Abstract
Foot and mouth disease (FMD) burden disproportionally affects Africa where it is considered endemic. Smallholder livestock keepers experience significant losses due to disease, but the dynamics and mechanisms underlying persistence at the herd-level and beyond remain poorly understood. We address this knowledge gap using stochastic, compartmental modelling to explore FMD virus (FMDV) persistence, outbreak dynamics and disease burden in individual cattle herds within an endemic setting. Our analysis suggests repeated introduction of virus from outside the herd is required for long-term viral persistence, irrespective of carrier presence. Risk of new disease exposures resulting in significant secondary outbreaks is reduced by the presence of immune individuals giving rise to a period of reduced risk, the predicted duration of which suggests that multiple strains of FMDV are responsible for observed yearly herd-level outbreaks. Our analysis suggests management of population turnover could potentially reduce disease burden and deliberate infection of cattle, practiced by local livestock keepers in parts of Africa, has little effect on the duration of the reduced risk period but increases disease burden. This work suggests that FMD control should be implemented beyond individual herds but, in the interim, herd management may be used to reduced FMD impact to livestock keepers.
Highlights
Foot and mouth disease (FMD) burden disproportionally affects Africa where it is considered endemic
Our model strongly suggests that disease cannot persist without re-introduction of FMD virus (FMDV) within a single herd
We show there is a reduced average risk period following outbreaks which is typically longer than the average period between outbreaks in FMD endemic regions
Summary
Foot and mouth disease (FMD) burden disproportionally affects Africa where it is considered endemic. Smallholder livestock keepers experience significant losses due to disease, but the dynamics and mechanisms underlying persistence at the herd-level and beyond remain poorly understood. We address this knowledge gap using stochastic, compartmental modelling to explore FMD virus (FMDV) persistence, outbreak dynamics and disease burden in individual cattle herds within an endemic setting. This complicates efforts to distinguish the dynamics of the individual serotypes from the observed disease in the field. Understanding of FMD in endemic regions is largely informed by cross-sectional studies While this is beneficial for providing an overview of FMD it can be difficult to understand ongoing disease dynamics, at the herd-level. It is important to understand if this is true and whether the presence of carriers would alter advice given to herders, as vaccination does not protect against the development of carrier status[20]
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