A bovine serological survey of foot-and-mouth disease in the northern communal area of Namibia

Abstract

Foot-and-Mouth Disease (FMD) is a disease of cloven-hoofed animals well-known not only for significant production losses but also restricted market access for livestock and livestock products from affected areas. It severely limits market opportunities for poor farmers and nations wishing to access more lucrative markets, both regionally and internationally. In the Northern Communal Area (NCA) of Namibia, FMD has not been detected in Kunene, Omusati, Oshana, Oshikoto and Ohangwena regions for the past 45 years or more, while outbreaks occurred in Eastern Kavango towards the end of 2008 as well as beginning of 2009 and there have been frequent outbreaks in the Zambezi region. Although, FMD has not been detected in five of the six regions of the Namibian NCA, no studies have been carried out to substantiate the FMD status in this highly potential livestock production area as required by the World Organisation for Animal Health (OIE). It is based on this fact that a study was carried out in the above mentioned regions to determine whether there is Foot-and-Mouth Disease Virus (FMDV) circulating in the cattle population of the NCA Namibia. A set of 4214 serum samples were taken from non-vaccinated animals against FMD in Area A, which included Kunene north, Omusati south, Oshikoto(NCA) and Oshana. Meanwhile, 5228 serum samples were taken from Area B, which consisted of Omusati north, Ohangwena and Kavango region where cattle had been vaccinated against FMD for the past 15 years or more. Samples were primarily screened for FMDV using the Ceditest® NSP ELISA and positive samples were subsequently tested with the Viral Neutralization Test (VNT). Herds containing animals that were positive on both tests were followed up and retested with the Ceditest® NSP ELISA and examined clinically for FMD signs. The initial results of the Ceditest® NSP ELISA in Area A and B revealed an apparent prevalence of 0.24% and 0.27% with corresponding 95% confidence intervals between 0.13, 0.44 and 0.16, 0.45 respectively. The follow up results found no clinical evidence of FMD and all subsequent Ceditest® NSP ELISA results were negative. The results indicate that the initial Ceditest® NSP ELISA positive cattle were false positive. Thus the overall outcome indicates that there is little chance of FMD virus circulation in the NCA Namibia. The survey also highlighted the need for taking into account sociological and cultural practices when designing a survey of communal cattle in order to get a representative sample of the cattle population. The study also recommended that Directorates of Veterinary Services (DVS) Namibia should maintain and continuously review FMD surveillance activities in the NCA, especially along the Angola – Namibia border and continuously harmonise these activities with Angolan counterparts. A more comprehensive study should be carried out to address the insufficient knowledge on sociological factors, which may influence sampling strategies in communal farming areas.