Serotype Characterization and Transmission Modelling of Foot-and-Mouth Disease in Dairy Farms, Bishoftu, Ethiopia

Foot-and-mouth disease (FMD) is among the most important transboundary animal diseases, causing widespread economic losses due to decreased productivity, trade restrictions, and costly disease management efforts.

This study aimed to characterize circulating FMDV serotypes and quantify within-farm transmission dynamics during active outbreaks in Bishoftu, Ethiopia.

Five epithelial tissue and 39 oral swab samples were collected from 11 dairy farms experiencing active FMD outbreaks. Samples were tested using quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) and antigen-capturing enzyme-linked immunosorbent assay (ELISA) for FMDV detection and serotyping. A susceptible-infected-recovered (SIR) model was fitted to outbreak data to quantify transmission dynamics.

Out of 44 samples, 37 (84.1%) were positive for FMDV using RT-qPCR, and 23 (52.3%) were positive by ELISA. Serotypes O, SAT-1, and SAT-2 were identified, with SAT-2 being predominant. Transmission modelling indicated an average transmission rate (λ) of 0.82 and a recovery rate (γ) of 0.32 per day, corresponding to a mean basic reproductive number (R₀) of 3.7. The trivalent vaccine demonstrated low effectiveness (31% against single serotypes; 26% when adjusted for mixed infections), which was insufficient to achieve herd immunity given the high transmission intensity.

These findings demonstrate that vaccination alone cannot control FMD in these systems. Control requires improved vaccine matching and the combination of vaccination with enhanced biosecurity measures, such as animal isolation and movement control.