"Virus Topotypes and the Role of Wildlife in Foot and Mouth Disease in Africa"

Wilna Vosloo, A. D. S. Bastos, M. Sahle, O. Sangare and R. M. Dwarka

The epidemiology of foot and mouth disease (FMD) on the African continent is influenced by two different patterns, viz. a cycle where wildlife plays a role in maintaining and spreading the disease to other susceptible domestic animals and wild ungulates and another that is maintained within domestic animals. In southern Africa the former cycle predominates due to the presence of African buffalo (Syncerus caffer), the only wildlife species for which long term maintenance of FMD has been described. In East Africa both cycles probably occur, while in West Africa, due to the absence of sufficient numbers of wildlife hosts, the disease is maintained largely in the domestic cycle.

Foot and mouth disease is endemic to most countries in sub-Saharan Africa, except in southern Africa, where a number of countries have been able to control FMD by separating infected buffalo and other wildlife species from livestock using fences. Vaccination is used on a limited scale in domestic animals in close proximity of the potential infectious hosts. In other parts of the sub-continent control of FMD is surpassed by more urgent needs such as poverty and famine. However, FMD is one of the diseases that needs to be controlled should countries want to access international agricultural export markets. FMD cannot be eradicated from Africa unless all infected buffalo are removed, which from an ecological and ethical point of view would be untenable.

A better understanding of the epidemiology of the disease could aid in planning control strategies. The use of molecular epidemiological studies has assisted greatly in this regard by highlighting historical and current patterns of spread across borders and demonstrating the presence of viral topotypes that occur in both cycles of spread. Geographical clustering of virus strains into topotypes has been demonstrated for all 6 serotypes occurring on the continent and genetic variation is such that topotype distribution should be heeded when vaccination for control of FMD is considered.