Epidemiology of foot and mouth disease in Zambia.

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Sinkala, Yona
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The University of Zambia
Foot-and-mouth disease (FMD) is a highly infectious and devastating disease of livestock that has affected Zambia’s potential to boost the economy through trade in livestock commodities. The inadequate understanding, due to limited research based epidemiology data, of the disease dynamics has impacted negatively on its prevention and control. The aim of this study was to determine specific elements of FMD epidemiology that are important for understanding disease dynamics in Zambia. To conduct this study, firstly a retrospective analysis of FMD outbreaks between 1933 and 2012 was carried out in order to elucidate the temporal and spatial patterns that contributed to their occurrence. This was followed by a cross sectional study involving collection of sera and probang samples from cattle and buffalo including administration of a questionnaire at selected livestock/wildlife interface areas that was carried out to determine the seropositivity and associated risk factors. Included was molecular characterization of the circulating foot and mouth disease virus (FMDV) strains in these species. Furthermore, a transmission model incorporating carrier status was developed. Results of the study confirmed that FMD outbreaks remain confined to three high risk areas of Kafue Flats, lower Zambezi basin and northern Zambia. However, the patterns of occurrence of the disease varied in space and time (relative risk range 2.23 to 29.62) as well as in the causative serotypes and topotypes. Namwala district recorded the highest number of outbreaks with SAT 1 being the most predominant serotype in the district and across country (43.7 percent of the recorded outbreaks). And that agro-ecological zone, rainfall, distance away from buffalo migratory routes and international borders were significant factors of FMD occurrence. Furthermore, FMD animal seropositivity ranging from zero to 23 percent and transhumant husbandry practice as the main risk factor were identified. The study further isolated topotype II of SAT 2 from buffalo in Kafue National Park, a strain previously unknown to exist in Zambia. Furthermore, SAT 1 topotype I, closely related to the FMD outbreak virus of 2004/08, was isolated from vaccinated cattle in the livestock/wildlife interface of Monze and Lochnivar National Park. SAT 1 and SAT 2 were also isolated from buffalo in Lower Zambezi and Luambe National Parks. The FMD transmission model predicted an epidemic to peak by day 40 to 100 and die down by day 140 with an inter-epidemic period of nine to 23 years. The study provides significant elements of FMD epidemiology in Zambia including the spatial and temporal patterns, the subclinical infection and characterisation of circulating FMDV in cattle and buffalo at selected livestock/wildlife interface areas. Other elements included the carrier status in cattle, duration of epidemics and inter-epidemic periods. These elements may be considered in targeted risk surveillance, movement control, risk assessments and other disease prevention strategies at national and regional levels. Further work is recommended for better understanding of circulating FMDV in buffalo, carrier status in cattle within ecosystems and the role of livestock value chains in perpetuation of FMD outbreaks. Included is the optimization of the serological tests in use with antigens that are closely matched to the circulating field strains
Foot-and-mouth disease--Prevention. , Epidemiology--Foot and mouth disease. , Veterinary epidemiology.