Metrics details Ivermectin-based preventive chemotherapy (PC) is distributed annually to all at-risk populations eligible for ivermectin treatment to control and/or eliminate onchocerciasis Information on the impact of mass ivermectin administration on onchocerciasis transmission is scanty and it is tricky to appreciate the progress towards elimination and engage corrective measures To fill that gap in the Centre Region in Cameroon the current onchocerciasis endemicity level in the Ndikinimeki Health District after about two decades of mass treatments was assessed A cluster-based cross-sectional survey was carried out in the Ndikinimeki Health District and all volunteers aged ≥ 5 years were (i) interviewed on their compliance to ivermectin over the past five years and (ii) underwent clinical (nodule palpation and visual search for onchocercal lesions) and parasitological examinations (skin snip) for onchocerciasis The overall Onchocerca volvulus prevalence was 7.0% (95% CI: 5.2–9.3%) The prevalence of the disease was significantly higher in the communities Kiboum 1 and Kiboum 2 compared to the other communities (highest prevalence in Makénéné Town Water: 8.5%; 95% CI: 2.3–20.4%) (χ2 = 51.314 The proportion of systematic non-compliers to ivermectin was 23.3% (95% CI: 19.9–27.1%) among individuals interviewed In the sentinel sites (Kiboum communities) onchocerciasis prevalence decreased from 95.2% (95% CI: 88.3–98.1%) to 23.7% (95% CI: 14.7–36.0%) This study has revealed that the Ndikinimeki Health District is hypo-endemic for onchocerciasis after about two decades of preventive chemotherapy with potential hotspots in the Kiboum 1 and Kiboum 2 communities which are known as first-line communities (closest to the breeding sites of the vector) Alternative or complementary strategies to annual ivermectin appear compulsory to accelerate the momentum towards onchocerciasis elimination The pathogenesis of the diseases is essentially due to microfilariae while adult worms usually induce no pathology or simply stimulate the development of characteristic subcutaneous nodules In order to improve current control approaches and define a more pinpointed strategy it is worth carrying out regular surveys to assess the impact of control approaches on the disease epidemiology this study assessed onchocerciasis endemicity in the Ndikinimeki Health District after about two decades of CDTI using a district-wide rather than sentinel site approach A cross-sectional survey was carried out in the Ndikinimeki Health District following a cluster sampling approach Clusters were selected using the probability proportionate to estimate size (PPES) strategy In order to ensure that all clusters have the same probability of selection communities (clusters) were organized into Health Areas prior to the PPES procedure to take into account the difference in the number of communities per Health Area and the difference in community size A total of 12 clusters were selected by the PPES procedure Considering the onchocerciasis prevalence (54.7%) in the Ndikinimeki Health District according to the most recent impact assessment survey (2011) by the National Onchocerciasis Control Programme (NOCP) a minimal sample size of 381 was needed to estimate the true prevalence of onchocerciasis in 2019 in the Ndikinimeki Health District with 5% precision Eligible participants were both males and females and who had been living in the selected clusters for at least 5 years and adherence to ivermectin treatments during the past 5 years preceding the survey were collected from eligible participants using a structured questionnaire individuals aged < 10 years were excluded from history and adherence to CDTI since they are less likely to provide accurate enough answers to such questions All the individuals who accepted to participate underwent clinical and parasitological examinations follow-up of the trend in onchocerciasis prevalence over three decades (or 25 years of annual mass ivermectin treatment) was carried out only in the Boutourou Health Area where a sentinel site (Kiboum communities) was identified during mapping exercise based on the availability of baseline data Both the baseline (1991) and the follow-up (2011) surveys were carried out by the NOCP The number of microfilariae in the fluid was counted (when positive) and the individual microfilarial densities were computed as the arithmetic mean number of microfilariae in the two skin snips (mf/ss) especially after multiple rounds of ivermectin treatments Mann-Whitney and Kruskal–Wallis tests were used to compare onchocerciasis prevalence and mean microfilarial density between clusters The geographical coordinates of each community visited were recorded using a high sensitivity global positioning system [GPS eTrex; Garmin (Europe) Ltd A thematic analysis was performed using a geographical information system (GIS) software (ArcGIS of onchocerciasis point prevalence in the Ndikinimeki Health District; three main layers (roads the latest representing potential blackfly breeding sites) were used to create/illustrate the map A total of 603 participants aged 5 to 88 (median: 32; interquartile range (IQR): 42) years were examined in 12 clusters (communities) of the six Health Areas of the Ndikinimeki Health District The sex ratio (M/F) was 1.04 (proportion of males: 50.9%) Onchocerca volvulus infection rate in the different communities surveyed in the Ndikinimeki Health District