Medical and Veterinary Entomology (2009) 23 (Suppl. 1), 1–7 Enabling technologies to improve area-wide integrated pest management programmes for the control of screwworms A. S. ROBINSON , M. J. B. VREYSEN , J. HENDRICHS and U. FELDMANN Joint Food and Agriculture Organization of the United Nations/International Atomic Energy Agency (FAO/IAEA) Programme of Nuclear Techniques in Food and Agriculture, Vienna, Austria Abstract . The economic devastation caused in the past by the New World screwworm fly Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) to the livestock indus- try in the U.S.A., Mexico and the rest of Central America was staggering. The eradication of this major livestock pest from North and Central America using the sterile insect tech- nique (SIT) as part of an area-wide integrated pest management (AW-IPM) programme was a phenomenal technical and managerial accomplishment with enormous economic implications. The area is maintained screwworm-free by the weekly release of 40 million sterile flies in the Darien Gap in Panama, which prevents migration from screwworm- infested areas in Columbia. However, the species is still a major pest in many areas of the Caribbean and South America and there is considerable interest in extending the eradica- tion programme to these countries. Understanding New World screwworm fly popula- tions in the Caribbean and South America, which represent a continuous threat to the screwworm-free areas of Central America and the U.S.A., is a prerequisite to any future eradication campaigns. The Old World screwworm fly Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) has a very wide distribution ranging from Southern Africa to Papua New Guinea and, although its economic importance is assumed to be less than that of its New World counterpart, it is a serious pest in extensive livestock production and a constant threat to pest-free areas such as Australia. In the 1980s repeated introductions and an expansion of Old World screwworm populations were reported in the Middle East; in the 1990s it invaded Iraq and since late 2007 it has been reported in Yemen, where a severe outbreak of myiasis occurred in 2008. Small-scale field trials have shown the po- tential of integrating the SIT in the control of this pest and various international organiza- tions are considering using the release of sterile insects as part of an AW-IPM approach on a much wider scale. Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae) is a screwworm of temperate regions, which, although of limited agricultural importance, has invaded several new locations in the past few years. This special issue reports on the re- sults of a 6-year project funded by the Joint Food and Agriculture Organization of the United Nations/International Atomic Energy Agency (FAO/IAEA) Programme of Nuclear Techniques in Food and Agriculture entitled ‘ Enabling Technologies for the Expansion of the SIT for Old and New World Screwworm’ . A major goal of the project was to better understand population genetic variation in screwworms as an aid to the identification of isolated populations. The project also addressed issues related to genetic sexing, cuticular hydrocarbons, population dynamics, genetic transformation and chromosome analysis. Key words . genetic sexing, population genetics, screwworm , sterile insect technique. Correspondence: Dr A. S. Robinson, Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, Wagramerstrasse 5, A-1400 Vienna, Austria. Tel.: + 43 1 2600 28402; Fax: + 43 1 2600 28274; E-mail: [email protected] Journal compilation © 2009 The Royal Entomological Society No claim to original government works 1 2 A. S. Robinson et al. Introduction temperature-dependent; in Texas it fluctuated between 7 days in summer to over 50 days in winter. The lifecycle is short and can Different species of screwworm are responsible for traumatic be completed in 21 days under optimal conditions. myiasis in many parts of the tropical, subtropical and temperate Larvae from a single oviposition can kill smaller animals and world. In the New World, successful area-wide integrated pest multiple infections can kill mature cattle. Therefore, larval management (AW-IPM) programmes including the use of the screwworm infestations have serious economic implications for sterile insect technique (SIT) have led to the eradication of the the livestock industry. Local conditions such as the distribution New World screwworm Cochliomyia hominivorax (Coquerel) and density of livestock and wildlife populations, husbandry from the southern U.S.A., Mexico, Central America, Panama and practices, commercial movement of animals, human population some islands in the Caribbean. The species occupying a similar density, socioeconomic conditions, public health services, climatic ecological niche in the Old World are Chrysomya bezziana Vil- factors and geography dictate the severity of the infestations leneuve and, in more temperate regions, Wohlfahrtia magnifica and the economic magnitude of the problem. The eradication