This report describes the molecular characterization of a serotype O foot‐and‐mouth disease virus (FMDV) recovered from a field outbreak in the Zambezi region, Namibia during July 2021. Sequence analysis demonstrates that this FMDV belongs to the O/EA‐2 topotype sharing closest nucleotide identity (99.5%) to FMD viruses collected since 2018 in Zambia. This is the first detection of serotype O in Namibia, and together with the cases that have been recently detected in southern Zambia, represent the first time that this serotype has been detected in the Southern African FMD endemic pool since 2000, when a virus of Asian origin (O/ME‐SA/PanAsia) caused an outbreak in South Africa. This incursion poses a new threat for the region and the potential onward spread of O/EA‐2 will now need to be closely monitored since serotype O vaccines are not widely used in Namibia, nor in neighbouring countries.
A study was conducted to determine the serotypes of foot-and-mouth disease viruses (FMDV) circulating in African buffaloes (Syncerus caffer) from selected areas in Zambia. Sera and probang samples were collected between 2011 and 2012 and analysed for presence of antibodies against FMDV while probang samples were used to isolate the FMDV by observing cytopathic effect (CPE). Samples with CPE were further analysed using antigen ELISA. High FMD seroprevalence was observed and antibodies to all the three Southern African Territories (SAT) serotypes were detected in four study areas represented as follows: SAT2 was 72.7 percent; SAT1 was 62.6 percent; and SAT3 was 26.2 percent. Mixed infections accounted for 68.6 percent of those that were tested positive. For probang samples, CPE were observed in three of the samples, while the antigen ELISA results showed positivity and for SAT1 (n = 1) and SAT2 (n = 2). It is concluded that FMDV is highly prevalent in Zambian buffaloes which could play an important role in the epidemiology of the disease. Therefore livestock reared at interface with the game parks should be included in all routine FMDV vaccination programmes.
Foot-and-mouth disease (FMD) virus (FMDv), like other ribonucleic acid (RNA) genome viruses, has a tendency to mutate rapidly. As such, available vaccines may not confer enough cross-protection against incursion of new lineages and sublineages. This paper is a retrospective study to determine the topotypes/lineages that caused previous FMD outbreaks in 6 southern African countries and the efficacy of the current vaccines to protect cattle against them. A total of 453 bovine epithelial tissue samples from 33 FMD outbreaks that occurred in these countries from 2014 to 2018 were investigated for the presence of FMDv. The genetic diversity of the identified Southern African Type (SAT)-FMD viruses was determined by comparing sequences from outbreaks and historical prototype sequences. Of the 453 samples investigated, 176 were positive for four FMDv serotypes. Out of the 176 FMD positive cases there were 105 SAT2 samples, 32 SAT1 samples, 21 SAT3 samples, and 18 serotype O samples. Phylogenetic analysis grouped the SATs VP1 gene sequences into previously observed topotypes in southern Africa. SAT1 viruses were from topotypes I and III, SAT2 viruses belonged to topotypes I, II, III, and IV, and SAT3 viruses were of topotypes I and II. Vaccine matching studies on the field FMDv isolates produced r1-values greater than or equal to 0.3 for the three SAT serotypes. This suggests that there is no significant antigenic difference between current SAT FMD vaccine strains and the circulating SAT serotypes. Therefore, the vaccines are still fit-purpose for the control FMD in the region. The study did not identify incursion of any new lineages/topotypes of FMD into the sampled southern African countries.
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