The overall prevalence of palpable nodules was 0.3% (95% CI: 0.1–1.2%) ranging between 0–0.6% but the difference was not significant between Health Areas (χ2 = 1.416 The overall prevalence of skin depigmentation and rashes was 3.0% and 0.3% and no significant difference (P > 0.330) was found between Health Areas (χ2 = 5.762 The difference was also not significant between gender groups (χ2 = 0.154 the proportion of individuals affected was significantly higher in the Nyokon Health Area (26.9%; 95% CI: 16.8–40.3%) compared to the other Health Areas (χ2 = 21.925 the difference was also significant when considering clusters (χ2 = 92.731 P < 0.0001) and age groups (χ2 = 18.498 but the difference was not significant when considering gender (χ2 = 1.436 74.8% (95% CI: 71.2–78.1%) of participants reported that they have swallowed ivermectin at least once during the past 5 years The proportion of individuals who reported that they have ingested ivermectin every year during the past 5 years was 34.5% (95% CI: 30.8–38.4%) comparable between males (36.2%; 95% CI: 31.0–41.7%) and females (32.8%; 95% CI: 27.7–38.3%) (χ2 = 0.76 A significant increase in the trend of compliance with ivermectin treatment was observed between the age groups (χ2 = 64.08 P < 0.0001); 22.6% (95% CI: 16.3–30.4%) of participants aged 10–19 years (individuals < 10 years-old excluded) 20.4% (95% CI: 13.5–29.7%) of participants aged 20–34 years 44.0% (95% CI: 35.1–53.4%) of participants aged 35–49 years and 60.3% (95% CI: 53.1–67.1%) of participants aged ≥ 50 years declared having taken ivermectin tablets during the past 5 years The proportion of systematic non-compliers that is those individuals who never ingested ivermectin tablets during the past 5 years slightly higher in females (26.3%; 95% CI: 21.3–31.9%) than in males (20.4%; 95% CI: 15.9–25.7%) although statistically non-significant (χ2 = 2.5 a significantly higher proportion of non-compliance with ivermectin treatment was observed between the age groups (χ2 = 24.59 Participants aged < 34 years exhibited a higher proportion of non-compliance with ivermectin treatment compared to their older counterparts (χ2 = 64.08 31.6% (95% CI: 24.3–39.9%) of participants aged 10–19 years (participants < 10 years-old excluded) 36.6% (95% CI: 27.5–46.7%) of participants aged 20–34 years 15.6% (95% CI: 10.0–23.6%) of participants aged 35–49 years-old and 15.2% (95% CI: 10.7–21.1%) of participants aged ≥ 50 years declared that they have never swallowed ivermectin tablets during the past 5 years A significant decrease in the prevalence of onchocerciasis was observed, between the present findings (2019) and both baseline data (1991) (χ2 = 41.59, df = 1, P < 0.0001), and the first decade trend (2011) (χ2 = 15.25, df = 1, P < 0.0001) (Fig. 2). Trends in Onchocerca volvulus infection rates between 1991 (baseline) and 2019 (follow-up) in the Ndikinimeki Health District Both the baseline (1991) and the follow-up (2011) surveys were carried out by the National Onchocerciasis Control Programme (NOCP) with the support of the African Programme for Onchocerciasis Control (APOC) (NOCP onchocerciasis is known to be naturally cumulative but treatments administered for 18–21 years might have disrupted this relationship thus favoring the shift in prevalence peak among individuals highly exposed and poorly compliant with ivermectin mass treatments In the current situation with the persistence of onchocerciasis in a restricted hotspot area implementation of multiple annual rounds of CDTI complemented with localized vector control by using for example ground larviciding might help boost the momentum towards the elimination of onchocerciasis in the Ndikinimeki Health District and serve as a proof of concept for strategy improvement for countrywide elimination of onchocerciasis This study reveals that the Ndikinimeki Health District is hypo-endemic for onchocerciasis after about two decades of CDTI Despite the low prevalence and intensity of the disease in the study area hotspots for onchocerciasis transmission was found in the Boutourou Health Area (around Kiboum 1 and Kiboum 2 communities) where alternative treatment strategies might be useful to prompt the elimination of onchocerciasis All data generated or analyzed during this study are included in this published article and its additional file community-directed treatment with ivermectin River blindness: a success story under threat WHO. Onchocerciasis: key facts. Geneva: World Health Organization; 2019. https://www.who.int/news-room/fact-sheets/detail/onchocerciasis The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (1) priority areas for ivermectin treatment WHO. Blindness and vision impairment-fact sheets. Geneva: World Health Organization; 2019. https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment CDC. Parasites- onchocerciasis (also known as river blindness). Review. Atlanta: Centers for Disease Control and Prevention; 2013. https://www.cdc.gov/parasites/onchocerciasis/index.html The macrofilaricidal efficacy of repeated doses of ivermectin for the treatment of river blindness The reproductive lifespan of Onchocerca volvulus in west African savanna WHO. Progress report on the elimination of human onchocerciasis 2015–2016. Geneva: World Health Organization; 2016. https://apps.who.int/iris/bitstream/handle/10665/275983/WER9347.pdf?ua=1 Feasibility of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: first evidence from studies