Introduction: development of the sterile insect technique for African malaria vectors

Malaria Journal BioMed Central Introduction Open Access Introduction: development of the sterile insect technique for African malaria vectors Waldemar Klassen Address: Tropical Research and Education Center, University of Florida, Homestead, Florida 33031, USA Email: Waldemar Klassen - Published: 16 November 2009 <supplement> and Tropical Medicine. <title> <p>Development His scientific efforts of the to control sterile insect vector-borne technique diseases for African continually malariafocused vectors</p> on maximizing </title> <editor>Mark humanitarian outcomes.</note> Q Benedict, Alan S</sponsor> Robinson and <note>Reviews</note> Bart GJ Knols</editor> </supplement> <sponsor> <note>This supplement is dedicated to Prof. Chris Curtis (1939-2008) of the London School of Hygiene Malaria Journal 2009, 8(Suppl 2):I1 doi:10.1186/1475-2875-8-S2-I1 This article is available from: http://www.malariajournal.com/content/8/S2/I1 © 2009 Klassen; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This supplement to Malaria Journal meets a great need for a convenient assemblage of existing information on the suppression and/or eradication of Anopheles populations using the release of sterilized mosquitoes. Publication of such a collection of articles is overdue for three compelling reasons. Firstly, because malaria control in sub-Saharan Africa, where 90 percent of the 300 to 500 million malaria cases and one to three million deaths occur from malaria each year, still depends on only two technologies for vector intervention: indoor residual spraying and insecticide-treated bed nets. Secondly, considerable research and development on the suppression of mosquitoes with the sterile insect technique (SIT) was conducted from the mid-1950s to the mid-1970s. However, nearly all of the scientists who pioneered this approach have retired and several of the greatest have died. While the benefit of the input, judgement and guidance can be provided from current experts in this field, a record of the key contributions of people like Chris Curtis, Ed Knipling and Don Weidhaas has thus far not been assembled. Thirdly, there are now new technologies available to support areawide integrated pest management (AW-IPM) programmes and much experience has been gained with the implementation of these programmes against major insect pests that could be applied to mosquito control [1,2]. In Europe, north of the Alps and Pyrenees, and in the United States, malaria began to decline in the mid 1800s as a result of drainage of swamps, use of screens to exclude insects on windows and doors, increased availability of quinine, increased literacy and improved education and general increase in economic well-being [3]. Endemic malaria in the USA largely disappeared without the eradication of the anopheline vectors in the late 1940s, when malaria cases were aggressively treated and large areas sprayed with DDT. Eradication of endemic malaria in the USA probably would have been accomplished even without DDT. Malaria is transmitted only by mosquitoes in the genus Anopheles and in sub-Saharan Africa, most transmission from infected to healthy people is accomplished by three anopheline species, Anopheles arabiensis, Anopheles funestus and Anopheles gambiae, with An. gambiae being the most important. Anopheles gambiae was eradicated in Brazil in 1940 [4] and from Egypt in 1945 [5]. Also, because most mosquitoes readily enter human dwellings and rest on walls and ceilings, it was found that they could be killed through applications of residual insecticides to these surfaces. Thus, in the 1930s de Meillon in South Africa had shown that malaria could be controlled by frequent spraying of the walls and ceilings of dwellings with pyrethrins [6], and this was substantiated by work in India [7]. The effectiveness of such residual treatment was found to be vastly prolonged by the use of DDT [8]. Residual treatment was found to result in the complete interruption of transmission in Cyprus, Greece, Italy, Sardinia, Taiwan, Venezuela and the USA. These historic achievements induced confidence that worldwide eradication of malaria through vector control was feasible. Thus, in 1955, the World Health Assembly launched the Global Malaria Eradication Programme with applications of DDT within dwellings being the primary stratagem [9]. Page 1 of 4 (page number not for citation purposes) Malaria Journal 2009, 8(Suppl 2):I1 http://www.malariajournal.com/content/8/S2/I1 Eradication of malaria was accomplished in due course in the temperate areas of Europe and Asia, in some subtropical areas, the Mediterranean Basin, and the southern USA, and on a number of the tropical islands of the Caribbean [8], and malaria was greatly reduced in Brazil and India. Spectacular progress was made in Sri Lanka, where the number of cases was reduced from a high of two or more million cases each year in 1958 to just 17 in 1963. In 1964 spraying was halted and the consolidation phase of the Programme was implemented. Meanwhile, newly discovered gem fields attracted large numbers of miners into the previously malaria endemic area who dug large numbers of pits in search of gem-stones. The soon-abandoned pits filled with water and became the source of dense populations of Anopheles culicifacies, the main malaria vector [10]. In 1967 malaria resurged strongly and spraying was resumed, but the dense vector population was found to have become resistant to DDT. Malathion was substituted, but it was objectionable to some families, required more frequent applications and was more expensive. Thus, the battle was lost and the incidence of malaria grew to more than 500,000 cases each year [3]. of vectors and humans from untreated sites was not considered to have been a significant factor in causing such unsatisfactory suppression of malaria. The primary reason for the lack of high efficacy of the residual treatment approach was found to be the tendency of the vectors to rest outdoors after blood feeding (exophily). Even the addition of mass drug administration at frequent intervals with strong community participation failed to halt transmission, although it did reduce the incidence of malaria to very low levels. Thus in such areas where ecological conditions support extremely high vector populations, the combination of residual treatment and drug administration cannot halt transmission. As described above, some economic development has diminished transmission, but certain ecological changes, which attend economic development, strongly favour the population growth of Anopheles species. In particular, water development projects (dam construction, expanded irrigation, production of wetland rice) tend to create id (...truncated)