After 70 years of fighting an age-old scourge, onchocerciasis in Uganda, the end is in sight

After 70 years of fighting an age-old scourge, onchocerciasis in Uganda, the end is in sight Abstract Onchocerciasis causes severe itching, serious skin disease and ocular damage leading to visual impairment or permanent blindness. It is associated with hanging groin, epilepsy, Nakalanga dwarfism and, most recently, nodding disease. This disease affected communities in 17 transmission foci in 37 districts of Uganda, where about 6.7 million people are once at risk. The efforts against onchocerciasis in Uganda commenced in the late 1940s, when vector control was launched using dichlorodiphenyltrichloroethane; by 1973, Simulium damnosum had been eliminated in the Victoria focus. Success outside of the Victoria focus was short-lived due to changes in government priorities and the political upheavals of the 1970s and 1980s. With the return of political stability, annual treatment with ivermectin through mass drug administration was launched in the early 1990s. Control of the disease has been successful, but there has been failure in interrupting transmission after more than 15 years. In 2007 Uganda launched a nationwide transmission elimination policy based on twice-per-year treatment and vector control/elimination, with a goal of eliminating river blindness nationwide by 2020. By 2017, 1 157 303 people from six foci had been freed from river blindness. This is the largest population ever declared free under World Health Organization elimination guidelines, providing evidence that elimination of river blindness in Africa is possible. Onchocerciasis, Control, Elimination, Larvicide, Ivermectin Introduction Human onchocerciasis is caused by the filarial nematode Onchocerca volvulus, which is transmitted by the bites of Simulium flies that breed in fast-flowing rivers, hence its common name in Africa, ‘river blindness.’ Unlike in West Africa, onchocerciasis is a highly focal disease in East and Central Africa, Yemen and the Americas. The disease can cause severe itching, skin lesions and eyesight impairment, and can lead to permanent blindness when not treated.1 It has been hypothesized that onchocerciasis is responsible for a condition known as ‘Nakalanga syndrome,’ a form of dwarfism that is observed in some parts of Uganda with high onchocerciasis prevalence rates,2,3 and has been associated with epilepsy and ‘nodding syndrome.’4 In addition, ‘hanging groin’ and hernia are also known complications of the disease. Early history of onchocerciasis in Uganda In the late 1950s it was estimated that at least 1.18 million people out of a total population of 6.5 million living in Uganda were at risk of being infected with onchocerciasis.5 About 40% (472 000) of the at-risk population were estimated to be infected with onchocerciasis. In Uganda, the vectors of onchocerciasis include Simulium neavei, which develops in a phoretic association with freshwater crabs, and members of the Simulium damnosum complex.5 It is known that S. damnosum thrives at low altitudes and in warm, open, fast-running rivers and streams. S. damnosum has a long flight range of 45 to 65 km from its breeding sites and does not need corridors of bush for protection.6 In contrast, S. neavei requires a closed canopy that provides shade to migrate and tends to breed at a higher altitude than S. damnosum. S. neavei is usually found in moist, cool, green forests, as well as riverine fringing forest environments. Their flight range of less than 6 km is much less than S. damnosum.7 The main historical habitats for S. damnosum s.l. in Uganda during the 1950s were the Victoria Nile River, where Christy originally described S. damnosum, with almost 100% of the inhabitants afflicted with onchocerciasis; the Murchison Nile from the Atura River ending in Murchison Falls; and the Rwenzori focus that extended into the Democratic Republic of the Congo (DRC), with a prevalence of onchocerciasis ranging from 54 to 91%.6 Onchocerciasis transmitted by S. neavei was originally reported in the following areas of Uganda: Budongo Forest, where the baseline skin microfilaria (mf) rate for sawmill workers was 78%, and 46% among students in the forestry college8; Mount Elgon, where the baseline mf prevalence rate was 80%; West Nile, where the mf prevalence rate was 56%3; and Kigezi (now known as the Bwindi focus), where the prevalence rate was 80%9 (Figure 1). In 1973 a new onchocerciasis focus east and southeast of Lake George (now designated the Kashoya-Kitomi focus) was reported, but no prevalence rate was provided.10 Figure 1. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 1975.1 Figure 1. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 1975.1 Control of onchocerciasis (1950–1973) Previously, dichlorodiphenyltrichloroethane (DDT) was widely used for onchocerciasis control in Uganda. Successful intermittent control efforts in the Victoria Nile focus on the Nile River commenced in 1952.11,12 This resulted in S. damnosum elimination along a 70 km stretch of the Nile River between Lake Victoria and Lake Kyoga by 1973. In 1974, after a military coup, all the expatriate leaders of national vector control activities were forced to leave Uganda and further monitoring of the Victoria Nile focus was halted; however, activities by the Vector Control Division of the Ministry of Health continued there until 1977. In the Murchison Nile focus, a trial of DDT vector control of S. damnosum was attempted in 1959 to protect workers constructing a hydroelectric power station. After that trial a reinvasion by S. damnosum from Atura on the Murchison Nile was documented.13 In 1971, DDT larviciding was extended to cover the whole Rwenzori focus.13 In the Budongo S. neavei focus, the vector was nearly eliminated by 1962.14,15 Mass drug administration (MDA) with diethylcarbamazine citrate (DEC) was also provided.15 In the Mount Elgon focus, vector control was initiated in 1957, and in 1972 the prevalence was determined to have dropped to 5–10%. Vector control was also piloted in the West Nile focus in 1955.3 In the Kigezi onchocerciasis endemic area, DEC was provided to patients at health facilities until 1992, when the program introduced ivermectin through community-based MDA programs. There is no evidence that any vector control or MDA was carried out in the Kashoya-Kitomi onchocerciasis focus during this period. Re-establishment of the national onchocerciasis control program (1987–2006) In 1987, MSD, also known as Merck & Co., Inc., Kenilworth, NJ, USA, committed to donating ivermectin (Mectizan) ‘as long as necessary’ for the control of onchocerciasis, an event that coincided with the return of peace to Uganda. In 1989, the Uganda Foundation for the Blind, with Sightsavers’ funding, began mass treatment with ivermectin in the Budongo onchocerciasis focus. Treatment with ivermectin followed in the Itwara onchocerciasis focus of western Uganda in the Kabarole and Kyejonjo districts, with assistance from the German Technical Cooperation Agency (GTZ). However, it was not until mid-1992 that a comprehensive and systematic nationwide program was established, led by the Uganda Ministry of Health with support from the River Blindness Foundation (RBF). The Maracha-Terego focus in Maracha and Terego counties and the West Nile focus in the Maracha-Terego, Koboko and Yumbe districts provided treatment from 1993 to 1996, supported by the Christoffel Blinden Mission (CBM). Apart from northern Uganda, most onchocerciasis endemic areas were mapped during early and mid-1990s with support from the RBF and the United Nations Children’s Fund, United Nations Development Programme, World Bank and World Health Organization (WHO) Program for Research and Training in Tropical Disease Research (TDR). A nationwide rapid epidemiological mapping of onchocerciasis (REMO) based on rapid epidemiological assessment with nodule palpation in S. damnosum and S. neavei areas was conducted between 1993 and 1997 (Figure 2).16,17 In 1996, The Carter Center assumed responsibility for the RBF and later in the year a partnership program known as the African Programme for Onchocerciasis Control (APOC) was launched with World Bank trust funds and the WHO as its executing agency. By 1996 the Uganda Onchocerciasis Control Programme had received financial support from the APOC, Sightsavers (the Bulisa, Hoima and Masindi districts) and The Carter Center (assisting the other endemic districts in the country).18 Figure 2. View largeDownload slide REMO map of Uganda showing the status of onchocerciasis in 1996. Figure 2. View largeDownload slide REMO map of Uganda showing the status of onchocerciasis in 1996. Comprehensive assistance for community-directed treatment with ivermectin (CDTI) from the APOC was provided for 5 years. Afterwards, APOC financial support was more limited and focused on replacement of capital equipment and advocacy. The goal of the APOC and Uganda at the time was to control the disease as a public health problem by limiting the morbidity arising from the disease, thereby fostering economic development. The control approach was not expected to interrupt transmission of the infection, with the exception of two S. neavei foci (Mpamba-Nkusi and Itwara), where the APOC supported ground larviciding for vector elimination activities. These two foci made considerable progress, proving the durability of localized vector elimination in S. neavei areas after 2–3 years of larviciding.19,20 Inspiration from the Americas Uganda policymakers were concerned that the country, with more than 50 years of sporadic onchocerciasis control activities, could not continue with business as usual. With the return of peace and political stability nationwide, the government of Uganda was keen to break the legacy of onchocerciasis, interrupt its transmission and achieve national elimination. Noting that the 2001 