in Mali and Senegal Impact of long-term treatment of onchocerciasis with ivermectin in Kaduna State Nigeria: first evidence of the potential for elimination in the operational area of the African Programme for Onchocerciasis Control Proof-of-principle of onchocerciasis elimination with ivermectin treatment in endemic foci in Africa: final results of a study in Mali and Senegal Prevalence of onchocerciasis in the Fundong Health District Cameroon after 6 years of continuous community-directed treatment with ivermectin Still mesoendemic onchocerciasis in two Cameroonian community-directed treatment with ivermectin projects despite more than 15 years of mass treatment Ongoing transmission of Onchocerca volvulus after 25 years of annual ivermectin mass treatments in the Vina du Nord River Valley On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: better understanding transmission dynamics to inform changes in programmatic interventions Health populations denominators 2017—Cameroon Diagnosis and extirpation of nodules in human onchocerciasis A rapid mapping technique for the prevalence and distribution of onchocerciasis: a Cameroon case study An attempt to normalize the methodology of clinico-parasitologic surveys of onchocerciasis in West Africa (author’s transl) A force-of-infection model for onchocerciasis and its applications in the epidemiological evaluation of the Onchocerciasis Control Programme in the Volta River basin area Important progress towards elimination of onchocerciasis in the West Region of Cameroon Study on the prevalence of Onchocerca volvulus infection among the inhabitants of Awgu and Oji River Local Government Areas of Enugu State Required duration of mass ivermectin treatment for onchocerciasis elimination in Africa: a comparative modelling analysis Alternative treatment strategies to accelerate the elimination of onchocerciasis Download references The authors are thankful to the local authorities for their assistance during the implementation of this study and to the population who willingly accept to participate in this study This work was supported by authors’ personal funds; fees related for field work were covered by RAA Centre for Research on Filariasis and other Tropical Diseases (CRFilMT) RAA conceived the study and designed the experiments analyzed the data and drafted the manuscript LS conceived the study and designed the experiments supervised and coordinated the study and helped to draft the manuscript NHN conceived the study and designed the experiments and helped to draft the manuscript JB collected field data and contributed to the preparation of the manuscript RHB collected field data and contributed to the preparation of the manuscript HCND conceived the study and designed the experiments All authors read and approved the final manuscript Ethical clearance was granted by the Centre Regional Ethics Committee for Human Health Research (N°667/CRERSH/2019) and Administrative authorization was granted by the Regional Delegation of Public Health and the Ndikinimeki Health District After approval of the local administrative and traditional authorities the objectives and schedules of the study were first explained to community leaders and to all eligible individuals informed consents were obtained from participants or their parents or guardians (for minors) who agreed to participate An individual barcode was attributed to each participant for anonymous data analysis The authors declare that they have no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Prevalence and intensity of onchocerciasis in the different clusters of the Ndikinimeki Health District unless otherwise stated in a credit line to the data Download citation DOI: https://doi.org/10.1186/s13071-020-04387-6 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Rural women of the Mbam-et-Inoubou division of the Centre Region have been served farming equipment to boost production and better their standards of living The material handed over to the women of nine sub-divisions of Mbam-et-Inoubou (Deuk Makénéné and Bokito ) by a network of agricultural farming association of the division (Rafami) at the weekend comprised hoes motorcycles and others to the tune of about 3 million CFA francs is quoted to have challenged the recipients to judiciously use the material so as to journey out of subsistence agriculture reportedly told the women to use the material to kick poverty from among them 14-09-2013 - Industrial Cassava Processing Underway in Sangmelima Kribi Bitumen Plant Set to Start Construction in 2025 with Government Backing CEMAC Bond Market Hits CFA 8.45 Trillion in March 2025, Interest Rates Drop Cameroon’s Timber Output Projected to Rise in 2025 Despite Higher Export Taxes Central Africa Stock Exchange Sees 98% Drop in Trading Value in Q1 2025 Every week the economy and investment news from Cameroon Mboa Paris Trains 30 Young Cameroonians to Boost Tech and Entrepreneurship Cameroon Audit Targets Former Officials for Mismanagement in Agricultural Project Camwater Seeks Global Bids to Launch Bottled Water Lines in Five Cities Bafoussam Workshop Highlights Benefits of Cameroon-EU Trade Agreement Cameroon Could Reach 350,100 Tons of Cotton in 2025 (Beac) Paul Biya Appoints Johnny Razack as Chair of Cameroon’s National Investment Company Cameroon Refuses Work Visa Renewal for Casino and Super U Boss Over Toxic Workplace Claims Cameroon Joins Global Charter to Fight Illegal Fishing