Introduction: There is an increasing need in combining to ivermectin mass distribution, complementary strategies to accelerate onchocerciasis elimination in endemic areas. In this context, the physical destruction of Simulium breeding sites was piloted in Pouth-Kelle community.

Material and Methods: The S&C was implemented in Pouth-Kelle by community volunteers at a regular frequency in the river section of ≈ 3 kilometers. The study was carried out over 2 years between January 2021 and December 2022. Adult female blackflies were collected 3 days per month by human landing catch technique and the S&C vector control was implemented once a month at regular frequency in 2022. Its ownership and sustainability in the surveyed community were investigated among community members.

Results: A total of 10,599 female blackflies were collected over the study period, including 9,163 specimens in 2021 and 1,436 in 2022. During the S&C vector control implementation in 2022, the reduction in the number of bites varied between 70% and 100%. Regarding the importance of the tested vector control strategy, 97% of the interviewees said it was highly beneficial for the community with a drastic reduction of blackfly nuisance observed in 2022. Its ownership by the community was conditioned by financial and material incentives.

Conclusion: The S&C vector control trial led to a significant reduction in blackfly aggressiveness in the Pouth-Kelle community. Although this approach provides well-being for community residents, its ownership and sustainability remain an issue to be considered for a decision-making in endemic communities, local healthcare systems and professionals.

Onchocerciasis, Slash and Clear, Elimination, Ownership, Pouth-Kelle, Cameroon

Human onchocerciasis and its vectors Simulium blackflies are widely distributed in the world with the highest proportion of the disease and greatest vector diversity found in Sub-Saharan Africa (SSA) [1-4]. This affection has a long morbidity and mortality history in SSA where two main control strategies have so far been implemented on a large scale to spare human populations from its clinical effects. The first control strategy was vector control, implemented in West Africa region between 1974-2002 by ?Onchocerciasis Control Programme? (OCP). The aim of OCP was to reduce the burden of the disease through ground larviciding so that it should no longer be considered as a public health problem or an obstacle for the socio-economic development of populations in the sub-region [5]. After ≈ 30 years of active deployment of this strategy, a significant reduction in vector population densities and clinical signs of onchocerciasis in human populations were noted in some countries in West Africa [6,7]. However, the cost of the deployed vector control operations as well as the necessary logistics have led in stopping the activities of this programme.

The second control strategy was adopted to break the disease transmission cycle by eliminating infesting stages of Onchocerca volvulus (Nematoda: Filaroidea) in infected humans through ivermectin-based treatment. Ivermectin is a safe and effective microfilaricide known under the trade name Mectizan®. It was registered for human use in 1987 and the same year, the pharmaceutical company Merck & Co announced its free donation with the goal of making it available, as much as needed, for as long as possible, for the elimination of onchocerciasis as a public health problem in all endemic countries [8,9]. The permanent availability of this drug enabled the implementation of this second control strategy in a number of endemic countries in Central, East, and West Africa under the management of the African Program for Onchocerciasis Control (APOC), and in Latin America through the Onchocerciasis Elimination Program for the Americas (OEPA) [7-10]. The APOC adopted the Community- Directed Treatment with Ivermectin (CDTI) as a core strategy to treat affected populations with the objectives to (1) establish a mechanism for sustained delivery of an annual dose of ivermectin to the entire eligible populations in meso- and hyperendemic communities [11], and (2) control the disease as a public health problem in all endemic areas [7-12]. APOC supported this strategy between 1995 and 2015 and has mainly led to the reduction of prevalence and transmission to a point where onchocerciasis is no longer a public health or a socio-economic concern in several endemic foci in West Africa and even the interruption of its transmission [13-16].