Conference on Eradicability of Onchocerciasis at The Carter Center indicated the feasibility of onchocerciasis elimination in the Americas,21,22 Ugandan policymakers began to study the Onchocerciasis Elimination Program for the Americas (OEPA) twice-per-year treatment policy. In particular, rethinking onchocerciasis elimination gained traction with the publication of a report by Cupp and Cupp.23 In this report, data analysis from the Americas concluded that twice-per-year ivermectin MDA achieving ≥85% eligible population coverage reduced the lifespan of adult O. volvulus, leading to their demise within 6.5 years. A pilot onchocerciasis elimination project using twice-yearly ivermectin treatment in the Wadelai focus of Uganda conducted in 2005–2006 found that CDTI could attain a treatment coverage of at least 90% of the eligible population in both rounds.24 At the same time, a combination of vector control and ivermectin treatment in some foci was found to be an effective approach for rapid transmission interruption.25 In 2006, a delegation from the Ministry of Health of Uganda travelled to Guatemala to attend the Inter-American Conference on Onchocerciasis (IACO). While attending the IACO meeting, the Uganda delegation visited the Universidad del Valle de Guatemala/Centers for Disease Control laboratory that was providing laboratory-based molecular testing to verify progress towards elimination for OEPA. They learned about lab training and equipment requirements for conducting enzyme-linked immunosorbent assay (ELISA) tests for detecting IgG4 antibodies to the OV16 recombinant antigen and vector pool screening for O. volvulus DNA using the O-150 polymerase chain reaction (PCR).26 Energized by their visit, the delegates returned home determined to undertake a nationwide elimination effort in Uganda. A national elimination policy (2007–2016) The Uganda Ministry of Health crafted a new policy for nationwide onchocerciasis transmission elimination that was launched by the president of Uganda, His Excellency, Yoweri Museveni, at a national meeting held in Kampala in January 2007. The renamed Uganda Onchocerciasis Elimination Program (UOEP) had several charges. First, it was no longer business as usual, and all tools (ivermectin and vector control) were to be used in combination when and where necessary. Twice-per-year ivermectin treatment was to be the norm except in areas where once-per-year had been clearly effective in breaking transmission. Second, a molecular laboratory based on the Guatemala model was established to help monitor progress towards elimination. Third, an independent technical advisory committee, the Uganda Onchocerciasis Elimination Expert Advisory Committee (UOEEAC), was established to help the ministry progress towards nationwide elimination. Key assisting partners (The Carter Center, Lion Clubs of Uganda and Lion Clubs International Foundation [LCIF], Mectizan Donation Program and Sightsavers) would have seats on the UOEEAC. The UOEP and UOEEAC embarked on the following: Refining the onchocerciasis map and launching twice-per-year treatment The UOEP aggressively embarked on refining and completing the onchocerciasis map of Uganda in order to include any hypoendemic communities that may have been left untreated. Vector elimination was achieved in the Victoria focus and (likely) in the Itwara and Mpamba-Nkusi foci in 2007 (Figure 3). A population of 4.9 million people living in 37 districts were still at risk of onchocerciasis in 16 foci (not counting Victoria) and transmission interruption appeared to have been reached in the Nyamugasani, Maracha-Terego, Obongi, Imaramagambo, Itwara and West Nile foci. Twice-per-year treatment with ivermectin through CDTI continued in Wadelai and was launched in the Budongo, Bwindi, Kashoya-Kitomi, Mount Elgon and Mpamba-Nkusi foci in 2007, Wambabya-Rwamarongo in 2008 and later in Nyagak-Bondo (2012), Madi-Mid North (2013) and Lhubiriha (2015). Figure 3. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2007. Figure 3. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2007. Establishment of the molecular laboratory In 2008 the Ministry of Health provided space for the UOEP’s molecular laboratory at the Vector Control Division as well as personnel to run it. The Carter Center provided equipment and financial support to the laboratory and the University of South Florida laboratory trained the Uganda laboratory personnel. The new laboratory has allowed close monitoring of the impact of interventions on onchocerciasis transmission. Its experience, the largest operation among onchocerciasis molecular laboratories in Africa, has been published.26 By mid-2016 it had analysed more than 65 000 blood spot samples with the OV16 ELISA, as well as thousands of Simulium flies and skin snips from some foci using the O-150 PCR. The University of South Florida continues to ensure acceptable quality control standards. Uganda Onchocerciasis Elimination Expert Advisory Committee The UOEEAC held its first meeting in 2008. Its membership is comprised of the Ministry of Health (including representatives from district health services), non-governmental development organization partners and independent national and international experts on the disease. The WHO and Mectizan Donation Program representatives are usually in attendance as observers.27–29 The UOEEAC provides technical advice to the UOEP through review, monitoring and evaluation of each of the 17 foci and recommends effective approaches and methods for hastening onchocerciasis elimination. The UOEEAC also reviews strategic guidelines from various onchocerciasis global or regional technical committees and vets them from the Ugandan perspective. It meets once a year in Kampala, Uganda. The UOEEAC is charged with the provision of credible, independent and cutting-edge technical advice to help Uganda eliminate onchocerciasis by 2020. Second, the expert technical committee is entrusted with the responsibility of providing evidence-based recommendations on the progress of interruption of onchocerciasis transmission to the Ministry of Health for timely decision making. Recommendations from the UOEEAC flow to the National Certification Committee, a technical committee established in the hierarchy of the Ministry of Health structure. National criteria for determining the elimination of onchocerciasis in Uganda The first assignment of the UOEEAC was to formulate national guidelines for determining elimination in Uganda. The committee worked to synthesize two different sets of elimination criteria: those based on the 2001 WHO criteria for onchocerciasis elimination30 and those put forward by the APOC/TDR, as described by Diawara et al.31 and Traore et al.32 The UOEEAC drafted the national guidelines and the Ministry of Health reviewed and accepted them in 2011.27 In its review of the WHO and APOC guidelines the UOEEAC noted a lack of entomological indicators for S. neavei areas where elimination of the vector had been achieved. Thus the UOEEAC developed totally new guidelines that used crab collections as one of the principal monitoring elements. The UOEEAC defined S. neavei elimination indicators as a lack of positive crabs for larvae/pupae of S. neavei species in a series of surveys and the absence of adult flies collected in a defined focus over a period of 3 years implies interruption of transmission of onchocerciasis.27,29 The UOEEAC’s work on developing S. neavei guidelines was later incorporated into the revised 2016 WHO onchocerciasis elimination guidelines.33 Post-treatment surveillance (PTS) period After interruption of transmission has been attained and interventions stopped, the focus moves to at least 3 years of PTS activities. Official communication about interruption of transmission and the 3-year PTS period is provided to concerned districts and communities. Surveillance for adult S. neavei or crabs infested with S. neavei aquatic stages during the PTS period in S. neavei foci is continued at intervals deemed adequate for monitoring vector elimination. At the end of the PTS period an OV16 serology survey of children less than 10 years of age is conducted to document that infection rates are <0.1% with 95% statistical confidence. This is in contrast to guidelines for the S. damnosum areas, where WHO PTS recommendations call only for an entomological survey that shows infective rates to be <1/2000 (with 95% confidence) or that ATPs are <20 L3/person/year (L3 is the infective larval stage of the filarial worm of Onchocerca volvulus usually in the blackr fly's head and ready to be transmitted to the next human being during bitting). If these PTS criteria are met, the UOEEAC will recommend that the focus concerned be declared ‘transmission eliminated’ and its population considered free from risk of onchocerciasis. What has been achieved? Current status in 2017 Uganda is closing in on its goal of eliminating river blindness (onchocerciasis) nationwide by 2020. Six foci have been determined to have met the WHO criteria for elimination by successfully completing the 3-year PTS period: Mpamba-Nkusi, Mount Elgon, Itwara and Imaramagambo (in 2016) and Kashoya-Kitomi and Wambabya-Rwamarongo (in 2017) (Figures 4 and 5). An estimated 1 157 303 persons living in these districts are no longer at risk of acquiring onchocerciasis. To our knowledge, this is the largest population ever declared free of onchocerciasis based on the latest WHO guidelines. These six foci now join the Victoria focus in central Uganda, which achieved elimination in the 1970s, where 2 626 544 people were protected from the infection by ground larviciding with DDT to control the vectors of onchocerciasis. Currently a total of about 3 783 847 Ugandans are no longer at risk of acquiring onchocerciasis. Uganda’s accomplishment is evidence that elimination of river blindness may be possible in Africa. Figure 4. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2017. Figure 4. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2017. Figure 5. View largeDownload slide Change in endemic status in foci (n=17) between 2007 and 2017. Figure 5. View largeDownload slide Change in endemic status in foci (n=17) between 2007 and 2017. In August 2017 the West Nile and Wadelai foci were reclassified as ‘transmission interrupted,’ joining the Obongi and Nyamugasani foci. There are three foci (Budongo, Bwindi and Nyagak-Bondo) where interruption of transmission of river blindness is thought to have been achieved. Two of these (Bwindi and Nyagak-Bondo) have cross-border transmission with the DRC and therefore require ascertaining the status of onchocerciasis on the DRC side of the border before declaring transmission interruption in Uganda. Transmission of river blindness continues in only two of Uganda’s original 17 focus areas: the large Madi-Mid North focus (with a population of 1 437 565) and the smaller (population 135 046) Lhubiriha focus (Figure 5). The Madi-Mid North and Lhubiriha foci share a border with the Republic of South Sudan and DRC, respectively. Lessons learned from the campaign to eliminate onchocerciasis from Uganda Failure of annual ivermectin treatment to break transmission in some areas The original approach to the elimination of onchocerciasis transmission in Uganda was to liberally advance from a single annual dose of ivermectin to twice-per-year treatment supplemented with vector control/elimination to accelerate the program toward success by 2020. Twice-per-year was to be used because models predicted that interruption of transmission with an annual treatment program was unachievable in areas with high infection rates.34,41 Although Diawara et al.31 demonstrated entomologically that a single annual dose of ivermectin was able to interrupt transmission in foci in Mali and Senegal, failure of annual treatment after 15–25 years has been documented in several areas.35–40 The important lesson is that a single annual dose of ivermectin administered with adequate coverage may not break transmission if the force of transmission is high.38–40 Uganda’s overarching support for a ‘flexible policy’ allowed for annual treatment to continue where sufficient progress could be documented. Lymphatic filariasis (LF) co-endemicity A number of foci where the national guidelines indicated that ivermectin MDA could be halted could not do so because of co-endemicity with LF. In such foci, the UOEEAC recommended that transmission interruption be declared but that the 3-year PTS period would not begin until LF MDA interventions (with ivermectin and albendazole) were discontinued. Examples of this situation include the Maracha-Terego, West Nile and Wadelai foci (Table 1). Wadelai is a particularly telling example, where onchocerciasis transmission was declared interrupted in 2010 but the PTS period did not begin until 7 years later (2017) when LF MDA was finally halted. Other onchocerciasis–LF co-endemic foci that are likely to encounter this challenge of coordinated PTS are the Nyagak-Bondo and Madi-Mid North foci. The presence of the Ministry of Health LF focal person as a participant (observer status) at the UOEEAC has been particularly important for reporting the status of the LF initiative to allow PTS coordination of the two programs. Table 1. Progress of onchocerciasis elimination in Uganda Focus  Interventions  Transmission  PTS  LF co-endemicity  Cross-border transmission  Annual treatment  Bi-annual treatment  Vector elimination/control  Year declared  Status  Victoria Nile  No provided  Not provided  Vector elimination (1950–1977)  1973  Eliminated  No information  No  No  Itwara  1991–2011  Not provided  Vector elimination (1993–2003)  2016  Eliminated  2012–2015  No  No  Mpamba-Nkusi  1997–2006  2007–2012  Vector elimination (2003–2007)  2016  Eliminated  2013–2016  No  No  Imaramagambo  1991–2012  Not provided  No vector control/elimination activities  2016  Eliminated  2013–2016  No  No  Mount Elgon  1994–2006  2007–2011  Vector elimination (2007–2009)  2016  Eliminated  2012–2015  No  No  Kashoya-Kitomi  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Wambabya-Rwamarongo  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Nyamugasani  1993–2015  Not provided  No vector control/elimination activities  2015  Interrupted  2016–2019  No  No  Maracha-Terego  1993–2012  Not provided  No vector control/elimination activities  2014  Interrupted  Not yet  Yes  No  Obongi  1993–2014  Not provided  No vector control/elimination activities  2014  Interrupted  2016–2019  No  No  Wadelai  1993–2005  2006–2010  No vector control/elimination activities  2014  Interrupted  2017–2020  No  No  West Nile  1993–2016  Not provided  No Vector control/elimination activities  2017  Interrupted  2017–2020  No  No  Nyagak-Bondo  1993–2011  2012–present  Vector elimination (2012–2013)  2014  Interruption suspected  Not yet  Yes  Yes  Bwindi  1993–2006  2007–present  No vector Control/elimination activities  2013  Interruption suspected  Not yet  No  Yes  Budongo  1990–2006  2012–present  Vector elimination (2012–2014)  2014  Interruption suspected  Not yet  No  No  Lhubiriha  1993–2014  2015–present  Vector control (2014–present)  Not applicable  Ongoing  Not yet  No  Yes  Madi-Mid North  1994–2011  2012–present  Vector control (2012–present)  Not applicable  Ongoing  Not yet  Yes  Yes  Focus  Interventions  Transmission  PTS  LF co-endemicity  Cross-border transmission  Annual treatment  Bi-annual treatment  Vector elimination/control  Year declared  Status  Victoria Nile  No provided  Not provided  Vector elimination (1950–1977)  1973  Eliminated  No information  No  No  Itwara  1991–2011  Not provided  Vector elimination (1993–2003)  2016  Eliminated  2012–2015  No  No  Mpamba-Nkusi  1997–2006  2007–2012  Vector elimination (2003–2007)  2016  Eliminated  2013–2016  No  No  Imaramagambo  1991–2012  Not provided  No vector control/elimination activities  2016  Eliminated  2013–2016  No  No  Mount Elgon  1994–2006  2007–2011  Vector elimination (2007–2009)  2016  Eliminated  2012–2015  No  No  Kashoya-Kitomi  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Wambabya-Rwamarongo  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Nyamugasani  1993–2015  Not provided  No vector control/elimination activities  2015  Interrupted  2016–2019  No  No  Maracha-Terego  1993–2012  Not provided  No vector control/elimination activities  2014  Interrupted  Not yet  Yes  No  Obongi  1993–2014  Not provided  No vector control/elimination activities  2014  Interrupted  2016–2019  No  No  Wadelai  1993–2005  2006–2010  No vector control/elimination activities  2014  Interrupted  2017–2020  No  No  West Nile  1993–2016  Not provided  No Vector control/elimination activities  2017  Interrupted  2017–2020  No  No  Nyagak-Bondo  1993–2011  2012–present  Vector elimination (2012–2013)  2014  Interruption suspected  Not yet  Yes  Yes  Bwindi  1993–2006  2007–present  No vector Control/elimination activities  2013  Interruption suspected  Not yet  No  Yes  Budongo  1990–2006  2012–present  Vector elimination (2012–2014)  2014  Interruption suspected  Not yet  No  No  Lhubiriha  1993–2014  2015–present  Vector control (2014–present)  Not applicable  Ongoing  Not yet  No  Yes  Madi-Mid North  1994–2011  2012–present  Vector control (2012–present)  Not applicable  Ongoing  Not yet  Yes  Yes  Coordination with the LF program has implications for finances, personnel and time given the need for extended monitoring of entomological indicators stipulated in guidelines. It should be noted that while the current WHO onchocerciasis guidelines require that onchocerciasis PTS can only begin after MDA for LF has stopped, the reciprocal situation is not found in LF operating procedures; for example, post-MDA LF surveillance may launch without regard to ongoing onchocerciasis ivermectin monotherapy MDA since the WHO recommended LF treatment is combined therapy. Cross-border transmission Uganda has possible cross-border transmission with the DRC in the Bwindi, Lhubiriha and Nyagak-Bondo foci as well as with the Republic of South Sudan (RSS) in the Madi-Mid North focus (Table 1). The WHO guidelines will not allow these Uganda foci to be declared as transmission interrupted or eliminated until the extent of these cross-border transmission zones and the status of onchocerciasis elimination efforts on the other side of the border are known. The Ministry of Health in Uganda has recently established effective coordination with its sister Ministry of Health in the DRC that resulted in joint 2016 epidemiological and entomological surveys in border areas. Discussions have also begun with health officials in the RSS to develop similar surveys and other coordinated activities. The Carter Center and Sightsavers have been assisting these activities. Ideally, coordinated joint implementation efforts will soon be carried out in order to interrupt transmission in these shared onchocerciasis foci. However, such shared activities must take into account the security problems in the DRC areas bordering the Bwindi and Lhubiriha foci and in the RSS adjacent to the Madi-Mid North focus. People from the DRC and RSS who cross into Uganda as refugees are highly mobile, moving back and forth between Uganda and their respective countries as the situation dictates. Uganda has made every effort to treat the refugees with ivermectin, but obtaining adequate treatment coverage among these highly mobile populations will be a challenge. Advantages of a national molecular laboratory The presence of a national laboratory avoids the bureaucracy associated with the export of samples and provides timely access to the results by the UOEP and UOEEAC. The personnel in the laboratory are program staff and their workflow is based on priorities set by the UOEEAC. The UOEEAC has recommended that