Rapid Epidemiological Mapping Of Onchocerciasis Research Articles

Onchocerciasis control in Ghana (1974\u20132016)

BackgroundThe control of onchocerciasis in Ghana started in 1974 under the auspices of the Onchocerciasis Control Programme (OCP). Between 1974 and 2002, a combination of approaches including vector control, mobile community ivermectin treatment, and community-directed treatment with ivermectin (CDTI) were employed. From 1997, CDTI became the main control strategy employed by the Ghana OCP (GOCP). This review was undertaken to assess the impact of the control interventions on onchocerciasis in Ghana between 1974 and 2016, since which time the focus has changed from control to elimination.MethodsIn this paper, we review programme data from 1974 to 2016 to assess the impact of control activities on prevalence indicators of onchocerciasis. This review includes an evaluation of CDTI implementation, microfilaria (Mf) prevalence assessments and rapid epidemiological mapping of onchocerciasis results.ResultsThis review indicates that the control of onchocerciasis in Ghana has been very successful, with a significant decrease in the prevalence of infection from 69.13% [95% confidence interval) CI 60.24–78.01] in 1975 to 0.72% (95% CI 0.19–1.26) in 2015. Similarly, the mean community Mf load decreased from 14.48 MF/skin snip in 1975 to 0.07 MF/skin snip (95% CI 0.00–0.19) in 2015. Between 1997 and 2016, the therapeutic coverage increased from 58.50 to 83.80%, with nearly 100 million ivermectin tablets distributed.ConclusionsDespite the significant reduction in the prevalence of onchocerciasis in Ghana, there are still communities with MF prevalence above 1%. As the focus of the GOCP has changed from the control of onchocerciasis to its elimination, both guidance and financial support are required to ensure that the latter goal is met.Graphical

Assessing Hypoendemic Onchocerciasis in Loa loa Endemic Areas of Southeast Nigeria.

.Nigeria changed its goal for onchocerciasis from control to transmission elimination. Under the control program, ivermectin mass drug administration (MDA) focused only on hyper/meso-endemic local government areas (LGAs) identified by Rapid Epidemiological Mapping of Onchocerciasis as having ≥ 20% nodule rates. Because transmission is likely in some LGAs where nodule rates are < 20%, the new elimination paradigm requires MDA expansion. Determining which hypoendemic areas require MDA, termed onchocerciasis elimination mapping, is a major challenge. In 2016, we studied 19 ivermectin-naive hypoendemic LGAs in southern Nigeria that bordered LGAs under MDA. Fifty adults and 50 children (aged 5–10 years) were tested in 110 villages for onchocerciasis IgG4 antibody using an Ov16 rapid diagnostic test (RDT). A 10% subset of subjects provided a blood spot for confirmatory Ov16 ELISA. The mean prevalence of RDT positives was 0.5% in the 5,276 children tested (village range, 0.0–4.0%) versus 3.3% in 5,302 adults (village range, 0.0–58.0%). There was 99.3% agreement between the Ov16 RDT and ELISA. Six different MDA launch thresholds were applied to the RDT results based on different recommendations by the Nigeria Onchocerciasis Elimination Committee and the Onchocerciasis Technical Advisory Subgroup of the WHO. Mass drug administration targets for the same area varied tenfold by threshold chosen, from one LGA (population to be treated 221,935) to 13 LGAs (population 2,426,987). Because the Ov16 threshold selected will have considerable cost and resource implications, the decision to initiate MDA should incorporate entomological data demonstrating onchocerciasis transmission.

Mapping the burden of onchocercal skin disease.

Onchocerciasis is a neglected tropical disease caused by a nematode parasite, Onchocerca volvulus, and transmitted by bites of Simulium blackflies which breed near fast-flowing rivers. In humans, thousands of microfilariae (immature worms) migrate to the skin and eyes where they cause pathology. Historically, much research was devoted to the serious effect of blindness, from which the disease earns its alternative name of 'river blindness'. Mapping the burden of onchocercal skin disease (OSD) was expedited by the development of a clinical classification and grading system that facilitated comparison of data from different countries. After successful field testing in Nigeria, the classification scheme was used in a multicountry study in seven endemic sites, to estimate the true burden of OSD across Africa. High levels of OSD were found, affecting 28% of the population. A new control programme, the African Programme for Onchocerciasis Control (APOC) was launched in 20 countries using annual doses of ivermectin, donated by Merck & Co., Inc. The multicountry study also found a close correlation between the levels of itching and OSD with the level of endemicity, as determined by the prevalence of onchocercal nodules. This enabled APOC to use Rapid Epidemiological Mapping of Onchocerciasis, which entailed identifying likely vector breeding sites near rivers, then sampling 50 adult males in nearby villages to determine the prevalence of nodules and delineate which villages required treatment. Onchocerciasis is now targeted for elimination in Africa, and the challenge is to complete Onchocerciasis Elimination Mapping of hypoendemic areas using serology.

