, then NWS could have spread much further in the region with far greater economic and human and animal health consequences.

Lessons: The main taxonomic issue was early and accurate identification of an introduced pest species and recognition of the potentially disastrous consequences it posed in an uncontrolled new environment. Thereafter, the important issue was to raise the identification skills of local scientists. Accurate identification of larval and adult specimens from infestations and traps was vital to monitoring and directing the eradication programme, ultimately saving billions of dollars in impacts such as stock losses, human health and eradication programmes.