PCR pool screening be used in analysing flies rather than dissections, because of the risk of confusing larvae of Onchocerca (especially O. ochengi).40 The annual cost of laboratory operations is about $35 000 to $40 000. The effect of environmental changes In some foci the vectors have disappeared, presumably the result of environmental changes. The absence of S. neavei is presumed to be due to the disappearance of the freshwater crabs essential for the development of its aquatic stages. This is possibly due to deforestation.42,43 In the Wadelai focus where S. damnosum was presumed to have been the vector, no flies have been captured in recent years, yet no larviciding was ever done and there has been no noticeable change in the Ora and Aroga rivers.43 Also, no vectors have been captured in the (presumed) S. damnosum Obongi focus. It is hypothesized that vector disappearance there was due to poor agricultural practices that increased soil erosion and siltation of vector breeding tributaries flowing into the Nile River. In the Imaramagambo focus, the disappearance of the vector could have been due to runoff into rivers of agricultural chemicals used intensively on the nearby tea plantations.29 Effective communication with communities when stopping MDA and throughout the PTS period A carefully designed communication strategy is needed to explain to communities why MDA is being withdrawn, and these communications should continue throughout the PTS period. In Guatemala, the Knowledge, Attitudes and Practices (KAP) questionnaire surveys in the foci where onchocerciasis was eliminated showed that many persons still want ivermectin and more than a half did not believe that onchocerciasis had been eliminated.44 Our recent KAP experience in Uganda (unpublished) has shown the same attitudes among the people in foci where onchocerciasis has been eliminated. The importance of the UOEEAC in advising WHO guidelines The basis for declaring elimination of onchocerciasis transmission in every Ugandan focus is being meticulously documented and archived so that it can ultimately be made available to the external WHO verification team. To enhance the quality and acceptability of the data, the UOEEAC has worked with Ministry of Health staff to publish the elimination history of each focus in peer-reviewed medical literature. In this way, it is hoped that the quality of the data placed in the national onchocerciasis elimination dossier for Uganda will be incontrovertible.41 Conclusion When Uganda declared an objective of nationwide onchocerciasis elimination by 2020, the tempo of activities accelerated dramatically. Treatment coverage improved under the twice-yearly ivermectin treatment and ground-based larviciding accelerated the interruption of transmission. The new energy motivated targeted communities and was instrumental in keeping health workers focused and interested. The establishment of an independent technical advisory committee, the availability of sensitive and highly specific diagnostic tools at a national laboratory and the obvious annual progress in moving foci along the pathway to elimination are other reasons for the rapid progress towards nationwide onchocerciasis elimination. The main challenge remains cross-border issues with the DRC and RSS, yet the 2020 target for nationwide elimination of onchocerciasis remains within reach. Authors' contributions: As the main author, MNK drafted the manuscript, and all the authors (MNK, TL, PH, TRU, RG, LH, EB, AK, JN, ET and FR) reviewed the manuscript, read and approved the final version. Acknowledgements: We thank and acknowledge all health workers at the district and national levels, the UOEEAC members and the affected communities for their hard work. The late Dr Brian Duke and Dr Frank Walsh (first chair of the UOEEAC), who re-established the Uganda Onchocerciasis Control Program and later persuaded Uganda to take a leadership role in advancing onchocerciasis elimination in Africa, are highly acknowledged. The program could not have succeeded without support from the RBF, CBM, East Ankole Diocese and association of volunteers in international services with Hq in Italy during early 1990s. GTZ and the Bernhard Nocht Institute for Tropical Medicine (Hamburg, Germany) are highly appreciated for supporting a study in 1990 on whether the organophosphate temephos could be safely used to control/eliminate S. neavei, a vector for onchocerciasis in the Kabarole District. The program could not have succeeded in the shift from control to elimination without support from Sightsavers, The Carter Center, John Moores, the LCIF, the Lions Clubs of Uganda, MSD, the Mectizan Donation Program and US Agency for International Development’s ENVISION Project, led by RTI International. We also thank the WHO/African Program for Onchocerciasis Control, WHO Geneva and the Uganda WHO office. Progress towards elimination could not have succeeded if the Uganda Ministry of Health had not provided enabling policies, personnel, office space, laboratory accommodation, and the mechanisms for timely and effective decision-making mechanisms that have kept the program focused and successful. Funding: None. Competing interests: Not required. Ethical approval: Not required. References 1 Barnley GR. Onchocerciasis. Uganda atlas of disease distribution . Nairobi, Kenya: East African Publishing; 1975, p. 38– 40. 2 Raper AB, Lapkin RG. Endemic dwarfism in Uganda. East Afr Med J  1950; 27: 1– 2. 3 Nelson GS. Hanging groin and hernia complications of onchocerciasis. Trans R Soc Trop Med Hyg  1958; 52: 272– 5. Google Scholar CrossRef Search ADS PubMed  4 Colebunders R, Post R, O’Neill S et al.  . Nodding syndrome since 2012: recent progress, challenges and recommendations for future research. Trop Med Int Health  2015; 20( 2): 194– 200. Google Scholar CrossRef Search ADS PubMed  5 Barnley GR. Geographical distribution and incidence of onchocerciasis in Uganda—Geographical distribution of onchocercal eye lesions in Uganda—Transmission potential of Simulium vectors of onchocerciasis in Uganda. WHO second conference on onchocerciasis, Brazzaville, 12–17 June 1961. AFR/Onchocerciasis (1961)/2 (mimeograph). 6 Sasa M. Human filariasis: a global survey of epidemiology and control . Tokyo: University of Tokyo Press; 1976, p. 313– 5. 7 Mpagi J, Katamanywa J, Garms R. Dispersal range of Simulium neavei in an onchocerciasis focus of western Uganda. Med Vet Entomol  2000; 14(1): 95– 9. Google Scholar CrossRef Search ADS   8 Barnley GR, Prentice MA. Simulium neavei in Uganda. East Afr Med J  1958; 35: 475– 85. 9 Barnley GR. Onchocerciasis in Kigezi District, Uganda. East Afr Med J  1949; 26: 308– 10. 10 van de Werd HJ. Onchocerciasis near Lake George, Uganda. Trop Geogr Med  1973; 25: 307– 8. Google Scholar PubMed  11 Barnley GR. Control of Simulium vectors of onchocerciasis in Uganda. Proceedings of the 10th International Congress of Entomology, Montreal, August 17–25, 1956. 12 Brown WA. A survey of Simulium control in Africa. Bull World Health Org  1962; 27(4–5): 511– 27. 13 Prentice MA. Economical local control measures against Simulium neavei, a vector of onchocerciasis in the Budongo Forest, Uganda. Proc 7th Int Congr Trop Med Mal Rio de Janeiro  1963; 2: 142– 3. 14 Prentice MA (ed.). Simulium control program in Uganda. Research and Control of Onchocerciasis in the Western Hemisphere: Proceedings of an International Symposium, Washington, DC, 18–21 November 1974, 87–93. 15 Colbourne MJ, Crosskey RW. Onchocerciasis and its control in Uganda . AFR/Oncho/8 Rev. 1/ WHO/Oncho/30.65/ Rev.1. Geneva: World Health Organization; 1965. 16 Ngoumou P, Walsh JF, Mace JM. A rapid mapping technique for the prevalence and distribution of onchocerciasis: a Cameroon case study. Ann Trop Med Parasitol  1994; 88(5): 463– 74. Google Scholar CrossRef Search ADS   17 Katabarwa M, Onapa AW, Nakileza B. Rapid epidemiological mapping of onchocerciasis in areas of Uganda where Simulium neavei is the vector. East Afr Med J  1999; 76(8): 440– 6. 18 Mutabazi D, Duke BO. Onchocerciasis control in Uganda: how can self-sustaining, community-based treatment with ivermectin be achieved? Ann Trop Med Parasitol  1998; 92(2): 195– 203. Google Scholar CrossRef Search ADS   19 Garms R, Lakwo TL, Ndyomugyenyi R et al.  . The elimination of the vector Simulium neavei from the Itwara onchocerciasis focus in Uganda by ground larviciding. Acta Trop  2009; 111(3): 203– 10. Google Scholar CrossRef Search ADS   20 Lakwo TL, Ndyomugyenyi R, Onapa AW et al.  . Transmission of Onchocerca volvulus and prospects for the elimination of its vector, the blackfly Simulium neavei in the Mpamba-Nkusi focus in western Uganda. Med Vet Entomol  2006; 20(1): 93– 101. Google Scholar CrossRef Search ADS   21 Dadzie Y, Neira M, Hopkins D. Final report of the Conference on the Eradicability of Onchocerciasis. Filaria J  2003; 2(1): 2. Google Scholar CrossRef Search ADS   22 Sauerbrey M. The Onchocerciasis Elimination Program for the Americas (OEPA). Ann Trop Med Parasitol  2008; 102(Suppl 1): 25– 9. Google Scholar CrossRef Search ADS PubMed  23 Cupp EW, Cupp MS. 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  2005; 73(6): 1159– 61. 24 Katabarwa MN, Walsh F, Habomugisha P et al.  . Transmission of onchocerciasis in Wadelai focus of northwestern Uganda has been interrupted and the disease eliminated. J Parasitol Res  2012; 2012: 748540. Google Scholar CrossRef Search ADS PubMed  25 Ndyomugyenyi R, Tukesiga E, Büttner DW et al.  . The impact of ivermectin treatment alone and when in parallel with Simulium neavei elimination on onchocerciasis in Uganda. Trop Med Int Health  2004; 9(8): 882– 6. Google Scholar CrossRef Search ADS   26 Oguttu D, Byamukama E, Katholi CR et al.  . Serosurveillance to monitor onchocerciasis elimination: the Ugandan experience. Am J Trop Med Hyg  2014; 90(2): 339– 45. Google Scholar CrossRef Search ADS   27 Guidelines for certification of onchocerciasis elimination in Uganda . Kampala, Uganda: Uganda Ministry of Health; 2011. 