High prevalence of epilepsy in an onchocerciasis endemic health zone in the Democratic Republic of the Congo, despite 14 years of community-directed treatment with ivermectin: A mixed-method assessment

ObjectivesTo investigate the reasons for the high prevalence of epilepsy (>6%) discovered in 2015 in the Aketi health zone in the north of the Democratic Republic of the Congo. MethodsPersons with epilepsy (PWE) diagnosed in a door-to-door survey in 2015 were traced and re-examined in 2017 by a neurologist. Confirmed PWE were paired with matched controls. For onchocerciasis assessment, children 7–10 years old were tested for IgG4 Onchocerca volvulus (OV16) antibodies, a rapid epidemiological mapping of onchocerciasis (REMO) study was performed, and ivermectin coverage was investigated. ResultsForty-three (61.4%) previously diagnosed PWE were traced; the neurologist confirmed the epilepsy diagnosis in all of them. The overall OV16 positivity rate was 64.5%. Poor ivermectin coverage (55.9%) and a high prevalence of onchocercal nodules (>70%) were observed. The prevalence of epilepsy was 5.7% in Aketi rural town, with nine PWE (13.8%) experiencing head nodding seizures. A case-control study showed that PWE had lower body weight and higher ivermectin coverage in 2017 than healthy controls. ConclusionsThe high prevalence of epilepsy in the Aketi health zone, despite 14 years of community-directed treatment with ivermectin (CDTI), was found to be associated with high onchocerciasis transmission and low ivermectin use. An awareness programme to increase ivermectin coverage and the introduction of a bi-annual CDTI programme should be considered.

Seroprevalence of onchocerciasis in Ogun State, Nigeria after ten years of mass drug administration with ivermectin

Background: This serological study conducted between March and July 2015 investigated the status of onchocerciasis in Ogun State, Nigeria after a decade of mass drug administration (MDA) with ivermectin. Baseline information from the rapid epidemiological mapping of onchocerciasis (REMO) prior to MDA had indicated that Ogun State was meso-endemic to onchocerciasis. Following years of treatment with ivermectin, it has become important to investigate the current status of the disease using more sensitive diagnostic methods.Methods: The study was conducted in 32 communities in eight onchocerciasis-endemic local government areas (LGAs). Using the Ov16 rapid diagnostic test (Ov16 RDT), finger-prick whole blood was obtained from 3 895 consented participants from age five and above. Skin snips were obtained from a subset of 481 corresponding participants as the majority of community members did not consent to skin snipping.Results: Study revealed a cumulative seroprevalence of 9.3% (CI 9.29–9.31%) by RDT and 17.3% (CI 16.73–18.34%) microfilaridermia prevalence by the skin snip subset. Seroprevalence among children between the ages of five and nine was 2.9% (CI 1.74–3.53%) across all LGAs. A community microfilaria load (CMFL) between 0 and 1.21 MF/skin snip was recorded in the different communities studied. Among the studied LGAs, children in Odeda LGA recorded the highest seroprevalence by RDT (14.9%) followed by Abeokuta North (5.1%), Abeokuta South (4.8%) and Imeko-Afon (0.6%), while Ewekoro, Ifo, Obafemi-Owode and Yewa North LGAs recorded zero prevalence.Conclusion: It appears that the elimination of onchocerciasis in some LGAs is possible considering the lack of new infection among children and the hypo-endemicity among the adult population. However, the microfilaria prevalence observed among adults is of concern as it may imply that mass treatment has not been effective. Increased therapeutic coverage is advised to fully maximise the potential of ivermectin treatment to achieve the disease elimination.

