Foot-and-mouth disease transmission measured in Cameroonian cattle reveals stark regional contrasts

Foot-and-mouth disease (FMD) virus circulated intensively in two contrasting cattle-rearing areas of Cameroon, with a new cross-sectional serological study estimating that more than half of all cattle in the Vina Division of the Adamawa Region carried antibodies indicating past infection, compared with roughly four in ten animals in the North-West Region. The findings, based on 1,498 animals sampled from 100 herds in 2013, provide rare empirical estimates of key transmission parameters in an endemic setting and highlight how much local disease dynamics can differ within a single country.

The research, conducted by a team from the Roslin Institute at the University of Edinburgh together with partners at The Pirbright Institute, the University of Buea, the University of Ngaoundere, the University of Liverpool, Cameroon Academy of Sciences and Canada’s National Centre for Foreign Animal Disease, was published in Frontiers in Veterinary Science. The team analysed biobanked serum samples collected during a survey originally designed to study bovine tuberculosis, screening them for antibodies against the foot-and-mouth disease virus non-structural protein 3ABC using a competitive ELISA. Because these antibodies are produced only during viral replication, their presence indicates true exposure to infection rather than a response to vaccination, a distinction that proved important as no FMD vaccination program was in operation and farmers could not access FMD vaccines in Cameroon at the time of the study.

The two study areas, each roughly 17,000 square kilometres, differ markedly in landscape, human population and husbandry. The North-West Region lies in Cameroon’s mountainous highlands, is densely populated with more than 1.8 million people including many non-cattle-keeping groups, and holds an estimated 506,548 cattle. The Vina Division sits on the Guinea savannah plateau of the Adamawa Region with a far smaller human population of 317,888 people, dominated by cattle keeping, and an estimated 176,257 cattle. Cattle-keeping populations also differ culturally: herders in the North-West, identifying as Mbororo, are traditionally more nomadic, with around 44 percent of herds undertaking transhumance, compared with only about 6 percent among the predominantly sedentary Fulbe of the Vina Division.

Herdsmen’s own accounts reflected widespread recent disease. In the North-West Region, 60.1 percent of herdsmen reported animals with clinical FMD within the previous 12 months, rising to 76.8 percent in the Vina Division. Notably, 32.9 percent of herdsmen in the North-West attributed deaths to FMD, compared with 17.1 percent in the Vina Division, a difference the authors suggest could reflect different serotypes or strains with distinct epidemiological characteristics. Previous work had identified serotype A circulating in the North-West Region in 2012 and serotype SAT2 in the Vina Division.

Serological evidence told a consistent story. Using an empirically derived ELISA cut-off of greater than 40 percent inhibition, chosen after examining the observed antibody distributions rather than the manufacturer’s 50 percent threshold, the design-adjusted animal-level seroprevalence was 38.2 percent (95 percent confidence interval 31.3 to 45.8) in the North-West Region and 56.7 percent (47.8 to 65.2) in the Vina Division. Antibody levels rose steeply with age up to about four to five years before plateauing, a pattern characteristic of endemic infections in which susceptible animals are progressively infected until most of the population has been exposed. At the divisional level, seroprevalence exceeded 50 percent in areas such as Bui and Ngoketunjia in the North-West and in most sub-divisions of the Vina Division, reaching 78 percent in Ngoketunjia and 80 percent in Mbé, although the small sample in Mbé carried high uncertainty.

From these age-stratified data, the team estimated the force of infection, the rate at which susceptible animals become infected, using three competing models compared by Akaike’s Information Criterion. Assuming constant force, infection rates were almost twofold higher in the Vina Division (0.382) than in the North-West Region (0.197). The best-fitting models in both sites allowed the force of infection to decline with age, suggesting that younger animals experience more mixing and transmission, potentially through movements, sales and seasonal migration. The derived basic reproduction number, R0, the average number of new infections one infected animal would generate in a fully susceptible population, was estimated at 2.05 (95 percent CI 1.93 to 2.18) in the North-West Region and 3.04 (95 percent CI 2.84 to 3.26) in the Vina Division, assuming an average cattle life expectancy of six years. These values fall within the published range for FMD elsewhere, which spans from below 1 to over 13 with a median of roughly 1.7.