28 Katabarwa M, Lakwo T, Habomugisha P et al.  . Transmission of Onchocerca volvulus by Simulium neavei in Mount Elgon focus of eastern Uganda has been interrupted. Am J Trop Med Hyg  2014; 90(6): 1159– 66. Google Scholar CrossRef Search ADS   29 Katabarwa MN, Katamanywa J, Lakwo T et al.  . The Imaramagambo onchocerciasis focus in southwestern Uganda: interruption of transmission after disappearance of the vector Simulium neavei and its associated freshwater crabs. Am J Trop Med Hyg  2016; 95(2): 417– 25. Google Scholar CrossRef Search ADS   30 World Health Organization. Certification of elimination of human onchocerciasis: criteria and procedures. WHO/CDS/CPE/CEE/2001.18b. Geneva: World Health Organization; 2001. http://whqlibdoc.who.int/hq/2001/WHO_CDS_CPE_CEE_2001.18b.pdf. 31 Diawara L, Traore, MO, Badji A et al.  . Feasibility of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: first evidence from studies in Mali and Senegal. PLoS Negl Trop Dis  2009; 3(7): e497. Google Scholar CrossRef Search ADS   32 Traore MO, Sarr MD, Badji A et al.  . Proof-of-principle of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: final results of a study in Mali and Senegal. PLoS Negl Trop Dis  2012; 6(9): e1825. Google Scholar CrossRef Search ADS   33 World Health Organization. Guidelines for stopping mass drug administration and verifying elimination of human onchocerciasis. Criteria and procedures. Geneva: World Health Organization; 2016. 34 Duerr HP, Eichner M. Epidemiology and control of onchocerciasis: the threshold-biting rate of savannah onchocerciasis in Africa. Int J Parasitol  2010; 40(6): 641– 50. Google Scholar CrossRef Search ADS   35 Ndyomugyenyi R, Lakwo T, Habomugisha P et al.  . Progress towards the elimination of onchocerciasis as a public-health problem in Uganda: opportunities, challenges and the way forward. Ann Trop Med Parasitol  2007; 101(4): 323– 33. Google Scholar CrossRef Search ADS   36 Katabarwa MN, Eyamba A, Nwane P et al.  . Seventeen years of annual distribution of ivermectin has not interrupted onchocerciasis transmission in North Region, Cameroon. Am J Trop Med Hyg  2011; 85(6): 1041– 49. Google Scholar CrossRef Search ADS   37 Katabarwa MN, Eyamba A, Nwane P et al.  . Fifteen years of annual mass treatment of onchocerciasis with ivermectin have not interrupted transmission in the West Region of Cameroon. J Parasitol Res  2013; 2013: 420928. Google Scholar CrossRef Search ADS PubMed  38 Katabarwa MN, Lakwo T, Habomugisha P et al.  . Transmission of Onchocerca volvulus continues in Nyagak-Bondo focus of northwestern Uganda after 18 years of a single dose of annual treatment with ivermectin. Am J Trop Med Hyg  2013; 89(2): 293– 300. Google Scholar CrossRef Search ADS   39 Yaya G, Kobangué L, Kémata B et al.  . [ Elimination or control of the onchocerciasis in Africa? Case of Gami village in Central African Republic] (in French). Bull Soc Pathol Exot  2016; 107(3): 188– 93. 40 Eisenbarth A, Achukwi MD, Renz A. Ongoing transmission of Onchocerca volvulus after 25 years of annual ivermectin mass treatments in the Vina du Nord River Valley, in North Cameroon. PLoS Negl Trop Dis  2016; 10(2): e0004392. Google Scholar CrossRef Search ADS   41 Winnen M, Plaisier AP, Alley ES et al.  . Can ivermectin mass treatments eliminate onchocerciasis in Africa? Bull World Health Org  2002; 80(5): 384– 91. 42 Fischer P, Garms R, Buttner DW et al.  . Reduced prevalence of onchocerciasis in Uganda following either deforestation or vector control with DDT. East Afr Med J  1997; 74(5): 321– 5. 43 Katabarwa MN, Walsh F, Habomugisha P et al.  . Transmission of onchocerciasis in Wadelai focus of northwestern Uganda has been interrupted and the disease eliminated. J Parasitol Res  2012; 2012: 748540. Google Scholar CrossRef Search ADS PubMed  44 Richards FO Jr, Klein RE, de León O et al.  . A knowledge, attitudes and practices survey conducted three years after halting ivermectin mass treatment for onchocerciasis in Guatemala. PLoS Negl Trop Dis  2016; 10(6): e0004777. Google Scholar CrossRef Search ADS   © The Author(s) 2018. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Health Oxford University Press

After 70 years of fighting an age-old scourge, onchocerciasis in Uganda, the end is in sight

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Abstract

Abstract Onchocerciasis causes severe itching, serious skin disease and ocular damage leading to visual impairment or permanent blindness. It is associated with hanging groin, epilepsy, Nakalanga dwarfism and, most recently, nodding disease. This disease affected communities in 17 transmission foci in 37 districts of Uganda, where about 6.7 million people are once at risk. The efforts against onchocerciasis in Uganda commenced in the late 1940s, when vector control was launched using dichlorodiphenyltrichloroethane; by 1973, Simulium damnosum had been eliminated in the Victoria focus. Success outside of the Victoria focus was short-lived due to changes in government priorities and the political upheavals of the 1970s and 1980s. With the return of political stability, annual treatment with ivermectin through mass drug administration was launched in the early 1990s. Control of the disease has been successful, but there has been failure in interrupting transmission after more than 15 years. In 2007 Uganda launched a nationwide transmission elimination policy based on twice-per-year treatment and vector control/elimination, with a goal of eliminating river blindness nationwide by 2020. By 2017, 1 157 303 people from six foci had been freed from river blindness. This is the largest population ever declared free under World Health Organization elimination guidelines, providing evidence that elimination of river blindness in Africa is possible. Onchocerciasis, Control, Elimination, Larvicide, Ivermectin Introduction Human onchocerciasis is caused by the filarial nematode Onchocerca volvulus, which is transmitted by the bites of Simulium flies that breed in fast-flowing rivers, hence its common name in Africa, ‘river blindness.’ Unlike in West Africa, onchocerciasis is a highly focal disease in East and Central Africa, Yemen and the Americas. The disease can cause severe itching, skin lesions and eyesight impairment, and can lead to permanent blindness when not treated.1 It has been hypothesized that onchocerciasis is responsible for a condition known as ‘Nakalanga syndrome,’ a form of dwarfism that is observed in some parts of Uganda with high onchocerciasis prevalence rates,2,3 and has been associated with epilepsy and ‘nodding syndrome.’4 In addition, ‘hanging groin’ and hernia are also known complications of the disease. Early history of onchocerciasis in Uganda In the late 1950s it was estimated that at least 1.18 million people out of a total population of 6.5 million living in Uganda were at risk of being infected with onchocerciasis.5 About 40% (472 000) of the at-risk population were estimated to be infected with onchocerciasis. In Uganda, the vectors of onchocerciasis include Simulium neavei, which develops in a phoretic association with freshwater crabs, and members of the Simulium damnosum complex.5 It is known that S. damnosum thrives at low altitudes and in warm, open, fast-running rivers and streams. S. damnosum has a long flight range of 45 to 65 km from its breeding sites and does not need corridors of bush for protection.6 In contrast, S. neavei requires a closed canopy that provides shade to migrate and tends to breed at a higher altitude than S. damnosum. S. neavei is usually found in moist, cool, green forests, as well as riverine fringing forest environments. Their flight range of less than 6 km is much less than S. damnosum.7 The main historical habitats for S. damnosum s.l. in Uganda during the 1950s were the Victoria Nile River, where Christy originally described S. damnosum, with almost 100% of the inhabitants afflicted with onchocerciasis; the Murchison Nile from the Atura River ending in Murchison Falls; and the Rwenzori focus that extended into the Democratic Republic of the Congo (DRC), with a prevalence of onchocerciasis ranging from 54 to 91%.6 Onchocerciasis transmitted by S. neavei was originally reported in the following areas of Uganda: Budongo Forest, where the baseline skin microfilaria (mf) rate for sawmill workers was 78%, and 46% among students in the forestry college8; Mount Elgon, where the baseline mf prevalence rate was 80%; West Nile, where the mf prevalence rate was 56%3; and Kigezi (now known as the Bwindi focus), where the prevalence rate was 80%9 (Figure 1). In 1973 a new onchocerciasis focus east and southeast of Lake George (now designated the Kashoya-Kitomi focus) was reported, but no prevalence rate was provided.10 Figure 1. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 1975.1 Figure 1. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 1975.1 Control of onchocerciasis (1950–1973) Previously, dichlorodiphenyltrichloroethane (DDT) was widely used for onchocerciasis control in Uganda. Successful intermittent control efforts in the Victoria Nile focus on the Nile River commenced in 1952.11,12 This resulted in S. damnosum elimination along a 70 km stretch of the Nile River between Lake Victoria and Lake Kyoga by 1973. In 1974, after a military coup, all the expatriate leaders of national vector control activities were forced to leave Uganda and further monitoring of the Victoria Nile focus was halted; however, activities by the Vector Control Division of the Ministry of Health continued there until 1977. In the Murchison Nile focus, a trial of DDT vector control of S. damnosum was attempted in 1959 to protect workers constructing a hydroelectric power station. After that trial a reinvasion by S. damnosum from Atura on the Murchison Nile was documented.13 In 1971, DDT larviciding was extended to cover the whole Rwenzori focus.13 In the Budongo S. neavei focus, the vector was nearly eliminated by 1962.14,15 Mass drug administration (MDA) with diethylcarbamazine citrate (DEC) was also provided.15 In the Mount Elgon focus, vector control was initiated in 1957, and in 1972 the prevalence was determined to have dropped to 5–10%. Vector control was also piloted in the West Nile focus in 1955.3 In the Kigezi onchocerciasis endemic area, DEC was provided to patients at health facilities until 1992, when the program introduced ivermectin through community-based MDA programs. There is no evidence that any vector control or MDA was carried out in the Kashoya-Kitomi onchocerciasis focus during this period. Re-establishment of the national onchocerciasis control program (1987–2006) In 1987, MSD, also known as Merck & Co., Inc., Kenilworth, NJ, USA, committed to donating ivermectin (Mectizan) ‘as long as necessary’ for the control of onchocerciasis, an event that coincided with the return of peace to Uganda. In 1989, the Uganda Foundation for the Blind, with Sightsavers’ funding, began mass treatment with ivermectin in the Budongo onchocerciasis focus. Treatment with ivermectin followed in the Itwara onchocerciasis focus of western Uganda in the Kabarole and Kyejonjo districts, with assistance from the German Technical Cooperation Agency (GTZ). However, it was not until mid-1992 that a comprehensive and systematic nationwide program was established, led by the Uganda Ministry of Health with support from the River Blindness Foundation (RBF). The Maracha-Terego focus in Maracha and Terego counties and the West Nile focus in the Maracha-Terego, Koboko and Yumbe districts provided treatment from 1993 to 1996, supported by the Christoffel Blinden Mission (CBM). Apart from northern Uganda, most onchocerciasis endemic areas were mapped during early and mid-1990s with support from the RBF and the United Nations Children’s Fund, United Nations Development Programme, World Bank and World Health Organization (WHO) Program for Research and Training in Tropical Disease Research (TDR). A nationwide rapid epidemiological mapping of onchocerciasis (REMO) based on rapid epidemiological assessment with nodule palpation in S. damnosum and S. neavei areas was conducted between 1993 and 1997 (Figure 2).16,17 In 1996, The Carter Center assumed responsibility for the RBF and later in the year a partnership program known as the African Programme for Onchocerciasis Control (APOC) was launched with World Bank trust funds and the WHO as its executing agency. By 1996 the Uganda Onchocerciasis Control Programme had received financial support from the APOC, Sightsavers (the Bulisa, Hoima and Masindi districts) and The Carter Center (assisting the other endemic districts in the country).18 Figure 2. View largeDownload slide REMO map of Uganda showing the status of onchocerciasis in 1996. Figure 2. View largeDownload slide REMO map of Uganda showing the status of onchocerciasis in 1996. Comprehensive assistance for community-directed treatment with ivermectin (CDTI) from the APOC was provided for 5 years. Afterwards, APOC financial support was more limited and focused on replacement of capital equipment and advocacy. The goal of the APOC and Uganda at the time was to control the disease as a public health problem by limiting the morbidity arising from the disease, thereby fostering economic development. The control approach was not expected to interrupt transmission of the infection, with the exception of two S. neavei foci (Mpamba-Nkusi and Itwara), where the APOC supported ground larviciding for vector elimination activities. These two foci made considerable progress, proving the durability of localized vector elimination in S. neavei areas after 2–3 years of larviciding.19,20 Inspiration from the Americas Uganda policymakers were concerned that the country, with more than 50 years of sporadic onchocerciasis control activities, could not continue with business as usual. With the return of peace and political stability nationwide, the government of Uganda was keen to break the legacy of onchocerciasis, interrupt its transmission and achieve national elimination. Noting that the 2001 Conference on Eradicability of Onchocerciasis at The Carter Center indicated the feasibility of onchocerciasis elimination in the Americas,21,22 Ugandan policymakers began to study the Onchocerciasis Elimination Program for the Americas (OEPA) twice-per-year treatment policy. In particular, rethinking onchocerciasis elimination gained traction with the publication of a report by Cupp and Cupp.23 In this report, data analysis from the Americas concluded that twice-per-year ivermectin MDA achieving ≥85% eligible population coverage reduced the lifespan of adult O. volvulus, leading to their demise within 6.5 years. A pilot onchocerciasis elimination project using twice-yearly ivermectin treatment in the Wadelai focus of Uganda conducted in 2005–2006 found that CDTI could attain a treatment coverage of at least 90% of the eligible population in both rounds.24 At the same time, a combination of vector control and ivermectin treatment in some foci was found to be an effective approach for rapid transmission interruption.25 In 2006, a delegation from the Ministry of Health of Uganda travelled to Guatemala to attend the Inter-American Conference on Onchocerciasis (IACO). While attending the IACO meeting, the Uganda delegation visited the Universidad del Valle de Guatemala/Centers for Disease Control laboratory that was providing laboratory-based molecular testing to verify progress towards elimination for OEPA. They learned about lab training and equipment requirements for conducting enzyme-linked immunosorbent assay (ELISA) tests for detecting IgG4 antibodies to the OV16 recombinant antigen and vector pool screening for O. volvulus DNA using the O-150 polymerase chain reaction (PCR).26 Energized by their visit, the delegates returned home determined to undertake a nationwide elimination effort in Uganda. A national elimination policy (2007–2016) The Uganda Ministry of Health crafted a new policy for nationwide onchocerciasis transmission elimination that was launched by the president of Uganda, His Excellency, Yoweri Museveni, at a national meeting held in Kampala in January 2007. The renamed Uganda Onchocerciasis Elimination Program (UOEP) had several charges. First, it was no longer business as usual, and all tools (ivermectin and vector control) were to be used in combination when and where necessary. Twice-per-year ivermectin treatment was to be the norm except in areas where once-per-year had been clearly effective in breaking transmission. Second, a molecular laboratory based on the Guatemala model was established to help monitor progress towards elimination. Third, an independent technical advisory committee, the Uganda Onchocerciasis Elimination Expert Advisory Committee (UOEEAC), was established to help the ministry progress towards nationwide elimination. Key assisting partners (The Carter Center, Lion Clubs of Uganda and Lion Clubs International Foundation [LCIF], Mectizan Donation Program and Sightsavers) would have seats on the UOEEAC. The UOEP and UOEEAC embarked on the following: Refining the onchocerciasis map and launching twice-per-year treatment The UOEP aggressively embarked on refining and completing the onchocerciasis map of Uganda in order to include any hypoendemic communities that may have been left untreated. Vector elimination was achieved in the Victoria focus and (likely) in the Itwara and Mpamba-Nkusi foci in 2007 (Figure 3). A population of 4.9 million people living in 37 districts were still at risk of onchocerciasis in 16 foci (not counting Victoria) and transmission interruption appeared to have been reached in the Nyamugasani, Maracha-Terego, Obongi, Imaramagambo, Itwara and West Nile foci. Twice-per-year treatment with ivermectin through CDTI continued in Wadelai and was launched in the Budongo, Bwindi, Kashoya-Kitomi, Mount Elgon and Mpamba-Nkusi foci in 2007, Wambabya-Rwamarongo in 2008 and later in Nyagak-Bondo (2012), Madi-Mid North (2013) and Lhubiriha (2015). Figure 3. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2007. Figure 3. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2007. Establishment of the molecular laboratory In 2008 the Ministry of Health provided space for the UOEP’s molecular laboratory at the Vector Control Division as well as personnel to run it. The Carter Center provided equipment and financial support to the laboratory and the University of South Florida laboratory trained the Uganda laboratory personnel. The new laboratory has allowed close monitoring of the impact of interventions on onchocerciasis transmission. Its experience, the largest operation among onchocerciasis molecular laboratories in Africa, has been published.26 By mid-2016 it had analysed more than 65 000 blood spot samples with the OV16 ELISA, as well as thousands of Simulium flies and skin snips from some foci using the O-150 PCR. The University of South Florida continues to ensure acceptable quality control standards. Uganda Onchocerciasis Elimination Expert Advisory Committee The UOEEAC held its first meeting in 2008. Its membership is comprised of the Ministry of Health (including representatives from district health services), non-governmental development organization partners and independent national and international experts on the disease. The WHO and Mectizan Donation Program representatives are usually in attendance as observers.27–29 The UOEEAC provides technical advice to the UOEP through review, monitoring and evaluation of each of the 17 foci and recommends effective approaches and methods for hastening onchocerciasis elimination. The UOEEAC also reviews strategic guidelines from various onchocerciasis global or regional technical committees and vets