Epidemiological Dynamics of Foot-and-Mouth Disease in the Horn of Africa: The Role of Virus Diversity and Animal Movement

Abstract

The Horn of Africa is a large area of arid and semi-arid land, holding about 10% of the global and 40% of the entire African livestock population. The region’s livestock production system is mainly extensive and pastoralist. It faces countless problems, such as a shortage of pastures and watering points, poor access to veterinary services, and multiple endemic diseases like foot-and-mouth disease (FMD). Foot-and-mouth disease is one of the most economically important livestock diseases worldwide and is endemic in most developing countries. Within Africa, five of the seven serotypes of the FMD virus (FMDV) are described, but serotype C is not circulating anymore, a burden unseen anywhere in the world. The enormous genetic diversity of FMDV is favored by an error-prone RNA-dependent RNA polymerase, intra-typic and inter-typic recombination, as well as the quasi-species nature of the virus. This paper describes the epidemiological dynamics of foot-and-mouth disease in the Horn of Africa with regard to the serotypes and topotypes distribution of FMDV, the livestock production systems practiced, animal movement, the role of wildlife, and the epidemiological complexity of FMD. Within this review, outbreak investigation data and serological studies confirm the endemicity of the disease in the Horn of Africa. Multiple topotypes of FMDV are described in the literature as circulating in the region, with further evolution of virus diversity predicted. A large susceptible livestock population and the presence of wild ungulates are described as complicating the epidemiology of the disease. Further, the husbandry practices and legal and illegal trading of livestock and their products, coupled with poor biosecurity practices, are also reported to impact the spread of FMDV within and between countries in the region. The porosity of borders for pastoralist herders fuels the unregulated transboundary livestock trade. There are no systematic control strategies in the region except for sporadic vaccination with locally produced vaccines, while literature indicates that effective control measures should also consider virus diversity, livestock movements/biosecurity, transboundary trade, and the reduction of contact with wild, susceptible ungulates.

Foot and mouth disease vaccine efficacy in Africa: a systematic review and meta-analysis

“…The introduction of FMD into FMD-free regions, such as North Africa and Europe, underscores the need for strong intervention strategies ( 65 ). Key challenges include the diversity of the FMD virus, inadequate monitoring systems, varied animal species and farming practices, and technical issues like maintaining the cold chain ( 66 ). Even with effective vaccines, outbreaks in vaccinated populations suggest problems such as insufficient coverage, strain mismatches, and waning immunity ( 52 ).…”

“…Even with effective vaccines, outbreaks in vaccinated populations suggest problems such as insufficient coverage, strain mismatches, and waning immunity ( 52 ). As highlighted in studies by Katie Lloyd-Jones, Woldemariyam ( 52 , 66 ), and Ayelet ( 67 ), these issues, along with uncontrolled animal movement and weak biosecurity, complicate FMD control. Hence, regular updates and adaptations to vaccination strategies are vital, considering the dynamic nature of FMDV serotypes.…”

The Immunogenicity of a Foot-and-Mouth Disease Virus Serotype O Vaccine in Commercial and Subsistence Cattle Herds in Zambia

“…The causative agent, FMD virus (FMDV), is contagious and antigenically diverse, with six currently circulating serotypes that do not cross-protect. This role of virus diversity in the epidemiological dynamics of FMD in Africa has been described [ 1 ].…”