Rapid integrated clinical survey to determine prevalence and co-distribution patterns of lymphatic filariasis and onchocerciasis in a Loa loa co-endemic area: The Angolan experience

The Republic of Angola is a priority country for onchocerciasis and lymphatic filariasis (LF) elimination, however, the co-distribution of the filarial parasite Loa loa (loiasis) is a significant impediment, due to the risk of severe adverse events (SAEs) associated with ivermectin used in mass drug administration (MDA) campaigns. Angola has a high risk loiasis zone identified in Bengo Province where alternative interventions may need to be implemented; however, the presence and geographical overlap of the three filarial infections/diseases are not well defined. Therefore, this study conducted a rapid integrated filarial mapping survey based on readily identifiable clinical conditions of each disease in this risk zone to help determine prevalence and co-distribution patterns in a timely manner with limited resources. In total, 2007 individuals from 29 communities in five provincial municipalities were surveyed. Community prevalence estimates were determined by the rapid assessment procedure for loiasis (RAPLOA) and rapid epidemiological mapping of onchocerciasis (REMO) together with two questions on LF clinical manifestations (presence of lymphoedema, hydrocoele). Overall low levels of endemicity, with different overlapping distributions were found. Loiasis was found in 18 communities with a prevalence of 2.0% (31/1571), which contrasted to previous results defining the area as a high risk zone. Onchocerciasis prevalence was 5.3% (49/922) in eight communities, and LF prevalence was 0.4% for lymphoedema (8/2007) and 2.6% for hydrocoeles (20/761 males) in seven and 12 communities respectively. The clinical mapping survey method helped to highlight that all three filarial infections are present in this zone of Bengo Province. However, the significant difference in loiasis prevalence found between the past and this current survey suggests that further studies including serological and parasitological confirmation are required. This will help determine levels of infection and risk, understand the associations between clinical, serological and parasitological prevalence patterns, and better determine the most appropriate treatment strategies to reach onchocerciasis and LF elimination targets in the loiasis co-endemic areas. Our results also suggest that the utility of the earlier RAPLOA derived maps, based on surveys undertaken over a decade ago, are likely to be invalid given the extent of population movement and environmental change, particularly deforestation, and that fine scale micro-mapping is required to more precisely delineate the interventions required defined by these complex co-endemicities.

Onchocerciasis, an undiagnosed disease in Mozambique: identifying research opportunities.

BackgroundThe objective of this paper is to summarise and critically review the available data about onchocerciasis in Mozambique, in order to report epidemiological and clinical aspects related to the disease and identify gaps in knowledge. The paper is intended to raise awareness of the existence and importance of this disease and to define research priorities.MethodsWe examined the scarce epidemiological data at our disposal: two diagnostic studies in 1997 and 1998 (first reports on the existence of onchocerciasis in Mozambique), and two Rapid Epidemiological Mapping of Onchocerciasis (REMO) surveys in 2001 and 2007. We examined differences in study designs and methodologies as well as the differing geographical locations to explain the divergence in findings among the studies.ResultsEvidence indicates that onchocerciasis is hypoendemic in Mozambique (with national and imported cases), but still largely remains an undiagnosed illness. There is no awareness of the clinical aspects of the disease and nor of the differential diagnosis with lepromatous leprosy and dermatitis caused by Scabies spp. The use of skin biopsy and a symptom screening questionnaire, combined with nodule rate, in the first two studies may have captured even atypical or subacute presentations. Both REMO surveys relied solely on nodule detection and in the six years between the two studies, the prevalence of nodules detected more than doubled.ConclusionsThe epidemiology and clinical aspects of the disease are unknown in Mozambique. Since the last REMO took place in 2007 and since the population is subject to large-scale movement and displacement, it is important to develop tools to identify and analyse populations that are at high risk for onchocerciasis. Cases of onchocerciasis may be misdiagnosed as leprosy or scabies that fail to improve despite being subjected to treatment against leprosy. Techniques to enable a differential diagnosis need to be established by training health professionals on the recognition of this undiagnosed disease. It is equally necessary to identify the blackfly vectors and where they breed.

The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (1) priority areas for ivermectin treatment.

