Immunohistochemical detection of foot-and-mouth disease virus in carrier African buffalo (Syncerus caffer)

Abstract

BACKGROUND : African buffalo are long-term carriers of foot-and-mouth disease virus (FMDV), particularly the South African Territories serotypes. Detecting low viral loads in carrier animals remains challenging. OBJECTIVES : This study aims to detect FMDV antigen in formalin-fixed tissues of carrier buffalo using immunohistochemistry (IHC) to identify potential sites of viral persistence. METHODS : Polyclonal antibodies targeting structural FMDV proteins were used to detect FMDV in formalin-fixed tissues from African buffalo (n = 15) culled in the Kruger National Park. The results were scored and compared with those from polymerase chain reaction (PCR). RESULTS : Viral antigen was consistently associated with the vasculature of the coronary band and interdigital skin as well as in the lungs. It was also associated with the germinal centres of the palatine tonsils. Detection outside these areas was rare, indicating a distinct tissue tropism favouring the vasculature in carrier animals. All buffalo tested IHC positive, including some PCR-negative cases, suggesting IHC may offer increased sensitivity when viral loads are low. CONCLUSIONS : The results revealed a novel association of viral antigen with vascular tissue and demonstrated the potential for superior sensitivity over PCR. Further research is needed to validate this assay, prove repeatability and clarify how carriers contribute to disease persistence and transmission.