Quantifying the burden of foot and mouth disease in selected districts in Uganda

Abstract

One cycle of foot and mouth disease is considered for a susceptible, infected and removed epidemiological model. Analysis of the basic properties of the SIR epidemic model with direct transmission of infection and numerical simulation when isolation and vaccination are incorporated to reflect the impact of an health strategy on the quality of life of cattle is done. Feasibility and positivity of equations of the nonlinear system are examined and Taylor's expansion is applied to solve for the size of the epidemic and sensitivity analysis carried out to explain the relative importance of parameters to FMD transmission and prevalence. The cost of mortality and mobility is used to quantify the health burden of FMD on a state of health of the cattle by calculating the DALY gain after controlling an FMD outbreak and the QALY of the cow that survives FMD. The calculations were based on data on cattle from Gomba, Butaleja, Bulisa and Tororo districts. Mean disability weight was assigned to FMD conditions of diary and lameness, musculoskeletal injury and milk fever. The numerical simulations were compared for isolation and vaccination to ascertain which intervention is more effective in reducing FMD burden. Numerical results show that the number of infectious cows increased rapidly during the first $50$ days after the epidemic. Furthermore, Bulisa district registered most DALYs per 10,000 cattle as compared to Tororo and Butaleja districts. It was observed that Butaleja had the least case fatality rate followed by Bulisa and Tororo districts. Furthermore, Butaleja had the least attack rate followed by Tororo while Bulisa registered the biggest attack rate. Results indicate that effective isolation or isolation combined with vaccination strategies aimed at minimizing contact between the infectious and susceptible cow are critical in minimizing the spread of FMD. This is so since the strategies limit the number of infectious animals which would transmit the infection. Thus, to effectively control an outbreak, the study suggests that much emphasis should rely on early detection of clinical signs from infectious animals.