BackgroundThe African Programme for Onchocerciasis Control (APOC) was created to control onchocerciasis as a public health problem in 20 African countries. Its main strategy is community directed treatment with ivermectin. In order to identify all high risk areas where ivermectin treatment was needed, APOC used Rapid Epidemiological Mapping of Onchocerciasis (REMO). REMO has now been virtually completed and we report the results in two articles. The present article reports the mapping of high risk areas where onchocerciasis was a public health problem. The companion article reports the results of a geostatistical analysis of the REMO data to map endemicity levels and estimate the number infected.MethodsREMO consists of three stages: exclusion of areas that are unsuitable for the vector, selection of sample villages to be surveyed in each river basin, and examination of 30 to 50 adults for the presence of palpable onchocercal nodules in each selected village. The survey results and other relevant information were processed in a geographical information system. A panel of experts interpreted the data taking the river-based sampling into account and delineated high risk areas where the prevalence of nodules is greater than 20%.ResultsUnsuitable areas were identified in eight countries. In the remaining areas surveys were done in a total of 14,473 sample villages in which more than half a million people were examined. High-risk areas were identified in 18 APOC countries, ranging from small isolated foci to a vast contiguous endemic area of 2 million km2 running across seven countries. In five countries the high risk area covered more than 48% of the total surface area, and 31% to 48% of the population. It is estimated that 86 million people live in high risk areas in the APOC countries.ConclusionsThe REMO maps have played a significant role in onchocerciasis control in the 20 APOC countries. All high-risk areas where onchocerciasis used to be a serious public health problem have been clearly delineated. This led to the creation of community-directed treatment projects that by 2012 were providing annual ivermectin treatment to over 80 million people.

The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (2) pre-control endemicity levels and estimated number infected.

BackgroundThe original aim of the African Programme for Onchocerciasis Control (APOC) was to control onchocerciasis as a public health problem in 20 African countries. In order to identify all high risk areas where ivermectin treatment was needed to achieve control, APOC used Rapid Epidemiological Mapping of Onchocerciasis (REMO). REMO involved spatial sampling of villages to be surveyed, and examination of 30 to 50 adults per village for palpable onchocercal nodules. REMO has now been virtually completed and we report the results in two articles. A companion article reports the delineation of high risk areas based on expert analysis. The present article reports the results of a geostatistical analysis of the REMO data to map endemicity levels and estimate the number infected.MethodsA model-based geostatistical analysis of the REMO data was undertaken to generate high-resolution maps of the predicted prevalence of nodules and of the probability that the true nodule prevalence exceeds the high risk threshold of 20%. The number infected was estimated by converting nodule prevalence to microfilaria prevalence, and multiplying the predicted prevalence for each location with local data on population density. The geostatistical analysis included the nodule palpation data for 14,473 surveyed villages.ResultsThe generated map of onchocerciasis endemicity levels, as reflected in the prevalence of nodules, is a significant advance with many new endemic areas identified. The prevalence of nodules was > 20% over an area of 2.5 million km2 with an estimated population of 62 million people. The results were consistent with the delineation of high risk areas of the expert analysis except for borderline areas where the prevalence fluctuated around 20%. It is estimated that 36 million people would have been infected in the APOC countries by 2011 if there had been no ivermectin treatment.ConclusionsThe map of onchocerciasis endemicity levels has proven very valuable for onchocerciasis control in the APOC countries. Following the recent shift to onchocerciasis elimination, the map continues to play an important role in planning treatment, evaluating impact and predicting treatment end dates in relation to local endemicity levels.

Integrated rapid mapping of onchocerciasis and loiasis in the Democratic Republic of Congo: Impact on control strategies

BackgroundOnchocerciasis can be effectively controlled by annual mass treatment with ivermectin in endemic communities. However, in communities that are endemic for loiasis there may be significant risk of severe adverse reactions after ivermectin treatment. Planning of control requires therefore mapping of these two infections using rapid assessment tools developed for each disease. These tools were initially implemented independently till the feasibility of combining them was demonstrated. This paper reports the results of integrated mapping in four epidemiological zones in the Democratic Republic of Congo and its implications on operational decision-making on ivermectin treatment. MethodsRapid assessment surveys were conducted between 2004 and 2005 using both rapid epidemiological mapping of onchocerciasis (REMO) and rapid assessment procedure for loiasis (RAPLOA). The survey results were subjected to a spatial analysis in order to generate for each of the two diseases maps of the estimated prevalence of infection throughout the four zones. ResultsSurveys were undertaken in 788 villages where 25,754 males were examined for palpable onchocercal nodules and 62,407 people were interviewed for history of eye worm. The results showed major differences in the geographic distribution of the two diseases. Loiasis was highly endemic in some areas, where special precautions were required, but not in others where routine ivermectin treatment could proceed. ConclusionIntegrated rapid mapping of onchocerciasis and loiasis reduces both time and cost of surveys and greatly facilitates operational decision-making on ivermectin treatment in areas where loiasis might be co-endemic.