them from the Ugandan perspective. It meets once a year in Kampala, Uganda. The UOEEAC is charged with the provision of credible, independent and cutting-edge technical advice to help Uganda eliminate onchocerciasis by 2020. Second, the expert technical committee is entrusted with the responsibility of providing evidence-based recommendations on the progress of interruption of onchocerciasis transmission to the Ministry of Health for timely decision making. Recommendations from the UOEEAC flow to the National Certification Committee, a technical committee established in the hierarchy of the Ministry of Health structure. National criteria for determining the elimination of onchocerciasis in Uganda The first assignment of the UOEEAC was to formulate national guidelines for determining elimination in Uganda. The committee worked to synthesize two different sets of elimination criteria: those based on the 2001 WHO criteria for onchocerciasis elimination30 and those put forward by the APOC/TDR, as described by Diawara et al.31 and Traore et al.32 The UOEEAC drafted the national guidelines and the Ministry of Health reviewed and accepted them in 2011.27 In its review of the WHO and APOC guidelines the UOEEAC noted a lack of entomological indicators for S. neavei areas where elimination of the vector had been achieved. Thus the UOEEAC developed totally new guidelines that used crab collections as one of the principal monitoring elements. The UOEEAC defined S. neavei elimination indicators as a lack of positive crabs for larvae/pupae of S. neavei species in a series of surveys and the absence of adult flies collected in a defined focus over a period of 3 years implies interruption of transmission of onchocerciasis.27,29 The UOEEAC’s work on developing S. neavei guidelines was later incorporated into the revised 2016 WHO onchocerciasis elimination guidelines.33 Post-treatment surveillance (PTS) period After interruption of transmission has been attained and interventions stopped, the focus moves to at least 3 years of PTS activities. Official communication about interruption of transmission and the 3-year PTS period is provided to concerned districts and communities. Surveillance for adult S. neavei or crabs infested with S. neavei aquatic stages during the PTS period in S. neavei foci is continued at intervals deemed adequate for monitoring vector elimination. At the end of the PTS period an OV16 serology survey of children less than 10 years of age is conducted to document that infection rates are <0.1% with 95% statistical confidence. This is in contrast to guidelines for the S. damnosum areas, where WHO PTS recommendations call only for an entomological survey that shows infective rates to be <1/2000 (with 95% confidence) or that ATPs are <20 L3/person/year (L3 is the infective larval stage of the filarial worm of Onchocerca volvulus usually in the blackr fly's head and ready to be transmitted to the next human being during bitting). If these PTS criteria are met, the UOEEAC will recommend that the focus concerned be declared ‘transmission eliminated’ and its population considered free from risk of onchocerciasis. What has been achieved? Current status in 2017 Uganda is closing in on its goal of eliminating river blindness (onchocerciasis) nationwide by 2020. Six foci have been determined to have met the WHO criteria for elimination by successfully completing the 3-year PTS period: Mpamba-Nkusi, Mount Elgon, Itwara and Imaramagambo (in 2016) and Kashoya-Kitomi and Wambabya-Rwamarongo (in 2017) (Figures 4 and 5). An estimated 1 157 303 persons living in these districts are no longer at risk of acquiring onchocerciasis. To our knowledge, this is the largest population ever declared free of onchocerciasis based on the latest WHO guidelines. These six foci now join the Victoria focus in central Uganda, which achieved elimination in the 1970s, where 2 626 544 people were protected from the infection by ground larviciding with DDT to control the vectors of onchocerciasis. Currently a total of about 3 783 847 Ugandans are no longer at risk of acquiring onchocerciasis. Uganda’s accomplishment is evidence that elimination of river blindness may be possible in Africa. Figure 4. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2017. Figure 4. View largeDownload slide Map of Uganda showing the status of onchocerciasis in 2017. Figure 5. View largeDownload slide Change in endemic status in foci (n=17) between 2007 and 2017. Figure 5. View largeDownload slide Change in endemic status in foci (n=17) between 2007 and 2017. In August 2017 the West Nile and Wadelai foci were reclassified as ‘transmission interrupted,’ joining the Obongi and Nyamugasani foci. There are three foci (Budongo, Bwindi and Nyagak-Bondo) where interruption of transmission of river blindness is thought to have been achieved. Two of these (Bwindi and Nyagak-Bondo) have cross-border transmission with the DRC and therefore require ascertaining the status of onchocerciasis on the DRC side of the border before declaring transmission interruption in Uganda. Transmission of river blindness continues in only two of Uganda’s original 17 focus areas: the large Madi-Mid North focus (with a population of 1 437 565) and the smaller (population 135 046) Lhubiriha focus (Figure 5). The Madi-Mid North and Lhubiriha foci share a border with the Republic of South Sudan and DRC, respectively. Lessons learned from the campaign to eliminate onchocerciasis from Uganda Failure of annual ivermectin treatment to break transmission in some areas The original approach to the elimination of onchocerciasis transmission in Uganda was to liberally advance from a single annual dose of ivermectin to twice-per-year treatment supplemented with vector control/elimination to accelerate the program toward success by 2020. Twice-per-year was to be used because models predicted that interruption of transmission with an annual treatment program was unachievable in areas with high infection rates.34,41 Although Diawara et al.31 demonstrated entomologically that a single annual dose of ivermectin was able to interrupt transmission in foci in Mali and Senegal, failure of annual treatment after 15–25 years has been documented in several areas.35–40 The important lesson is that a single annual dose of ivermectin administered with adequate coverage may not break transmission if the force of transmission is high.38–40 Uganda’s overarching support for a ‘flexible policy’ allowed for annual treatment to continue where sufficient progress could be documented. Lymphatic filariasis (LF) co-endemicity A number of foci where the national guidelines indicated that ivermectin MDA could be halted could not do so because of co-endemicity with LF. In such foci, the UOEEAC recommended that transmission interruption be declared but that the 3-year PTS period would not begin until LF MDA interventions (with ivermectin and albendazole) were discontinued. Examples of this situation include the Maracha-Terego, West Nile and Wadelai foci (Table 1). Wadelai is a particularly telling example, where onchocerciasis transmission was declared interrupted in 2010 but the PTS period did not begin until 7 years later (2017) when LF MDA was finally halted. Other onchocerciasis–LF co-endemic foci that are likely to encounter this challenge of coordinated PTS are the Nyagak-Bondo and Madi-Mid North foci. The presence of the Ministry of Health LF focal person as a participant (observer status) at the UOEEAC has been particularly important for reporting the status of the LF initiative to allow PTS coordination of the two programs. Table 1. Progress of onchocerciasis elimination in Uganda Focus  Interventions  Transmission  PTS  LF co-endemicity  Cross-border transmission  Annual treatment  Bi-annual treatment  Vector elimination/control  Year declared  Status  Victoria Nile  No provided  Not provided  Vector elimination (1950–1977)  1973  Eliminated  No information  No  No  Itwara  1991–2011  Not provided  Vector elimination (1993–2003)  2016  Eliminated  2012–2015  No  No  Mpamba-Nkusi  1997–2006  2007–2012  Vector elimination (2003–2007)  2016  Eliminated  2013–2016  No  No  Imaramagambo  1991–2012  Not provided  No vector control/elimination activities  2016  Eliminated  2013–2016  No  No  Mount Elgon  1994–2006  2007–2011  Vector elimination (2007–2009)  2016  Eliminated  2012–2015  No  No  Kashoya-Kitomi  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Wambabya-Rwamarongo  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Nyamugasani  1993–2015  Not provided  No vector control/elimination activities  2015  Interrupted  2016–2019  No  No  Maracha-Terego  1993–2012  Not provided  No vector control/elimination activities  2014  Interrupted  Not yet  Yes  No  Obongi  1993–2014  Not provided  No vector control/elimination activities  2014  Interrupted  2016–2019  No  No  Wadelai  1993–2005  2006–2010  No vector control/elimination activities  2014  Interrupted  2017–2020  No  No  West Nile  1993–2016  Not provided  No Vector control/elimination activities  2017  Interrupted  2017–2020  No  No  Nyagak-Bondo  1993–2011  2012–present  Vector elimination (2012–2013)  2014  Interruption suspected  Not yet  Yes  Yes  Bwindi  1993–2006  2007–present  No vector Control/elimination activities  2013  Interruption suspected  Not yet  No  Yes  Budongo  1990–2006  2012–present  Vector elimination (2012–2014)  2014  Interruption suspected  Not yet  No  No  Lhubiriha  1993–2014  2015–present  Vector control (2014–present)  Not applicable  Ongoing  Not yet  No  Yes  Madi-Mid North  1994–2011  2012–present  Vector control (2012–present)  Not applicable  Ongoing  Not yet  Yes  Yes  Focus  Interventions  Transmission  PTS  LF co-endemicity  Cross-border transmission  Annual treatment  Bi-annual treatment  Vector elimination/control  Year declared  Status  Victoria Nile  No provided  Not provided  Vector