Despite the progress achieved by this control strategy, persistent microfilaridermia (microfilariae in the skin) and transmission have been reported after 15-20 years of ivermectin treatment in some endemic foci in Africa [17-20]. The reasons supporting the persistence of the disease include (1) low percentage of the eligible population participating in CDTI [21], (2) existence in targeted CDTI communities of individuals who never or rarely take ivermectin so-called systematic non-compliers [22-24], (3) abundance and diversity of vector species [18-25], (4) ongoing transmission of the disease in low transmission areas, previously described as “hypo-endemic” and not included in the APOC [26] and (6) co-endemicity of loiasis in onchocerciasis transmission areas in equatorial rain forest regions of Central and West Africa [27,28]. Considering the 2021-2030 roadmap on Neglected Tropical Diseases [29]. The elimination of onchocerciasis may be accelerated and achievable by combining CDTI with Complementary Strategies (CSs) such as vector control, enhanced CDTI, community-directed treatment with drug combinations or new drugs, and Test-and-Treat (TNT) [30]. Regarding vector control, several compounds of chemical (e.g temephos, chorophoxim carbosulfan and permethrin) and biological (Bacillus thuringiensis H-14 (Bt-14)) origins have been tested and approved for Simulium larval control [31]. Although effective for the control of blackflies, these compounds are restricted for research activities because their high cost makes their procurement and use difficult on a large scale. However, physical methods, also known to be effective and less expensive, have been used since ancient times to fight a number of vector- borne diseases [32]. Physical methods of vector control are an integral part of hygiene and sanitation nowadays strongly recommended for prevention of VBDs in human communities [33].

As part of the fight against intermediate hosts (molluscs) or disease vectors (flies or mosquitoes), physical vector control consists of destroying the IH or vector breeding sites or implementing strategies avoiding human vector/IH contact. As part of the fight against the onchocerciasis vector, physical control is a community sub-directive intervention involving community volunteers in removing floating vegetation, dead leaves and woody supports harbouring eggs and larvae in Simulium breeding sites. This community-directed vector control is used to supplement mass drug distribution in the framework of onchocerciasis elimination and has proven to be effective in Uganda (East Africa) and has resulted in a significant reduction in the blackfly population density [34]. Although the results of this vector control approach appear convincing, many lessons remain to be learned for its efficient implementation in various epidemiological contexts. Moreover, the ownership and sustainability of this vector control strategy in endemic communities remains to be demonstrated. This paper presents the impact of the « Slash and Clear » vector control strategy for onchocerciasis elimination and perspectives of its ownership and sustainability in the Pouth Kelle community (Centre Region of Cameroon).

Site and Period of the Study

The study was conducted over 24 consecutive months between January 2021 and December 2022 in Pouth-Kelle community (3°30’32 “N; 10°29’26 “E; 322 m) located in the Eseka Health District in the Nyong et Kellé Division, Centre region of Cameroon (Figure 1). In 2005, the community numbered 247 individuals [35], but with the annual demographic growth rate of ≈ 2.6%, it now has almost 402 inhabitants, 95% of whom are indigenous Bassa; the rest of the population is composed of Bulu, Ewondo and Etôn, Ngoumba and Bamilékés. This community is situated in the equatorial zone, under the influence of the Guinean equatorial climate with two dry seasons (December- February and July-August) and two rainy seasons (March-June and September-November). The area is a relatively rain-deficient zone, with an average annual rainfall of around 1,500 mm and mean annual temperature of around 25°C, with relatively small temperature variations [36]. The Nyong and its tributary La Kelle are main watercourses that make up the hydrographic network of the division, whose name “Nyong et Kelle” derives from the two rivers. In some sections of these rivers, there are waterfalls, rapids and cascades that are suitable for the develo

Study Design

The study was carried out on a section of approximately 3 km of the river La Kelle running alongside the Pouth-Kelle community. This section was chosen because of the high turbidity of water and its closeness to the community. Entomological prospections were carried out on this section in order to identify blackfly breeding sites and confirm the presence of Simulium larvae. Four equally distant points situated along the 3 km were selected for adult blackfly collection. At these points, antropophilic female blackflies were collected by « Human Landing Catch » method during 3 consecutive days each month over the 24 months of the study. Indeed, the Human Landing Catch (HLC) method is known as a standard technique for insect collection; it is a procedure whereby a human volunteer sits on a low chair with bare legs and collects blackflies that land on his legs before they bite using a mouth aspirator [37]. Collections were performed by trained community volunteers between 7:00 am. and 5:00 each day. At each of the four points selected, blackflies were collected by a pair of volunteers, one working between 7:00 am and 12:00 pm and another between 12:00 pm and 5:00 pm. To avoid biases due to the collectors’ attractiveness, catching skills and the daily density of blackflies in the collection points, collectors rotated among collection points. The blackflies collected each day were counted progressively at regular 2-hour intervals and then subjected for dissection to assess the parity and infectivity rates. In addition to the entomological data collection, the physical destruction of larval breeding sites i.e. S&C was conducted every month during 2022.

Figure 1: Map showing the location of the study site (Pouth-Kelle) and the river La Kelle.

