Sero-prevalence, risk factor and force of infection estimates for foot-and-mouth disease in two cattle rearing areas of Cameroon

Abstract

Foot-and-mouth disease continues to be a major disease burden globally, directly impacting endemic regions and indirectly affecting free regions. There is a lack of reliable estimates of key parameters delivered from empirical field data, such as transmission rates for developing useful models to assess the impacts of control strategies to inform policies. The main objectives were to estimate the seroprevalence and risk factors of FMD in the 2 study areas, estimate the force of infection and the reproductive number, R0. A total of 1,498 cattle from 100 herds across the Northwest Region (NWR) and Vina Division (VIN) of Cameroon were sampled. Evidence of recent FMD occurrence was widespread, with 60.1% (95% CI: 45.9–73.0) of herdsmen in the NWR and 76.8% (95% CI: 62.4–87.0) in the VIN reporting clinical FMD within the previous 12 months. FMD non-structural protein (NSP) antibody responses increased with age before reaching a plateau, consistent with cumulative exposure in endemic settings. Using an empirically derived ELISA cut-off (>40 PI), the design-adjusted animal-level seroprevalence was 38.2% (95% CI: 31.3–45.8) in the NWR and 56.7% (95% CI: 47.8–65.2) in the VIN, demonstrating substantial virus circulation in both regions and significantly greater exposure in the VIN. Age-stratified analyses revealed a rapid increase in seroprevalence during the first 6–7 years of life, with force of infection estimates almost two-fold higher in the VIN (λ = 0.382) than in the NWR (λ = 0.197). Correspondingly, the basic reproduction number (R₀) was estimated at 3.04 (95% CI: 2.84–3.26) in the VIN and 2.05 (95% CI: 1.93–2.18) in the NWR, indicating sustained transmission in both areas. Risk factor analyses identified herd connectivity through shared watering points, cattle purchases, increasing age, and BVD seropositivity as significant predictors of FMD exposure, highlighting key mechanisms facilitating virus transmission. Foot-and-mouth disease is endemic in both study regions of Cameroon, with evidence of substantial transmission and cumulative exposure occurring early in life. Age-stratified serology provided robust estimates of key parameters, demonstrating markedly higher transmission intensity in the Vina Division than in the Northwest Region. It highlights the real-world complexity of estimating these parameters and the variation across different regions.