van Schalkwyk, L. | Search bioRxiv

bioRxiv2023

Importance of wildlife in the circulation and maintenance of SAT1 and SAT2 foot-and-mouth disease viruses in Africa

Author summaryFoot and mouth disease (FMD) viruses are endemic in sub-Saharan Africa. Due to the complexity of the disease epidemiology and the lack of available data, there is a need to use phylogenetic approaches to understand the role of potential hosts involved in the circulation and maintenance of the viruses. The uneven host sampling of the available sequences requires us to take advantage of the recent advances in phylogenetic reconstruction. Therefore, using two structural coalescent model approximations we estimated the circulation of FMD virus serotypes SAT1 and SAT2 between cattle, buffalo and impala populations. Our results suggest that in Africa, the impala population seems to act as an intermediate host between the cattle and buffalo populations and play a more important role in the circulation of the viruses than was previously suspected. Until now, the role of the impala population in the circulation of FMDV has been suggested, but never explicitly shown.

molecular biology↗

bioRxiv2021

Viral dynamics and immune responses to foot-and-mouth disease virus in African buffalo (Syncerus caffer).

Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While it is clear that African buffalo (Syncerus caffer) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle inoculation and contact infections with three Southern African Territories serotypes to assess clinical, virological and immunological dynamics for thirty days post infection. Clinical FMD in the needle inoculated buffaloes was mild and characterised by pyrexia. Despite the absence of generalised vesicles, all contact animals were readily infected with their respective serotypes within the first 2-9 days after being mixed with needle challenged buffaloes. Irrespective of the route of infection or serotype there were positive associations between the viral loads in blood and the induction of host innate pro-inflammatory cytokines and acute phase proteins. Viral loads in blood and tonsils were tightly correlated during the acute phase of the infection, however, viraemia significantly declined after a peak at 4 days post infection (dpi), which correlated with the presence of detectable neutralising antibodies. In contrast, infectious virus was isolated in the tonsils until the last sampling point (30 dpi) in most animals. The pattern of virus detection in serum and tonsil swabs was similar for all three serotypes in the direct challenged and contact challenged animals. We have demonstrated for the first time, that African buffalo are indeed systemically affected by FMD virus and clinical FMD in buffalo is characterized by a transient pyrexia. Despite the lack of FMD lesions, infection of African buffalo was characterised by high viral loads in blood and oropharynx, rapid and strong host innate and adaptive immune responses and high transmissibility.

zoology↗