Role of vector control in the global program to eliminate lymphatic filariasis Bockarie, Moses J.; Pedersen, Erling Møller; White, Graham B.; Michael, Edwin Published in: Annual Review of Entomology DOI: 10.1146/annurev.ento.54.110807.090626 Publication date: 2009 Document version Publisher's PDF, also known as Version of record Citation for published version (APA): Bockarie, M. J., Pedersen, E. M., White, G. B., & Michael, E. (2009). Role of vector control in the global program to eliminate lymphatic filariasis. Annual Review of Entomology, 54, 469-487. https://doi.org/10.1146/annurev.ento.54.110807.090626 Download date: 23. sep.. 2021 ANRV363-EN54-24 ARI 7 November 2008 11:5 Role of Vector Control in the Global Program to Eliminate Lymphatic Filariasis Moses J. Bockarie,1 Erling M. Pedersen,2 Graham B. White,3 and Edwin Michael4 1Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom; email: [email protected] 2DBL-Center for Health Research and Development, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark; email: [email protected] 3Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32608; email: gbwhite@ufl.edu 4Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom; email: [email protected] Annu. Rev. Entomol. 2009. 54:469–87 Key Words First published online as a Review in Advance on mosquito ecology, mass drug administration, mathematical modeling, September 17, 2008 insecticide treated nets, integrated vector management The Annual Review of Entomology is online at ento.annualreviews.org Abstract This article’s doi: Lymphatic filariasis (LF) is a major cause of acute and chronic morbid- 10.1146/annurev.ento.54.110807.090626 by NESLi2 on 04/30/09. For personal use only. ity in the tropical and subtropical parts of the world. The availability of Copyright c 2009 by Annual Reviews. safe, single-dose, drug treatment regimens capable of suppressing mi- All rights reserved crofilaremia to very low levels, along with improvements in techniques 0066-4170/09/0107-0469$20.00 for diagnosing infection, has resulted in the targeting of this major mosquito-borne disease for global elimination. The Global Program to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the Annu. Rev. Entomol. 2009.54:469-487. Downloaded from arjournals.annualreviews.org principal objective of breaking the cycles of transmission of Wuchereria bancrofti and Brugia spp. through the application of annual mass drug administrations (MDAs) to entire at-risk populations. Although signif- icant progress in initiating MDA programs in endemic countries has been made, emerging challenges to this approach have raised questions regarding the effectiveness of using MDA alone to eliminate LF without the inclusion of supplementary vector control. Here, we review advances in knowledge of vector ecology, vector-parasite relationships, and both empirical and theoretical evidence regarding vector management to as- sess the feasibility and strategic value of including vector control in the GPELF initiative to achieve the global elimination of LF. 469 ANRV363-EN54-24 ARI 7 November 2008 11:5 LYMPHATIC FILARIASIS remarkable improvements in techniques for di- agnosing infection, resulted in advocacy for a Lymphatic filariasis (LF) is a major cause of global strategy to eliminate the disease through LF: lymphatic acute and chronic morbidity affecting humans MDA (16, 49). This led in 1997 to the land- filariasis in tropical and subtropical areas of Asia, Africa, mark adoption by the World Health Assembly Mf: microfilaremia the Western Pacific, and some parts of the of Resolution WHA50.29 calling for the elim- Americas. More than 1.2 billion people are es- Mass drug ination of LF as a public health problem glob- administration timated to live in areas where they are at risk ally. As a result, in 2000 the World Health Or- (MDA): for the disease (86), and of the 120 million ganization, in collaboration with other inter- community-wide actual cases of LF currently thought to oc- treatment of national agencies from the public health and cur in 83 endemic countries, 91% are caused individuals with private sectors, formed a global alliance (84) by Wuchereria bancrofti while Brugia malayi and antiparasitic drugs and launched a global campaign to eliminate regardless of the B. timori infections account for the other 9% LF by the year 2020 (87). The main goal of the infection status of each (42, 43, 66). These lymphatic-dwelling par- Global Program to Eliminate Lymphatic Filar- individual asites can cause severe damage to the lym- iasis (GPELF) is to break the cycle of trans- GPELF: Global phatic system, resulting in the development of mission of the parasites