Filaria control and elimination: diagnostic, monitoring and surveillance needs

Gold standard diagnosis using blood films or skin snips has dimished relevance as mass drug distribution programmes for control of filaria infections expand. The view of 'diagnosis' and its relevance at the individual level has changed, as it has been recognised that the spectrum of programmatic processes (mapping, mass drug interventions, monitoring and evaluation, and surveillance) require different approaches as different questions are asked at each stage. The feasibility and relevance of skin biopsy or blood film examination is challenged when mass drug distribution seeks to treat all eligibles in communities. The need to expand programmes rapidly by identifying the highest risk communities has seen the development of rapid assessment methods, such as rapid epidemiological mapping of onchocerciasis (REMO) and rapid epidemiological assessment (REA) for onchocerciasis, immunochromatographic test (ICT)-based mapping for lymphatic filariasis (LF), and Rapid Assessment Procedure for Loiasis (RAPLOA) for Loa, to reduce the risk of serious adverse events and to guide projects in high-risk communities. As programmes reduce the prevalence through mass drug distribution, more sensitive techniques are required to define endpoints, for LF in particular where the programmatic goal is elimination; for onchocerciasis, sensitive surveillance tools are required particularly in those areas where such risks of recrudescence are high. Whilst much progress has been made in the development and deployment of rapid methods, there are still specific needs for antigen detection in onchocerciasis, whilst standardisation of a panel of tools for LF will allow the definition of endpoint parameters so that countries can decide when mass drug administration (MDA) can be stopped and have a sensitive post-MDA surveillance system.

Rapid epidemiological mapping of onchocerciasis (REMO) in Ini and Ibiono Ibom local government areas of Akwa Ibom State, Nigeria

Rapid epidemiological mapping of onchocerciasis (REMO) in Ini and Ibiono Ibom local government areas of Akwa Ibom State, Nigeria

Development and evaluation of an antigen detection dipstick assay for the diagnosis of human onchocerciasis

To improve on the diagnosis of onchocerciasis, especially light infections, we developed and evaluated an oncho-dipstick test based on the detection of Onchocerca volvulus specific antigens in urine and tears. The test was able to detect as little as 25 ng/ml of parasite specific antigens in samples and took as little as 3 h. Evaluation of the assay on 456 residents of an onchocerciasis hyperendermic area in Cameroon resulted in 408 (89.5%) positives in urine and 374 (82%) positives in tears. The prevalence of onchocerciasis in the study area, as determined by Rapid Epidemiological Mapping of Onchocerciasis (REMO) and skin snip methods, was 52 and 36.8%, respectively. The sensitivity of the oncho-dipstick assay was 100% in urine and 92% in tears; its specificity was 100% in both. Concordance between urine and tear test results from the same individuals was 87%. The test strips were sufficiently reactive when left at room temperature for up to 8 months. The test would be useful for laboratory diagnosis of onchocerciasis in low transmission zones and to ascertain successful treatment of patients in experimental drug studies.