A crucial reversal emerged when the researchers accounted for existing population immunity and test performance to calculate the effective reproduction number, Rt. Despite the Vina Division’s higher R0, its greater immunity pushed Rt down to 1.14 (95 percent CI 1.02 to 1.22), below the 1.23 (95 percent CI 1.15 to 1.30) estimated for the North-West Region, where a larger susceptible fraction sustained comparatively higher ongoing transmission risk. This inversion illustrates, the authors argue, why control planning cannot rely on R0 alone: interpreting current transmission risk and targeting interventions requires accurate knowledge of how much immunity a population already holds.

The estimates also expose the difficulty of achieving control through vaccination alone. The critical vaccination threshold, calculated as 1 minus 1 divided by R0, was 51 percent in the North-West Region and 67 percent in the Vina Division. Because estimated immunity, reflected by seroprevalence, stood at only 38.2 percent and 56.7 percent respectively, both populations remained below the level needed to interrupt transmission, consistent with Rt exceeding 1 in both sites. The shortfall was proportionally larger in the North-West, suggesting a comparatively greater gain in immunity would be needed there. Sustaining such coverage would demand well-matched vaccines and repeated campaigns, a considerable logistical and financial challenge for Cameroon’s veterinary services.

Risk-factor modelling identified age, region and seropositivity for bovine viral diarrhoea (BVD) as independently associated with FMD seropositivity. Compared with young animals, adults had nearly tenfold higher odds and animals older than five years about thirty-four-fold higher odds of being seropositive; animals from the Vina Division had 3.45-fold higher odds, and BVD-seropositive animals 1.54-fold higher odds. The BVD association may reflect immunomodulation, but the authors consider it more likely to be a marker of animals embedded in highly connected production systems with frequent movements, trade and contact at communal grazing and watering points, the same mechanisms known to facilitate FMD transmission. In univariable analyses, shared watering points and recent cattle purchases were strongly associated with infection, while apparent protective associations with transhumance and buffalo contact disappeared after confounding, particularly by study area, was accounted for. The role of African buffalo, reservoirs of SAT serotypes elsewhere in Africa, in maintaining transmission in Cameroon remains uncertain.

The authors caution that the analysis carries inherent limitations of cross-sectional design. Transmission dynamics were inferred from age-specific antibody patterns rather than observed directly over time, and the estimates represent a temporal average across periods of higher and lower transmission intensity over the sampled animals’ lives rather than real-time dynamics. Age estimates relied partly on field assessment and may be misclassified, particularly in older animals, and the questionnaire was not designed for FMD investigations, lacking detail on movement frequency, market attendance and biosecurity. Serotype-specific data were also unavailable, a major limitation given that different serotypes may drive different transmission rates. Nevertheless, the consistency between serological patterns, force-of-infection estimates and epidemiological observations gives the team confidence that the findings capture genuine features of FMD transmission in endemic cattle populations, and they argue that studying FMD where multiple serotypes co-circulate, in partnership with endemic countries, offers enormous potential for understanding viral transmission, evolution and the risk to FMD-free regions.

Subject of Research: Seroprevalence, risk factors and force of infection of foot-and-mouth disease in cattle in two regions of Cameroon

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

Article References: Bronsvoort, B. M. D., Limon, G., Ndip, L., Tanya, V. N., Morgan, K. L., Ngu Ngwa, V., Nfon, C. K., Kelly, R. F., van Bunnik, B. A. D., & González Gordon, L. (2026). Sero-prevalence, risk factor and force of infection estimates for foot-and-mouth disease in two cattle rearing areas of Cameroon. Frontiers in Veterinary Science, 13, Article 1959956. https://doi.org/10.3389/fvets.2026.1959956

Image Credits: AI Generated

DOI: 10.3389/fvets.2026.1959956

Keywords: foot-and-mouth disease, Cameroon, cattle, seroprevalence, force of infection, reproduction number, veterinary epidemiology, FMDV, transboundary animal disease, vaccination, Sero-prevalence, risk