of (Schiner). There is evidence that the latter two species are C. hominivorax from the U.S.A., Mexico and the remainder of expanding their distributions into new areas. The success of Central America is undoubtedly the most successful example AW-IPM programmes with an SIT component in control of of the application of the SIT as part of an AW-IPM programme. C. hominivorax , coupled with the significance of the damage In 2000, the programme’ s direct annual producer benefits were wrought by screwworm pests, has encouraged other countries estimated at US$ 896 m, US$ 328 m and US$ 87 m for the and regions to consider using a similar approach. Expansion of U.S.A., Mexico and Central America, respectively ( Vargas-Terán the approach to new regions and species will benefit from im- et al. , 2005 ). Adding the positive effect on the general economy proved information on potential target populations and from the increases the annual benefits to more than US$ 4 bn for the en- development of improved strains for release. tire screwworm-free zone (Wyss, 2002). To prevent reinvasion In support of future AW-IPM programmes against these from South America, a biological buffer zone has been estab- screwworm pests, the Joint Food and Agriculture Organization lished through the weekly release of 40 million sterile flies in of the United Nations/International Atomic Energy Agency the Darien Gap, Panama. (FAO/IAEA) Programme of Nuclear Techniques in Food and However, this screwworm-free region remains at risk because Agriculture funded a 6-year co-ordinated research project (CRP) of endemic populations in the Caribbean; C. hominivorax re- entitled ‘ Enabling Technologies for the Expansion of the SIT mains one of the major livestock and wildlife pests in Cuba, the for Old and New World Screwworm ’ , with the participation of Dominican Republic and Haiti, the economies of which are still 11 scientists from nine countries. The results of this CRP are re- dominated by agriculture. The Caribbean territories affected by ported in this special issue. A major goal of the CRP was to bet- C. hominivorax have a total surface area of 203 460 km2 and the ter understand population genetic variation in screwworms as an total annual costs in treatment and prevention are estimated to aid to the identification of isolated populations as targets for exceed US$ 75 m (1999 figures) ( Vargas-Terán & Novy, 2001 ). AW-IPM programmes. The CRP also addressed issues related to Furthermore, the species is highly mobile and individual flies genetic sexing, cuticular hydrocarbons and mating compatibility, have been recorded travelling 290 km ( Spradbery, 1994 ). In ad- population dynamics, genetic transformation and chromosome dition, there is some evidence that flies may be carried by wind analysis. This special issue is devoted to the results generated to infest new areas, as is suspected to have been the case in the during the CRP, together with several invited contributions. re-infestation of the Virgin Islands in 1977 ( Rawlins, 1985 ). However, the most common way for the fly to be introduced is through the movement of larvae-infested animals or humans, as The species was demonstrated by its accidental introduction into the Libyan Arab Jamahiriya in 1988 ( Lindquist et al. , 1992 ). The presence The New World screwworm fly is a major parasitic pest of of C. hominivorax in the Caribbean poses a constant threat of warm-blooded hosts which causes primary myiasis in wildlife, re-infestation to countries in the region where the pest is non- livestock, pets and humans. Humans living in conditions of poor endemic or has been eradicated and this is becoming especially hygiene are particularly at risk, and the infestation can become significant with increased international trade and globalization. rapidly debilitating when it occurs in the nasal and frontal si- The costs of eradication from the Caribbean territories using an nuses, eyes, ears or mouth. The pest is, however, mainly present AW-IPM strategy were estimated in 2001 to be US$ 140 m ( Vargas- in livestock, as was demonstrated in 1935 when 230 000 cases Téran & Novy, 2001 ). Cochliomyia hominivorax is also present were detected in livestock in Texas, compared with only 55 in in all countries in South America, with the exception of Chile, humans ( FAO, 1992 ). Gravid female screwworm flies are at- and it has been estimated that the potential annual producer ben- tracted to open wounds caused either by animal husbandry prac- efits following eradication would be US$ 2.8 bn ( Wyss, 2002 ). tices (dehorning, castration etc.) or occurring naturally (e.g. tick Before embarking on such programmes, it is important to gener- bites). A female oviposits on average 200 eggs in single or mul- ate the required baseline information on the distribution, genet- tiple egg masses in the vicinity of the wound. First instar larvae ics and mating compatibility of populations in this region. hatch after 11 – 24 h and start feeding immediately on living tis- The Old World screwworm fly Ch.