Final report of the Conference on the eradicability of Onchocerciasis

Sixty-four experts from a variety of disciplines attended a Conference on the Eradicability of Onchocerciasis at The Carter Center, in Atlanta GA, held January 22-24, 2002. The Conference, which was organized by The Carter Center and the World Health Organization, with funding from the Bill & Melinda Gates Foundation, addressed the question: "Is onchocerciasis (River Blindness) eradicable with current knowledge and tools?" Former US President Jimmy Carter attended part of the final plenary proceedings on January 24.The Conference consisted of a series of presentations by invited expert speakers (Appendix C) and further deliberations in four workgroups (Appendix D) followed by plenary discussion of major conclusions. The presentations underlined epidemiological and entomological differences between onchocerciasis in Africa and the Americas. Whilst onchocerciasis in Africa covers extensive areas and is associated with striking human and fly population migrations and remarkably efficient black fly vectors, in the Americas onchocerciasis is found in limited foci. Human and fly population migration are not major problems in the Americas, where most black fly species are inefficient, though some efficient black flies are also found there. Vector control has been effectively applied in the Onchocerciasis Control Program in West Africa (OCP) with remarkable results, interrupting transmission in most parts of the original Program area. The use of ivermectin has given variable results: while ivermectin treatment has been effective in all endemic areas in controlling onchocerciasis as a public health problem, its potential for interrupting transmission is more promising in hypo- and mesoendemic areas. The African Program for Onchocerciasis Control (APOC), which supports onchocerciasis control in endemic African countries outside the OCP, applies ivermectin, its principal control tool, to communities in high-risk areas as determined by rapid epidemiological mapping of onchocerciasis (REMO) and Geographic Information Systems (GIS). In the Americas, through support of the Onchocerciasis Elimination Program in the Americas (OEPA), a strategy of bi-annual ivermectin treatment of at least 85% of the eligible populations in all endemic communities is showing very good results and promises to be effective in eliminating onchocerciasis in the region.The Conference concluded that onchocerciasis is not eradicable using current tools due to the major barriers to eradication in Africa. However, the Conference also concluded that in most if not all the Americas, and possibly Yemen and some sites in Africa, transmission of onchocerciasis can be eliminated using current tools. The Conference recommended that where interruption of transmission is feasible and cost effective, programs should aim for that goal using all appropriate and available interventions so that the Onchocerca volvulus can eventually be eliminated and interventions halted. Although interruption of transmission of onchocerciasis cannot currently be achieved in most of Africa, the Conference recommended that efforts be made to preserve areas in West Africa made free of onchocerciasis transmission through the Onchocerciasis Control Program over the past 25 years. In the remaining hyper and mesoendemic foci in Africa, continued annual distribution of ivermectin will keep onchocerciasis controlled to a point where it is no longer a public health problem or constraint to economic development.

Rapid epidemiological mapping of onchocerciasis (REMO): its application by the African Programme for Onchocerciasis Control (APOC).

One of the fundamental challenges that the African Programme for Onchocerciasis Control (APOC) has had to face is how to identify the endemic communities where its mass ivermectin-treatment operations are to be carried out in conformity with its stated objective of targetting the most highly endemic, affected and at-risk populations. This it has done by adopting a technique, known as the rapid epidemiological mapping of onchocerciasis (REMO), that provides data on the distribution and prevalence of onchocerciasis. Integration of the REMO data into a geographical information system (GIS) enables delineation of zones of various levels of endemicity, and this is an important step in the planning process for onchocerciasis control. Zones are included in (or excluded from) the APOC-funded programme of community-directed treatment with ivermectin (CDTI), depending on whether or not their levels of onchocercal endemicity reach the threshold set by APOC. This review describes the application of the REMO/GIS technique by APOC in its operations, and identifies the remaining related challenges.

The achievements and challenges of the African Programme for Onchocerciasis Control (APOC).

The main strategy of APOC, of community-directed treatment with ivermectin (CDTI), has enabled the programme to reach, empower and bring relief to remote and under-served, onchocerciasis-endemic communities. With CDTI, geographical and therapeutic coverages have increased substantially, in most areas, to the levels required to eliminate onchocerciasis as a public-health problem. Over 20 million people received treatment in 2000. APOC has also made effective use of the combination of the rapid epidemiological mapping of onchocerciasis (REMO) and geographical information systems (GIS), to provide information on the geographical distribution and prevalence of the disease. This has led to improvements in the identification of CDTI-priority areas, and in the estimates of the numbers of people to be treated. A unique public-private-sector partnership has been at the heart of APOC's relative success. Through efficient capacity-building, the programme's operations have positively influenced and strengthened the health services of participating countries. These laudable achievements notwithstanding, APOC faces many challenges during the second phase of its operations, when the full impact of the programme is expected to be felt. Notable among these challenges are the sustainability of CDTI, the strategy's effective integration into the healthcare system, and the full exploitation of its potential as an entry point for other health programmes. The channels created for CDTI, could, for example, help efforts to eliminate lymphatic filariasis (which will feature on the agenda of many participating countries during APOC's Phase 2). However, these other programmes need to be executed without compromising the onchocerciasis-control programme itself. Success in meeting these challenges will depend on the continued, wholehearted commitment of all the partners involved, particularly that of the governments of the participating countries.

