Seroprevalence of foot and mouth disease and peste des petits ruminants in small ruminants in Zambia on the border to Tanzania : Searching for common traits among seropositive herds

Abstract: Foot and mouth disease (FMD) and peste des petits ruminants (PPR) are highly contagious viral diseases affecting sheep and goats all over the world. Small ruminants are often owned by poor small-scale farmers in the developing world, and several studies have identified them to be among the most important livestock species for the poor. Controlling, or even eradicating, FMD and PPR is important for alleviating poverty. More than half of Zambia’s population was living below the national poverty line in 2015. FMD is today considered to be endemic in Zambia, the most recent outbreak was in March 2018. No clinical cases of PPR have been found within the country so far but PPR is highly present in Zambia’s bordering countries in the north and Zambia is therefore under constant risk of the incursion of PPR. This study was carried out in the districts Nakonde and Mbala in northeastern Zambia on the border to Tanzania. The purpose was to investigate the seroprevalence of FMD and PPR in sheep and goats and to identify possible associations between animal characteristics, management of herds or trade and seropositivity. Serum samples were collected from 480 small ruminants from 160 herds in 40 randomly selected villages. Details on species, breed, origin, sex, age and history of disease were noted for each sampled individual. The owner of each herd was also questioned about management of the herd and trade. Serum samples were analyzed for presence of antibodies to foot-and-mouth-disease virus and peste-des-petits ruminants virus. Potential risk factors were analyzed with Fisher’s Exact Test to see if there were any significant correlations with seropositivity for FMD or PPR. The results showed that the dominating species in the villages was goat, and the dominating gender was female. The majority of the sampled animals were born at the farm where they were sampled, only two were bought from another country. The herd size varied between two and 34 animals. The majority of the farmers let their herds graze freely in the dry season and had them tethered during the rainy season. Seventy-one percent of the herds met other herds of sheep and/or goats on at least a weekly basis, and the proportion that met cattle as often was only 21%. Four percent of the herds met wild ruminants on at least a weekly basis. Most farmers never bought goats or sheep from other countries. The true herd seroprevalence in the Nakonde and Mbala districts was approximately 3.2 percent (95% CI 1.1; 7.4) for FMD and 0.03 percent (95% CI 0;3) for PPR. No risk factors for FMD or PPR seropositivity could be identified. The study design was considered to have good external and internal validity. The low seroprevalences of both FMD and PPR, relatively to what was expected, are most likely representative of the true seroprevalences in the target population. This study found serological evidence of PPR in a goat in Zambia, but this result needs to be confirmed with other methods since there is a high risk of the result being falsely positive. It could be interesting to do further research on whether there are any protective factors keeping the small ruminants from encountering FMDV and PPRV in this area since the seroprevalence was lower than expected for both diseases.