Implementation of the « Slash and Clear » Vector Control Strategy

At the end of the first year (2021) of adult blackfly collection, volunteers aged 25-50 years living permanently in the community were recruited and trained to carry out activities related to the implementation of the S&C. These activities consisted of identifying (1) Simulium breeding sites, (2) egg- laying supports and (3) blackfly larvae and pupae. During the monthly implementation of the S&C, volunteers were posted at identified breeding sites to cut and remove floating vegetation, dead leaves and pieces of wood targeted by female blackflies for egg-laying. The potential egg-laying supports were removed carefully and thrown in specific sites at the river banks for organic decomposition. The working materials and equipment included life-saving jackets, cutlasses, limes, boots, gloves, protective goggles and brushcutter machines.

Survey on Ownership and Sustainability of the S&C Vector Control Strategy

The survey on the ownership and sustainability of activities related to the S&C vector control strategy by community members was evaluated at the end of the two-year study period. This was done by collecting information from community members through Face-to-Face Interviews (FFI) or Focus Group Discussions (FGD). Participants involved in this survey were both sexes aged 18 years and above, permanent residents in the community. Before starting the FFI and FGD sessions, participants provided verbal consent to participate and authorized the research team to record all audio discussions. The interview guide used for both FFI and FGD was a questionnaire consisting of 37 opened questions grouped into three parts including (1) general information about the participants (name, age, sex, occupation, ...), (2) knowledge on the local vector borne-diseases and (3) clinical signs of onchocerciasis and (4) information on insect vectors of diseases and the vector control measures or products used for personal or collective protection. A total of 3 discussion groups of 15 to 20 individuals were formed for the collection of opinions, the first all-male, the second all-female and the third mixed. Before lunching discussions, an identifier consisting of a number from 1 to 20 was assigned to each participant. When a question was asked to the assembly, the participant wishing to answer would state his identity using the code allocated to him before providing an answer to the question. The FFI and FGD were conducted until saturation of participants’ comments was achieved.

Data Analysis

Data on fly collections and dissection during the two years of the study were recorded in an Excel file, then exported to R software for detailed analysis of (1) monthly numbers of blackflies collected (2) reduction rates in the number of bites in 2022. As the Monthly Biting Rate (MBR) is associated with the number of flies caught per month, it has been calculated as the total number of blackflies collected in the month divided by the number of days of collection for each month multiplied by 30. The Annual Biting Rate (ABR) was calculated as the arithmetic sum of the MBRs for 12 months. Descriptive statistics were compiled and presented using frequencies for qualitative variables and means associated with their standard deviations for numerical variables. The non-parametric Spearman correlation test was used to assess the relationship between rainfall distributions. Similarly, non-parametric Wilcoxon tests were used to compare central tendency indicators. The Reduction Rate (RR) in the number of bites per person per month following the destruction of breeding sites was determined using data collected in baseline 2021 and follow-up 2022. It was calculated according to the following formula : RR (%) = (NBB – NBF/ NBB) × 100, where NBB is the number of bites received per month during the baseline survey, NBF number of bites received per person per month during the follow-up survey.

The recordings of FFI and FGD were directly transcribed to english by hired translators. The transcripts were coded and analyzed in MaxQDA software v. 18.2.3 (VERBI Software. Consult. Sozialforschung. GmbH, Berlin, Germany) [38]. Demographic survey data were entered into Microsoft Excel, randomly spot- checked, and descriptively analyzed. The FFI and FGD data were analyzed using thematic analysis [39]. Transcripts were reviewed and memos written to record first impressions of the data. Data were then coded and analyzed using a “bottom-up” inductive approach [38]. Themes that were aligned with the research questions were selected and analyzed further.

Entomological Data

A total of 10,599 adult female blackflies were collected over the 24 months of the study period, including 9,163 specimens between January and December 2021 before the « Slash and Clear » intervention and 1,436 from January to December 2022 during the S&C intervention. Data obtained over this study period are summarized in (Table 1). During the first year of baseline data collection (2021), the Monthly Biting Rates (MBRs) varied between 5 and 8,545 bites/person/month, the lowest value being recorded in August and the highest in April ; the annual biting rate (ABR) recorded was 22,908 bites/person/year. In the second year of the implementation of S&C intervention (2022), the MBRs ranged from 23 to 1,273 bites/person/month, with the lowest and highest values recorded in July and February respectively. The corresponding ABR recorded was 3,590 bites/ person/year.