between mosquitoes Program to Eliminate lymphedema, genital pathology (especially hy- Lymphatic Filariasis and humans, mainly through MDA with al- droceles), and elephantiasis in some 41 mil- bendazole (ALB) in combination with either ALB: albendazole lion men, women, and children (85). A fur- ivermectin (IVR) or diethylcarbamazine citrate DEC: ther 76 million have hidden internal damage (DEC) (53, 83, 84). The Ministries of Health diethylcarbamazine to their lymphatic and renal systems. The fi- citrate of all 83 countries afflicted with LF are now larial parasites have biphasic life cycles involv- committed to taking action by setting up their Limitation: a ing the definitive mammalian host and various negative feedback own national elimination programs. By the end genera of mosquito vectors, including Anophe- process in which a of 2006, 44 of the 83 endemic countries had les, Aedes, Culex, Mansonia, and Ochlerotatus. parasite (at any stage) implemented MDA (86). compromises the W. bancrofti appears to be exclusively a human success of parasites at parasite, whereas Brugia spp. are zoonotic in the same or another limited situations. Parasite transmission is indi- stage CHALLENGES TO rect and occurs through the bite of an infective MDA CAMPAIGNS mosquito containing third-stage infective lar- Despite the progress made in initiating MDA vae (L3) that have developed through two inter- by NESLi2 on 04/30/09. For personal use only. programs, a number of challenges to these pro- mediate stages (L1 and L2) from microfilaremia grams have begun to appear. First, many coun- (Mf ) ingested with the blood meal taken by fe- tries initiating MDA have not reached national male mosquitoes on an infected human. scale even after 5–6 years and some countries face major challenges in sustaining MDA, prin- cipally as a result of significant resource con- Annu. Rev. Entomol. 2009.54:469-487. Downloaded from arjournals.annualreviews.org GLOBAL PROGRAM TO straints (86). Resource limitations and avail- ELIMINATE LYMPHATIC ability of rapid diagnostic tests have hampered FILARIASIS: EVOLUTION progress in mapping implementation units for AND CURRENT STATUS MDA. Delivering MDA in urban areas has also The absence of a nonhuman reservoir for posed operational challenges. Second, the ex- W. bancrofti and only minor animal hosts for act level and duration of treatments to achieve B. malayi means that transmission can be inter- LF elimination in different endemic regions re- rupted by reducing the Mf stage through mass main unknown (44, 45), such that it is diffi- drug administration (MDA) alone. This, along cult to predict or decide when to stop ongo- with the emergence of safe, single-dose, two- ing MDA programs. Third, a major challenge drug treatment regimens capable of reducing to implementing MDA at a level required to Mf to very low levels for one year or more and meet elimination targets within a reasonable 470 Bockarie et al. ANRV363-EN54-24 ARI 7 November 2008 11:5 time frame has been the difficulty of achieving and transmitted by the same mosquitoes (58). the required high drug coverages in endemic Similarly, vector intervention measures to con- communities (57). Fourth, there has been a shift trol dengue are in place in many parts of the Parasite control: recently toward linking MDA for LF control world where Aedes mosquitoes transmit LF (13). reduction of infection with programs for controlling other neglected Thus, an integrated strategy involving vector incidence, prevalence, tropical diseases, such as schistosomiasis, soil- control is now thought to have great potential or morbidity to a transmitted helminthiasis, and onchocerciasis to become an important supplementary compo- locally acceptable level (31, 48). This integrated approach is proving nent of the filariasis elimination strategy. Here, at which the parasitic infection is no longer to be an attractive alternative to an individual we review advances in knowledge of vector ecol- considered a public programmatic approach, because it is perceived ogy, vector-parasite relationships, population health problem to remove duplication of effort and costs in pro- dynamics of vector-based interventions, and in- Parasite elimination: grams that share common activities. However, tegrated control involving antimosquito mea- reduction of the with different objectives (e.g., parasite con- sures such as residual house spraying and dis- incidence of infection trol versus parasite elimination) and the poten- tribution of LLITNs to evaluate the feasibility to zero in a defined tial increased complexity in drug delivery (e.g., and strategic value of including vector control geographic area move