Onchocerciasis: shift from control to elimination - Vector control shall not remain under a bushel! Moses Katabarwa1 and Frank O. Richards1 The Carter Center, Atlanta, GA USA ASTMH 64th Annual Meeting - October 25-29, 2015 - Philadelphia, PA USA # 451 Possible reasons for the failure Background Justification of Vector Control Possibly unreliable treatment coverage (desired treatment coverage: ≥65% of total population or 90% of eligible population).  NB: Good treatment coverage in a number of cases resulted in transmission interruption. Infection may remain even under effective treatment coverage at levels where diagnostically would be declared at Zero (Duerr et al, 2011). Vector Related Factors: - Impact of potential breeding sites and their productivity across the seasons - Capacity of various vector species to migrate / undefined transmission zones - Capacity of vectors to transmit the parasite efficiently Since 1987, the approach to control human onchocerciasis shifted from large scale aerial spraying of larvicide to annual mass treatment with the drug ivermectin (Mectizan®). The African Program for Onchocerciasis Control (APOC) focused on Community Directed Treatment with ivermectin (CDTI), where community members are trained and utilized to treat their respective community members. However, in the era of onchocerciasis elimination, vector control should be considered as a complementary tool for accelerating interruption of transmission as it: encourages best practices in mapping breeding sites and clearly defining transmission zones; focuses on identification of the vector species in specific geographical areas, and determines their individual competences; focuses on geographic areas where the resources are most needed. There are examples of vector control/elimination successfully accelerating the interruption of transmission and disease elimination. Where the focus is isolated, there is a high chance of achieving elimination of the vector and transmission interruption. Where there is very high biting vector density, it reduces transmission and accelerates elimination of onchocerciasis in conjunction with other control measures. Where there is need to accelerate elimination because of late start of mass treatment with ivermectin. It is an important way forward in areas of onchocerciasis transmission that have concomitant Loa loahyper-endemicity. Examples of vector elimination in Uganda Kashoya-Kitomi focus Uganda: Foci where vector control or elimination has been applied Recent developments Ground Larviciding began in August, 2007 Countries have begun to demand a policy on nationwide elimination of onchocerciasis in Africa. Those that have already launched policies: Sudan (2006) Uganda (2007) Ethiopia (2012) Nigeria (2014) Ground Larviciding Stopped in October, 2010 Nyagak-Bondo focus Concerns from endemic countries after over 10 years of annual mass treatment with ivermectin The last fly was caught in August 2012 How long will annual mass treatment go on? Can an annual dose of ivermectin interrupt transmission? With competing urgent public health needs and policies, can annual mass treatment be sustained indefinitely by national governments? Will ivermectin for twice yearly treatment be available any time it is required? How can transmission interruption be accelerated so that elimination is achieved in a shorter period in a cost efficient manner? Is there a risk of development of resistance against ivermectin? Ground Larviciding began in June, 2012 Ground Larviciding stopped in October, 2013 Reasons for launching elimination policy Evidence of failure for an annual dose of ivermectin to interrupt transmission in: References It is not cost efficient to sustain onchocerciasis control policy indefinitely. The emphasis of ivermectin in the control mode could result in drug resistance in the long term. Success in eliminating onchocerciasis in the Americas and in some foci in Africa calls for a change in the approach. Evidence shows that elimination takes a short time and with twice yearly treatment can be attained in 6.5 years or less (Cupp and Cupp, 2005). The stated goal is to attain elimination in most of Africa by 2025. Vector control directed against Simulium larval stages through ground larviciding using WHO-approved and environmentally safe insecticides was successful in eliminating S. yahense (Bioko Island, Guinea Bissau), and S.neavei (Itwari and Mt. Elgon foci of Uganda, 2003 and 2008, respectively). 1. Cupp EW, Cupp MS (2005). Short report: impact of ivermectin community-level treatments on elimination of adult Onchocerca volvulus when individuals receive multiple treatments per year. Am J Trop Med Hyg. 73, 159-61. 2. Duerr HP1, Raddatz G, Eichner M (2011) . Control of onchocerciasis in Africa: threshold shifts, breakpoints and rules for elimination. Int J Parasitol. 41(5):581-9. doi: 10.1016/j.ijpara.2010.12.009 3. Garms R, Lakwo TL, Ndyomugyenyi R, Kipp W, Rubaale T, Tukesiga E, Katamanywa J, Post RJ, Amazigo UV (2009). The elimination of the vector Simulium neavei from the Itwara onchocerciasis focus in Uganda by ground larviciding.Acta Trop. 2009 Sep;111(3):203-10. doi: 10.1016/j.actatropica.2009.04.001 4. Katabarwa MN, Eyamba A, Nwane P, Enyong P, Yaya S, Baldiagaï J, Madi TK, Yougouda A, Andze GO, Richards FO (2011). Seventeen years of annual distribution of ivermectin has not interrupted onchocerciasis transmission in North Region, Cameroon. Am J Trop Med Hyg. 85(6):1041-9. doi: 10.4269/ajtmh.2011.11-0333. 5. Osei-Atweneboana M Y, Eng JK, Boakye DA, Gyapong JO, Prichard RK (2007). Prevalence and intensity of Onchocerca volvulus infection and efficacy of ivermectin in endemic communities in Ghana: a two-phase epidemiological study. Lancet 16, 369(9578):2021-9. 6. Wanji S1, Akotshi DO, Mutro MN, Tepage F, Ukety TO, Diggle PJ, Remme JH (2012). Validation of the rapid assessment procedure for loiasis (RAPLOA) in the Democratic Republic of Congo. Parasit Vectors. doi: 10.1186/1756-3305-5-25. Abu Hamad focus of Sudan in 9 years West region of Cameroon in 15 years North region of Cameroon in 17 years Nyagak-Bondo focus of North West Uganda in 18 years Gami village in Central African Republic in 20 years For governments with many needs and limited resources, interrupting transmission and eliminating the disease in the shortest time possible is attractive to decision makers who control policies and budgets. Existence of areas that have never been treated and need to be brought to speed with elimination targets: Map of Uganda – Current Epidemiological Status (August 2014) For a long time there was a myth that hypo-endemic areas did not have indigenous transmission and therefore did not need treatment. If meso-endemic ( ≥20 to <40 nodule prevalence) and hyper-endemic (≥40% nodule prevalence) were eliminated, hypo-endemic areas would disappear naturally. This belief is now known to be false. There have been discoveries of new onchocerciasis-endemic areas. In some areas where co-endemicity for onchocerciasis and Loa loa infections exists, treatment with ivermectin is not possible due to severe adverse events. These areas are a potential source of re-infection. Acknowledgements The authors would like to acknowledge all individuals, institutions and donors who have understood the complementary role of vector control in the elimination of onchocerciasis and are at the forefront of supporting it materially and financially. Special acknowledgement to BASF for providing Abate (Temophos TM), LCIF, Al Waleed, and The Carter Center who have supported vector control in Uganda. WHO programme APOC applied vector control for onchocerciasis elimination in some foci in Tanzania and Uganda, and eliminated transmission in Bioko Island.