Rainfall and Simulium Vector Population Dynamics

Overall, the study area was characterised by a bimodal distribution in rainfall. This bimodal pattern was also observed in the annual blackfly population density of the study area with a high peak extending from December to June and a low peak between September and November (Figure 2). The high peak correlating with high blackfly density occurs during the long dry season (December-February) and the short rainy season (March- June) while the low peak associated with the low population density is observed during the long rainy season (September and November). In general, whether in 2021 or 2022, the local Simulium blackfly population appeared to be more abundant in the first period of the year between January and June including the long dry season and the short rainy season. The correlation between the two rainfall distributions was very strong and significant (R = 0.91; p < 0.001). The mean rainfall for 2021 was 168 mm (SD = 72.55) and that for 2022 was 173.3 mm (SD = 76.37), suggesting a slight increase in 2022. However, the difference between the two means was not significant (p = 0.5826) highlighting that rainfall has not changed over the two years.

Impact of the S&C Intervention on the Vector Population Density

The impact of the S&C strategy implemented in 2022 on the local black fly population is shown in (Figure 3). Overall, the monthly numbers of females blackflies caught or the Monthly Biting Rates (MBRs) recorded in 2021 were higher than those recorded in 2022 (p < 0.05), with however few exceptions in March, where they were comparable, and in November and December, where the trend was reversed (Table 1, Figure 3). The reduction in the number of bites recorded each month in 2022 following the implementation of S&C varied from 8% in March to 100% in June. Indeed, the S&C i.e the physical destruction of breeding sites has led to a drastic reduction in Annual Biting Rate (ABR) from 22,908 bites/person/year in 2021 to 3,590 bites/ person/year in 2022 with an annual reduction of 84.5%. Apart from the low RR (8%) recorded in March, the other RRs were above 70%. It must be highlighted that no RR was recorded in August, November and December. The median value of MBRs recorded in 2021 was 735 (Inter Quartil Range: 48.25 - 1966.25) bites/person/month and that obtained in 2022 was 156 (Inter Quartil Range: 32.5 - 478.0) bites/person/month. Both median values are statistically different (p = 0.01611), indicating that the 2021 MBRs were significantly higher than those of 2022.

Figure 2: Monthly, relative abundances, of the Simulium blackfly, population before (2021) and during, (2022) implementation of the <<< Slash  andClear vector control strategy in relation with rainfall in the Routh-Kelle community.

Figure 3: Image illustrating the implementation of the S&C vector control strategy on the river La Kelle.

Knowledge and Perception of the Community Regarding Vectors, Common Diseases and Vector Control Methods in Use

Socio-Demographic Data : A total of 98 participants living permaneltly in the Pouth-Kelle community were recorded for FFI and FGD. Of these, both male and female genera were represented at equal proportions (50%). The mean age of the study participants was 42 years, with the youngest and oldest being 18 and 90 years respectively. The level of education among participants varied from basic/primary to higher education, with 50% having primary education, 38% secondary education and 4% higher education. Only a tiny proportion corresponding to 8% did not have any of the above cited educational levels.

Common Diseases Affecting Human Population and Local Vector Control Methods: When participants were interviewed about the most common diseases affecting human health in the Pouth-Kelle community, 8 affections were cited among diverse responses provided during FFI (Figure 4). Vector-borne diseases (VBDs) included malaria (97%), onchocerciasis (31%), loiasis (19%) and lymphatic filariasis (11%) were in the first statement with malaria standing on top as the main cause of morbidity in the population. The remaining other diseases i.e intestinal worms (41%), diarrhoea and vomiting (29%), amoebic dysentery (23%) and schistosomiasis (1%) were related to hygiene and poor sanitation. Regarding onchocerciasis, the frequencies of its clinical manifestations reported by participants are shown in (Figure 5).

