Point prevalence mapping reveals hotspot for onchocerciasis transmission in the Ndikinimeki Health District, Centre Region, Cameroon

Abstract

Background 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. Methods 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. Results 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, df = 11, P = 0.0001). 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%). Conclusions This study has revealed that the Ndikinimeki Health District is hypo-endemic for onchocerciasis after about two decades of preventive chemotherapy. However, transmission is ongoing, 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.

Individual longitudinal compliance to neglected tropical disease mass drug administration programmes, a systematic review

“…Two longitudinal studies asked respondents to recall their previous treatment behaviour at each round, over six annual rounds in Ethiopia for trachoma (34), and over 10 annual rounds in Nigeria for onchocerciasis (35). Three cross-sectional studies asked participants to recall their treatment behaviour during MDA for onchocerciasis over a specific time period, either five annual rounds (40) and 11+ annual rounds (36) in Cameroon, or 10 biannual rounds in Ethiopia (42). Two of these studies referred to compliance in line with the definitions considered for this review (40, 42).…”

“…Three cross-sectional studies asked participants to recall their treatment behaviour during MDA for onchocerciasis over a specific time period, either five annual rounds (40) and 11+ annual rounds (36) in Cameroon, or 10 biannual rounds in Ethiopia (42). Two of these studies referred to compliance in line with the definitions considered for this review (40, 42). A further two cross-sectional studies asked participants to recall ever being treated during MDA for lymphatic filariasis in Ghana (37, 38).…”

“…Specifically, compliance to treatment increasing with age was reported by Osei et al (2022) (53) (AOR 4.23 (95% CI: 0.84-21.19), adults aged >58, compared to 18-27 year olds), and Chisha et al (2020) (56) (AOR 1.45 (95% CI: 1.25-1.69), SAC aged 10–14, compared with to 5-9 year olds). Aza’ah et al (2020) (57) presented this phenomena via Chi-squared statistics, noting the proportion of age groups complying with MDA increased from 22.6% (95% CI: 16.3–30.4%) of 10-19 year olds, to 60.3% (95% CI: 53.1–67.1%) of participants aged ≥ 50 years (χ 2 = 64.1, df = 3, P < 0.0001), as did Minetti et al (2019) (38), who noted MDA participation increased with age (χ 2 = 8.75, df = 1, p = 0.003). Mirroring this, Kifle and Nigatu (2021) (42) noted low compliance in young age groups, (AOR 0.68 (95% CI: 0.77-1.76) young adults aged 15-24 years, compared to >45 year olds).…”

Immunoinformatics Design and Assessment of a Multiepitope Antigen (OvMCBL02) for Onchocerciasis Diagnosis and Monitoring

“…Assessment of the geographic distribution of onchocerciasis in Cameroon revealed that onchocerciasis is endemic in all the ten regions of Cameroon with approximately 60% of the population living in high-risk areas for the disease [ 31 ]. Furthermore, assessment of communities which have been receiving preventive chemotherapy for close to 20 years revealed the continuous spread of the parasite in some communities [ 51 , 52 ]. The OvMCBL02 test is an antibody-based test which is unable to differentiate between past and current infection; thus, control samples were obtained from Rwanda and Europe rather than Cameroon to exclude the possibility of including healthy individuals that may have been infected with the parasite in the past.…”

Prevalence of Onchocerciasis Infection in the Sub-Saharan Africa Countries: A Systematic Review and Meta-analysis

“…20 In conclusion, the findings from various of the African continent is fragmented, not informative and a wide range of prevalence of onchocerciasis infection: they were reported ranging from 6.32% to 17% in Ethiopia. [21][22][23] 2.43% to 13.2 in Ghana, 24 1.7% to 23.7% in Uganda, 25 7% to 19% in Cameron, [26][27][28] 5% to 73% in Côte d'Ivoire and Burkina Faso, 29 49% to 83.2% in Tanzania. 30 Therefore, understanding the pooled prevalence of onchocerciasis infection is paramount to design sound preventive and control strategies targeted to eliminate and eradicate the newly appearing infection in the region.…”