elimination (1950–1977)  1973  Eliminated  No information  No  No  Itwara  1991–2011  Not provided  Vector elimination (1993–2003)  2016  Eliminated  2012–2015  No  No  Mpamba-Nkusi  1997–2006  2007–2012  Vector elimination (2003–2007)  2016  Eliminated  2013–2016  No  No  Imaramagambo  1991–2012  Not provided  No vector control/elimination activities  2016  Eliminated  2013–2016  No  No  Mount Elgon  1994–2006  2007–2011  Vector elimination (2007–2009)  2016  Eliminated  2012–2015  No  No  Kashoya-Kitomi  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Wambabya-Rwamarongo  1991–2006  2007–2013  Vector elimination (2008–2010)  2017  Eliminated  2014–2017  No  No  Nyamugasani  1993–2015  Not provided  No vector control/elimination activities  2015  Interrupted  2016–2019  No  No  Maracha-Terego  1993–2012  Not provided  No vector control/elimination activities  2014  Interrupted  Not yet  Yes  No  Obongi  1993–2014  Not provided  No vector control/elimination activities  2014  Interrupted  2016–2019  No  No  Wadelai  1993–2005  2006–2010  No vector control/elimination activities  2014  Interrupted  2017–2020  No  No  West Nile  1993–2016  Not provided  No Vector control/elimination activities  2017  Interrupted  2017–2020  No  No  Nyagak-Bondo  1993–2011  2012–present  Vector elimination (2012–2013)  2014  Interruption suspected  Not yet  Yes  Yes  Bwindi  1993–2006  2007–present  No vector Control/elimination activities  2013  Interruption suspected  Not yet  No  Yes  Budongo  1990–2006  2012–present  Vector elimination (2012–2014)  2014  Interruption suspected  Not yet  No  No  Lhubiriha  1993–2014  2015–present  Vector control (2014–present)  Not applicable  Ongoing  Not yet  No  Yes  Madi-Mid North  1994–2011  2012–present  Vector control (2012–present)  Not applicable  Ongoing  Not yet  Yes  Yes  Coordination with the LF program has implications for finances, personnel and time given the need for extended monitoring of entomological indicators stipulated in guidelines. It should be noted that while the current WHO onchocerciasis guidelines require that onchocerciasis PTS can only begin after MDA for LF has stopped, the reciprocal situation is not found in LF operating procedures; for example, post-MDA LF surveillance may launch without regard to ongoing onchocerciasis ivermectin monotherapy MDA since the WHO recommended LF treatment is combined therapy. Cross-border transmission Uganda has possible cross-border transmission with the DRC in the Bwindi, Lhubiriha and Nyagak-Bondo foci as well as with the Republic of South Sudan (RSS) in the Madi-Mid North focus (Table 1). The WHO guidelines will not allow these Uganda foci to be declared as transmission interrupted or eliminated until the extent of these cross-border transmission zones and the status of onchocerciasis elimination efforts on the other side of the border are known. The Ministry of Health in Uganda has recently established effective coordination with its sister Ministry of Health in the DRC that resulted in joint 2016 epidemiological and entomological surveys in border areas. Discussions have also begun with health officials in the RSS to develop similar surveys and other coordinated activities. The Carter Center and Sightsavers have been assisting these activities. Ideally, coordinated joint implementation efforts will soon be carried out in order to interrupt transmission in these shared onchocerciasis foci. However, such shared activities must take into account the security problems in the DRC areas bordering the Bwindi and Lhubiriha foci and in the RSS adjacent to the Madi-Mid North focus. People from the DRC and RSS who cross into Uganda as refugees are highly mobile, moving back and forth between Uganda and their respective countries as the situation dictates. Uganda has made every effort to treat the refugees with ivermectin, but obtaining adequate treatment coverage among these highly mobile populations will be a challenge. Advantages of a national molecular laboratory The presence of a national laboratory avoids the bureaucracy associated with the export of samples and provides timely access to the results by the UOEP and UOEEAC. The personnel in the laboratory are program staff and their workflow is based on priorities set by the UOEEAC. The UOEEAC has recommended that PCR pool screening be used in analysing flies rather than dissections, because of the risk of confusing larvae of Onchocerca (especially O. ochengi).40 The annual cost of laboratory operations is about $35 000 to $40 000. The effect of environmental changes In some foci the vectors have disappeared, presumably the result of environmental changes. The absence of S. neavei is presumed to be due to the disappearance of the freshwater crabs essential for the development of its aquatic stages. This is possibly due to deforestation.42,43 In the Wadelai focus where S. damnosum was presumed to have been the vector, no flies have been captured in recent years, yet no larviciding was ever done and there has been no noticeable change in the Ora and Aroga rivers.43 Also, no vectors have been captured in the (presumed) S. damnosum Obongi focus. It is hypothesized that vector disappearance there was due to poor agricultural practices that increased soil erosion and siltation of vector breeding tributaries flowing into the Nile River. In the Imaramagambo focus, the disappearance of the vector could have been due to runoff into rivers of agricultural chemicals used intensively on the nearby tea plantations.29 Effective communication with communities when stopping MDA and throughout the PTS period A carefully designed communication strategy is needed to explain to communities why MDA is being withdrawn, and these communications should continue throughout the PTS period. In Guatemala, the Knowledge, Attitudes and Practices (KAP) questionnaire surveys in the foci where onchocerciasis was eliminated showed that many persons still want ivermectin and more than a half did not believe that onchocerciasis had been eliminated.44 Our recent KAP experience in Uganda (unpublished) has shown the same attitudes among the people in foci where onchocerciasis has been eliminated. The importance of the UOEEAC in advising WHO guidelines The basis for declaring elimination of onchocerciasis transmission in every Ugandan focus is being meticulously documented and archived so that it can ultimately be made available to the external WHO verification team. To enhance the quality and acceptability of the data, the UOEEAC has worked with Ministry of Health staff to publish the elimination history of each focus in peer-reviewed medical literature. In this way, it is hoped that the quality of the data placed in the national onchocerciasis elimination dossier for Uganda will be incontrovertible.41 Conclusion When Uganda declared an objective of nationwide onchocerciasis elimination by 2020, the tempo of activities accelerated dramatically. Treatment coverage improved under the twice-yearly ivermectin treatment and ground-based larviciding accelerated the interruption of transmission. The new energy motivated targeted communities and was instrumental in keeping health workers focused and interested. The establishment of an independent technical advisory committee, the availability of sensitive and highly specific diagnostic tools at a national laboratory and the obvious annual progress in moving foci along the pathway to elimination are other reasons for the rapid progress towards nationwide onchocerciasis elimination. The main challenge remains cross-border issues with the DRC and RSS, yet the 2020 target for nationwide elimination of onchocerciasis remains within reach. Authors' contributions: As the main author, MNK drafted the manuscript, and all the authors (MNK, TL, PH, TRU, RG, LH, EB, AK, JN, ET and FR) reviewed the manuscript, read and approved the final version. Acknowledgements: We thank and acknowledge all health workers at the district and national levels, the UOEEAC members and the affected communities for their hard work. The late Dr Brian Duke and Dr Frank Walsh (first chair of the UOEEAC), who re-established the Uganda Onchocerciasis Control Program and later persuaded Uganda to take a leadership role in advancing onchocerciasis elimination in Africa, are highly acknowledged. The program could not have succeeded without support from the RBF, CBM, East Ankole Diocese and association of volunteers in international services with Hq in Italy during early 1990s. GTZ and the Bernhard Nocht Institute for Tropical Medicine (Hamburg, Germany) are highly appreciated for supporting a study in 1990 on whether the organophosphate temephos could be safely used to control/eliminate S. neavei, a vector for onchocerciasis in the Kabarole District. The program could not have succeeded in the shift from control to elimination without support from Sightsavers, The Carter Center, John Moores, the LCIF, the Lions Clubs of Uganda, MSD, the Mectizan Donation Program and US Agency for International Development’s ENVISION Project, led by RTI International. We also thank the WHO/African Program for Onchocerciasis Control, WHO Geneva and the Uganda WHO office. Progress towards elimination could not have succeeded if the Uganda Ministry of Health had not provided enabling policies, personnel, office space, laboratory accommodation, and the mechanisms for timely and effective decision-making mechanisms that have kept the program focused and successful. Funding: None. Competing interests: Not required. Ethical approval: Not required. References 1 Barnley GR. Onchocerciasis. Uganda atlas of disease distribution . Nairobi, Kenya: East African Publishing; 1975, p. 38– 40. 2 Raper AB, Lapkin RG. Endemic dwarfism in Uganda. 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International HealthOxford University Press

Published: Mar 1, 2018

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