Challenges and prospects for the control of foot-and-mouth disease: an African perspective

Abstract

Abstract:The epidemiology of foot-and-mouth disease (FMD) in Africa is unique in the sense that six of the seven serotypes of FMD viruses (Southern African Territories [SAT] 1, SAT2, SAT3, A, O, and C), with the exception of Asia-1, have occurred in the last decade. Due to underreporting of FMD, the current strains circulating throughout sub-Saharan Africa are in many cases unknown. For SAT1, SAT2, and serotype A viruses, the genetic diversity is reflected in antigenic variation, and indications are that vaccine strains may be needed for each topotype. This has serious implications for control using vaccines and for choice of strains to include in regional antigen banks. The epidemiology is further complicated by the fact that SAT1, SAT2, and SAT3 viruses are maintained and spread by wildlife, persistently infecting African buffalo in particular. Although the precise mechanism of transmission of FMD from buffalo to cattle is not well understood, it is facilitated by direct contact between these two species.Once cattle are infected they may maintain SAT infections without the further involvement of buffalo. No single strategy for control of FMD in Africa is applicable. Decision on the most effective regional control strategy should focus on an ecosystem approach, identification of primary endemic areas, animal husbandry practices, climate, and animal movement. Within each ecosystem, human behavior could be integrated in disease control planning. Different regions in sub-Saharan Africa are at different developmental stages and are thus facing unique challenges and priorities in terms of veterinary disease control. Many science-based options targeting improved vaccinology, diagnostics, and other control measures have been described. This review therefore aims to emphasize, on one hand, the progress that has been achieved in the development of new technologies, including research towards improved tailored vaccines, appropriate vaccine strain selection, vaccine potency, and diagnostics, and how it relates to the conditions in Africa. On the other hand, we focus on the unique epidemiological, ecological, livestock farming and marketing, socioeconomic, and governance issues that constrain effective FMD control. Any such new technologies should have the availability of safe livestock products for trade as the ultimate goal.

Seroprevalence of some Infectious transboundry diseases in cattle imported from Sudan to Egypt

“…This can be explained by that among every 20,000 head of imported cattle from Sudan, at confidence levels between 5% and 90% there is a probability of introducing 75 infected animal with a new strain of FMDV or 3.75 infected animal among 1,000 imported animal [40]. This may be the reason that many outbreaks of FMD have been occurred, with the virus remain circulated in vaccinated cattle populations in Egypt as a result of continuous introduction genetically and immunological different serotypes and topotypes [53], for example, most of the current FMD SAT-2 outbreaks reported in Egypt are associated with animals coming from Sudan and Ethiopia [54].…”

Co-Circulation of Multiple Serotypes of Bluetongue Virus in Zambia

“…Most small-and large-scale farmers in Zambia have exploited the available regional markets for small ruminants. Furthermore, the transfrontier increase in movement of livestock that is driven by price differences, socio-cultural links, climate change, transhumance and nomadism [39], necessitates the need for regional BT prevention and control strategies that will mitigate potential socio-economic effects.…”

Diagnostic and Epitope Mapping Potential of Single-Chain Antibody Fragments Against Foot-and-Mouth Disease Virus Serotypes A, SAT1, and SAT3

“…Both the solid-phase competition (SPCE) and LPBE ELISAs for SAT1, SAT2, and SAT3 are OIE recognized and well established assays. Considering the high genetic diversity of the SAT-type viruses (2,6,26,49), there is a continuous need for improvement of these assays as crossreactivity has been noted with the SAT types using this assay. Additionally, for FMD vaccine matching where the antigenic variability of field virus strains is measured against current vaccine strains, the virus neutralization assay is utilized.…”

“…Neutralizing antigenic sites have been identified for serotype A (15)(16)(17), O (18)(19)(20)(21), C (22), Asia-1 (23), and SAT2 (19,24,25). However, information regarding the antigenic determinants of SAT serotypes, which are confined geographically to Africa, is scarce (26). Mapped SAT2 epitopes include: (i) βG-βH loop of VP1; (ii) residue 210 in the C-terminus of VP1; (iii) VP1 84-86, 109-111, VP2 71,72,133,134; and (iv) VP1 159, VP2 71-72, 133-134, 148-150 (19,24,25,27,28).…”

“…To date, no neutralizing sites have been determined for viruses of the SAT3 serotype. It has been shown that the majority of FMDV-neutralizing antibodies are directed against conformational epitopes located on the β-barrel connecting loops, especially the highly mobile βG-βH loop in VP1 (15,18,26,29,30). Therefore, knowledge of the amino acid residues that comprise the antigenic determinants of FMDV, and those that function as protective epitopes in particular, will greatly improve our understanding of virus neutralization in vivo (12,26,31).…”