On the whole, the cited clinical manifestations were classified into two groups including skin and ocular lesions. Of the participants who reported skin lesions, 58% mentioned itching/ pruritis, 29% white marks on the skin or skin depigmentation (leopard skin), 3.6% evoked dry and crusty skin (lizard skin) while 4.8% nodules/kysts. For those who reported ocular lesions, 26% mentioned decreased of vision and highlighted 4.8% loss of vision. Concerning vector-borne diseases, all participants reported the presence of blackflies both in dry and rainy seasons, 98% mentioned mosquitoes including Anopheles, Culex, and Mansonia, 92% reported yellow flies (Chrysops spp) and 7.7% cited Culicoides. Apart from night biting insects belonging to Anopheles, Culex and Mansonia genera, for which 60% of participants said they had received mosquito nets, no other mass vector control strategy has been deployed for the entire community. In terms of personal protection, and particularly against daytime active insects (blackflies, yellow flies, culicoides) 37.7% of participants reported the use of long-sleeved clothing, 10.2% mentioned fly swatter and 19.4% mentioned the use of lemon juice or extracts, palm oil and gasoil (Figure 6).

Ownership and Sustainability of the S&C Vector Control Strategy in the Pouth-Kelle Community

Concerning the sustainability and ownership of the S&C strategy for the blackfly control, participants expressed diverse opinions. For the majority (84%), the main reason in supporting the sustainability of this vector control strategy was to avoid blackfly bites in the community. Other reasons consisted in eliminating onchocerciasis (26%), exploiting the river banks for agricultural purposes (28%) and for others the main raison was to earn money (10%). Of the residents surveyed about the ownership of the S&C, 91% requested support of the research team in sustaining the project’s activities and only 9% agreed to take over these activities with the support of the village development committee. In a FGD, participants said “We want the research team and local volunteers to sustain the tested vector control strategy till the elimination of blackflies ».

Figure 4: Monthly dynamics, of the Simulium blackfly, population before (2021) and during (2022) the implementation of << Slash and Clear vector control strategy associated to monthly percent reductions in biting rates recorded in 2022.

Figure 5: Common diseases reported by residents in the Pouth-Kelle community.

When the question of ownership of the S&C by the community was addressed to the volunteers who worked with the research team in implementing the strategy, almost all of them expressed reservations about working without any incentive: “ We work for the well-being of the community, but the other members of the community must find a way to materially and financially incentivize the volunteers. “, they said. Regarding the motivation of the team performing the S&C vector control strategy at the level of the surveyed community, 83% of participants agreed with the initiative and 13% disagreed. Those who approved the initiative promised several types of contribution including physical assistance (72%), material donation (48%), food and local drink so called matango (13%) and financial contribution (3.8%).

Figure 6: Clinical manifestations of onchocerciasis, reported by residents living permanently, in the Pouth Kelle community.

The physical destruction of Simulium breeding sites explored in this study has shown a significant reduction of the blackfly population density in the Pouth-Kelle community (Eseka Health District). The monthly differences in blackfly abundances (i.e monthly biting rates) observed over the study period reflect the seasonal variations to which our study area is subjected. Indeed, several insect populations exhibit seasonal patterns in their abundance according to climatic variables such as rainfall and temperature [40-42]. Results obtained in this study show that rainfall has an influence on the local Simulium blackfly population. Indeed, blackfly population density is higher when rainfall is moderate and lower during heavy rainfalls. This observation is in line with previous findings demonstrating that, rainfall is among the key factors regulating the dynamics of blackfly populations in certain areas of Africa [43-45], supporting that heavy rainfall correlates with low relative abundances of Simulium blackflies as reported earlier in other African countries [44-46]. Although favorable for the up-mixing of water and the production of oxygen for aquatic organisms, heavy rainfalls may contribute to effective drainage, complete immersion and leaching of Simulium breeding sites. This phenomenon negatively affects the Simulium population density during heavy rains resulting in a low relative abundance of adult blackflies in the terrestrial environment.

The annual dynamics of the surveyed blackfly population showed a similar trend over the two years of the study, suggesting that the climatic conditions have not significantly varied at the zonal scale over the 2 years of the study. However, compared to year one, the low relative abundances of flies observed during the second year of the study reflects the impact of S&C implemented at monthly frequency in the study area. These results are in agreement with the recent literature on physical destruction of larval breeding sites using the S&C approach [34-48]. However, it should be underlined that the effectiveness of “Slash and Clear” vector control strategy as explored in this study depends on the following components namely (1) the flow of the watercourse, (2) the frequency of intervention, (3) the season and (4) the ecological environment. The reduction rates in the number of bites reported in this study conducted in a medium-flow river are very interesting (70-100%) compared with those reported in a high-flow river in the Bafia Health District [49]. This result suggests that the accessibility of larval breeding sites is the main component to be considered in implementing effective S&C approach. In fact, free access to Simulium breeding sites as noted in the targeted medium-flow river (La Kelle) enables efficient implementation compared to hard-to reach breeding sites observed in a high-flow river (e.g Mbam in Bafia) which keep part of the immature fly population growing, then rebuilding the overall population after the implementation of the S&C approach.

