Ivermectin Mass Drug Administration Coverage Against Onchocerciasis in Cameroon, 2000-2025: A Systematic Review and Meta-analysis

Persistent onchocerciasis transmission has been documented in some Cameroonian foci despite long-term ivermectin mass drug administration (MDA). We synthesized treatment coverage, adherence and determinants.

We systematically reviewed seven databases and grey literature (2000-2025). District-year coverage observations were standardized to total-population epidemiological coverage and pooled using logit-transformed random-effects meta-analysis with Restricted Maximum Likelihood estimation and study/district cluster-robust inference. Adherence, infection prevalence and barriers to treatment were described separately.

Thirty-two studies/reports were included among which 20 independent sources contributed 116 observations to the primary meta-analysis. Standardized survey coverage averaged 66.5% (range 32.0-88.3%); 45/116 (38.8%) observations were below the 65% recommendation. Programme-reported coverage exceeded survey estimates in 97/98 paired observations by a mean 21.7 percentage points. Pooled coverage was 67.3% (95% CI 65.0-69.5%; I²=98.5%; prediction interval 40.6-86.1%); the cluster-robust 95% CI was 56.8-76.3%. Five-year adherence ranged from 24% to 67%, while systematic non-adherence ranged from 6.8% to 35% across reported settings. Qualitative synthesis identified setting-specific combinations of missed contact, absence, distribution failures, refusal or hesitancy, adverse-effect concerns, information and trust barriers, mobility and temporary ineligibility. Microfilarial prevalence declined substantially from baseline (52% to 95%) but remained highly heterogeneous across long-treated settings, with the latest reported post-CDTI prevalence ranging from 0% to 47.0%.

Ivermectin mass drug administration (MDA) coverage in Cameroon was highly heterogeneous, mirroring variations in infection prevalence. Programme-reported coverage consistently exceeded survey-based estimates. Coverage gaps reflected context-specific operational and community acceptance barriers. Elimination monitoring should therefore triangulate survey-based coverage and adherence, local delivery barriers, and transmission indicators to guide targeted programme improvements and onchocerciasis elimination decisions.