Development of improved foot-and-mouth disease (FMD) assays with a focus on small ruminants in southern Africa

Abstract

As an economically important livestock disease, foot-and-mouth disease (FMD) requires adequate strategies for its control. In southern Africa, FMD is endemic and threatens the livelihood of smallholder farmers who rear goats, sheep and cattle for subsistence. However, goats and sheep (small ruminants) are largely ignored in routine surveillance and vaccination campaigns in endemic areas. Furthermore, due to the occurrence of subclinical infection, they pose the risk of facilitating the silent spread of the disease to other livestock animals.

To improve the effectiveness of FMD control, established diagnostic assays should be validated/verified for use in small ruminant species in addition to the development of rapid and accurate next-generation assays. The aim of this study was to improve FMD diagnostic tests used on small ruminants and to investigate the molecular evolution of Foot-and-Mouth-Disease Virus (FMDV) in sub-Saharan Africa as a first step to future development of advanced diagnostic tools tailored to the region.

The first study optimized and verified a single-spot solid-phase competitive ELISA (ss-SPCE) for the detection of antibodies against FMDV Southern African Territories (SAT) serotypes in goats and sheep sera collected from South Africa. The second study developed and preliminarily validated a field-deployable reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of FMDV serotype SAT1 topotype II viruses. The third study explored the molecular evolution of FMDV SAT serotypes from sub-Saharan African isolates sampled between 1934 and 2022.

The optimized ss-SPCE assay successfully measured the prevalence of disease in small ruminants during an active SAT2 outbreak in South Africa. The developed RT-LAMP test was highly specific and proved to be a propitious next-generation assay for the diagnosis of SAT serotypes in southern Africa. The molecular evolution findings indicated that the SAT serotypes continue to evolve as seen with the continuous discovery of new topotypes across the continent over the years. With continued disease surveillance and outbreak investigations, the data will be beneficial to the development of tailored diagnostic tools for the region.