The low reduction rate in the number of bites reported in March 2022 has been a valuable information leading to understand that the frequency in implementing the S&C in a given environment is an important component to be considered. In the framework of this study, the S&C was previously planned for a quarterly implementation. This low reduction rate (8%) led to shorten the frequency from quarterly to monthly implementation, indicating that a long period (? 1 month) between 2 successive S&C implementations is critical to the success of this strategy in the local environment. In fact, the implementation frequency over a long period may allow the growth of the riparian vegetation considered as potential aquatic supports targeted by female Simulium blackflies for oviposition. In addition to this fast-growing vegetation, external inputs containing pieces of wood and dead leaves drained into the river by run-off water are potential egg-laying supports for blackflies. These observations are in agreement with previous findings reported in South Sudan indicating that the feasibility and efficacy of the S&C method may depend on local vegetation and other riverine features [47]. The lack of reduction in the number of bites observed during the months of August, November and December may be explained by the variation in the flow of water and the assiduity of the community members in carrying out the S&C. Indeed, the drop in water flow reduces the width of the river and consequently the change in the topography of the breeding sites. This explains why the locations of breeding sites during the rainy season are different from those of the dry season in the same river section.

The common diseases mentioned by the participants in this study are part of the list of diseases drawn up by the WHO as being the diseases related to water and environmental sanitation [29]. These diseases are classified as poverty-related diseases [49], reflecting the health and socioeconomic situation of the Pouth-Kelle community as many others in low-income countries in sub-Sahara Africa. The description of the clinical signs of onchocerciasis by the participants suggests that this affection is well known by the populations. The knowledge of the epidemiology, clinical manifestations and the transmission patterns of onchocerciasis in endemic communities have been improved with the implementation of CDTI, during which community distributors raise awareness to the local population during ivermectin mass distributions campaigns. As for the ownership of the S&C strategy by the community and its sustainability for the control of onchocerciasis vectors, our findings suggest that deploying this approach in surveyed community remains a stumbling block in the fight against onchocerciasis. The fight against onchocerciasis through this strategy relies on community participation and engagement. It is worth recalling that community participation or engagement is defined as a beneficial relationship between the community stakeholders and primary healthcare system and professionals on a wide range of tasks, their role in decision-making and their participation in decision-making to improve the health of the community [50].

In the context of this study, the community may wrongly consider that this is a unilateral relationship, whereas it is a bilateral relationship which involves the community and the healthcare system with its professionals. View as such, our investigations do not lead to a conclusion that the ownership and sustainability of the S&C strategy are not achievable in the Pouth-Kelle community. It is important that the vector control method tested in the framework of this study must be approved by decision-makers and recommended where applicable as part of the control of onchocerciasis vectors in endemic areas. Once this step has been completed, additional trials will be needed to evaluate the community engagement to this vector control strategy. Apart from rainfall, no other parameter (e.g: flow rate of the watercourse) that could influence the density of the sampled blackfly population was investigated during the 2 years that made up the period of our study. This could be among others the limitation for this study. However, data presented in this paper are very important in guiding and establishing vector control at the community level in onchocerciasis endemic areas.

This study demonstrated that the S&C implemented by the members of the community is effective for the control of onchocerciasis vectors in a medium-flow stream when all the implementation conditions are met. This approach appears as a potential complementary vector control strategy to combine to ivermectin mass distribution for the elimination of onchocerciasis in the community of Pouth-Kelle. In addition to its crucial importance in high loiasis endemicity areas, the S&C may be included among candidate complementary strategies to ivermectin in onchocerciasis-endemic areas. Its ownership and sustainability in endemic communities, healthcare system and its professionals remain to be investigated. The data provided in this study are useful for the Ministry of Public Health in refining and redirecting the strategy for eliminating onchocerciasis in Cameroon.

The authors are grateful to the Regional Health Delegate of the Centre region, all health staff at District and health area levels, the traditional chiefs and their respective populations for their active involvement for data collection in the field.

Funding

The financial activities of this study was supported by Task Force Glbal Health.

Ethical Approval

The study was approved by the National Committee on Ethics in Human Science Research under number N° 2020/03/1208/ CE/CNERSH/SP of March 09, 2020).

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