Modelling the impact of interventions on the optimal control of Cholera in hotspots in Uganda

Abstract

Background: Cholera is an infectious disease that is caused by eating food or drinking water contaminated with a bacteria known as Vibrio cholerae. Historically there have been seven (7) pandemics and Uganda as a country was also affected by the 7th cholera pandemic. In view of combating further outbreaks, the Government of Uganda established preventive and control mechanisms however, cholera cases continue to be reported annually. Mathematical modelling is one of the ways cholera control has been studied and optimal control strategies provided. Thus, the aim of this study is to use mathematical modelling to determine the most optimal control strategy in cholera hotspots in Uganda. Methods: This was a modelling study with model parameters obtained from literature and from existing empirical data obtained from the cholera hotspot districts in Uganda namely: Buliisa, Hoima, Mbale and Nebbi. To determine the most optimal control strategy of cholera which is cost effective using mathematical modelling, this study employed a Susceptible-Vaccinated-Infected- Treated-Recovered (SVIR-B) model to study the dynamics of the control of cholera in hotspot areas in Uganda. The study then carried out sensitivity analysis on the model parameters under the various assumptions on the level of cholera disease burden and concluded with determining the effect of combined intervention strategies of vaccination, treatment, education awareness and sanitation in the control of cholera infection. Results: The reproductive number obtained was 0.000876 < 1, the rate at which the infectives infect the environment (𝛽) was the most sensitive parameter with a value of 0.8612 and the results extended by Pontraygin’s principle showed the most optimal control strategy as a combination of vaccination, sanitation and education awareness. Findings showed that control of cholera is better when combinations of different strategies more than one are employed that is three better than two and four better than three and education awareness must always be among the combination of strategies for the infection to curl down to zero. The Incremental cost-effectiveness ratio with the lowest cost value of $72 was that of the combination of education awareness and treatment. Conclusion: Our findings suggest that any intervention strategy should include education awareness if cholera is to be controlled. The most cost effective strategy was a combination of education awareness at 97% coverage and treatment at 47% coverage. Sensitivity analysis showed that the rate at which cholera is shed in the environment was the most sensitive parameter.