Abstract
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.
Highlights
Foot-and-mouth disease (FMD) is a contagious viral disease clinically characterized by lesions in the mouth and feet of cloven-hoofed animals; the disease affects more than 70 animal species [1,2,3,4]
FMD outbreaks are sporadically reported in most countries of the southern Africa region [27, 43, 44] and in the past decade (2004–2013), they have occurred in various countries of southern Africa [26]. e underreporting of FMD in the region contributes to sampling bias; only those serotypes that occur where reporting is done will seem prominent in the region. is paper is a retrospective review of FMD outbreaks to determine topotype/lineage that caused footand-mouth disease outbreaks in some southern African countries during the period between 2014 and 2018
A single outbreak was confirmed in a country hitherto free from FMD. is outbreak in cattle occurred in August 2016 in the Island of Mauritius; the disease outbreak was confirmed to be caused by FMD virus (FMDv) serotype O which belonged to the Middle East South Asia (ME-SA) topotype; the disease was effectively controlled by vaccination [45]. e disease incursion into this country demonstrates that no country is safe from FMDv and the need for high surveillance and emergency preparedness, such as maintenance of strategic FMD vaccine banks, cannot be overemphasised [46]
Summary
Foot-and-mouth disease (FMD) is a contagious viral disease clinically characterized by lesions in the mouth and feet of cloven-hoofed animals; the disease affects more than 70 animal species [1,2,3,4]. In Africa, direct economic losses associated with reduction of livestock products (meat and milk) due to FMD infection are estimated at US$2.3 billion per year [11, 12]. All FMD virus (FMDv) serotypes except Asia 1 and C serotypes are endemic in Africa; serotype C was last isolated worldwide in 2004 [20]. Among the five FMDv serotypes that occur in Africa, the three SATs are unique to Africa [21, 22]; there have been reports of its incursion outside the continent in the past [23, 24]. In southern Africa, the SAT serotypes have been closely linked to the African buffalo (Syncerus caffer) which is attributable to the continued presence of these FMDv serotypes in the region [20, 22, 25,26,27]
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