A Five-Year Retrospective Study of Foot-and-Mouth Disease Outbreaks in Southern Africa, 2014 to 2018

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.

Outbreaks of Foot-and-Mouth Disease in Burundi, East Africa, in 2016, Caused by Different Serotypes

“…About half (35 out of 69) of these positive samples were submitted to virus isolation. FMDV was isolated from about half (18 out of 35) of them, a success rate similar to previously reported [ 50 ]. On the one hand, this illustrates the importance of early reporting and early sampling of cases of FMD to obtain samples with a high viral load [ 29 ], but it also illustrates the challenge of sampling and transportation under tropical conditions and the negative effects of subsequent freezing, long-distance air transportation, and thawing on the success rate of isolating FMDV [ 51 ].…”

Epidemiological Patterns of Foot and Mouth Disease in Egypt and Other African Countries

“…Regional veterinary services from all over the world produced reports that served as the basis for this data collection. The Progressive Control Pathway (PCP) for FMD (FAO et al, 2018), a global progressive control method for FMD led by the FAO, is one example of an evidence-basedFMDV circulation management method that heavily relies on outbreak information. Large-scale outbreak data are crucial for understanding the epidemiological situation, developing treatments, and evaluating the effectiveness of FMDV control approaches.…”

“…These vaccines are offered in two purification levels: semi purified and highly purified. The latter level, known as DIVA or marker vaccines, enables the distinction between infection-and vaccine-induced antibodies (Fana et al, 2021).…”

“…In order to manage FMD, Namibia and Mozambique now use utilize a trivalent vaccine (SAT1-3) rather than a bivalent vaccine (SAT 1-2). Zambia now has a heavier burden of FMD management through vaccination, and it's possible that they won't be able to stop Pool 4's exotic virus outbreak from spreading to Zimbabwe, Botswana, and Namibia.In order to effectively control and prevent FMD caused by exotic viruses moving into the region from eastern Africa, it is recommended that coordinated measures led by SADC and supported by international donor organizations like the World Bank, FAO, and/or EU be begun as soon as possible (Fana et al, 2021).…”

“…These vaccines may persuade more African nations to implement regular preventive immunizationprograms to curb and prevent the spread of FMD. In addition to facilitating regional and global trade of animals, these routine immunization campaigns will stop disease outbreaks in susceptible animals, eradicating poverty and ensuring prosperity and food security (Fana et al, 2021). Aidaros, H. A.…”