Cross-validation of the rapid epidemiological mapping of onchocerciasis endemicity in Anambra state, Nigeria.

In this evaluation study, the results of a previous, rapid, epidemiological mapping of onchocerciasis (REMO) from quota samples of six communities (two hyper-, two meso-, one hypo- and one non-endemic) in Anambra state, Nigeria, were cross-validated. The findings were based on observations on the prevalence of palpable onchocercal nodules and skin dipigmentation (leopard skin) in a sample of 50 adults resident in each community for at least 5 years. They indicate that the REMO results obtained earlier were reasonably valid. The influence of several factors (mobilization techniques, mobilization message, previous exposure of subjects to previous research studies and treatment intervention, community members' perception of susceptibility and their desire to benefit from treatment programmes) on the representativeness of cases and non-cases in the samples used for REMO is discussed.

Human onchocerciasis: current assessment of the disease burden in Nigeria by rapid epidemiological mapping

Rapid epidemiological mapping of onchocerciasis (REMO) was carried out in Nigeria between 1994 and 1996, to provide accurate estimates of the populations living in high-risk areas for the disease and to identify the communities to be given priority treatment with Mectizan (ivermectin, MSD). The rapid epidemiological assessment (REA) teams which carried out the survey comprised epidemiologists, geographers, and entomologists. They used topographical maps, at a scale of 1:250,000, to select sample villages at 30-km intervals along selected river courses. Several non-governmental development organizations participated in the surveys, providing support to the teams. In each study community, 50 adult males who had lived in the area for at least 10 years were randomly selected and examined for the presence of palpable, onchocercal nodules. The REA results were cross-validated by an independent REMO expert and then presented, initially as percentage prevalences in pie-chart form, using a geographical information system. The number of Nigerians living in high-risk areas (demarcated by river systems with villages that had > or = 19% prevalence) and who therefore require urgent Mectizan treatment, was estimated as 13,809,313. The national REMO map produced is allowing the African Programme for Onchocerciasis Control's technical consultative committee to prioritize the approval of proposals submitted from Nigeria in a rational and effective manner.

Human onchocerciasis: current assessment of the disease burden in Nigeria by rapid epidemiological mapping

Rapid epidemiological mapping of onchocerciasis (REMO) was carried out in Nigeria between 1994 and 1996, to provide accurate estimates of the populations living in high-risk areas for the disease and to identify the communities to be given priority treatment with Mectizan (ivermectin, MSD). The rapid epidemiological assessment (REA) teams which carried out the survey comprised epidemiologists, geographers, and entomologists. They used topographical maps, at a scale of 1:250 000, to select sample villages at 30-km intervals along selected river courses. Several non-governmental development organizations participated in the surveys, providing support to the teams.In each study community, 50 adult males who had lived in the area for at least 10 years were randomly selected and examined for the presence of palpable, onchocercal nodules. The REA results were cross-validated by an independent REMO expert and then presented, initially as percentage prevalences in pie-chart form, using a geographical information system. The number of Nigerians living in high-risk areas (demarcated by river systems with villages that had ≥ 19% prevalence) and who therefore require urgent Mectizan treatment, was estimated as 13 809 313. The national REMO map produced is allowing the African Programme for Onchocerciasis Control's technical consultative committee to prioritize the approval of proposals submitted from Nigeria in a rational and effective manner.

Country-wide rapid epidemiological mapping of onchocerciasis (REMO) in Cameroon

The prevalence of infection in local communities has been used as the basis for the country-wide repartition of onchocerciasis in Cameroon, following the principles for rapid epidemiological mapping of onchocerciasis (REMO) developed by the World Health Organization. The levels of endemicity were evaluated in 349 villages by rapid epidemiological assessment (REA), a method based on the examination of nodules in males aged > or = 20 years. An onchocerciasis map was then drawn from the epidemiological data which had been collected previously, from clinico-parasitological surveys based on the examination of skin snips, and the results of the REA surveys. The REMO surveys allowed the main onchocerciasis foci in Cameroon to be accurately delineated, and several small endemic areas which had never been reported before to be identified. The total 'at risk' population (i.e. those for which ivermectin treatment should be considered as urgent or highly desirable) was estimated by combining the epidemiological results and the demographical data available from an administrative census. Those at risk were estimated to number 3.5 million, representing about 50% of the total rural population in Cameroon.