Infectious diseases of animals in sub-Saharan Africa: The wildlife⁄livestock interface

Infectious diseases of animals in sub-Saharan Africa: The wildlife/livestock interface

R G BENGIS, R A KOCK, G R THOMSON AND R D BIGALKE

Introduction

The critical need for rural development to support the rapidly growing human population in sub-Saharan Africa is increasing the pressure on wildlife in the region. Poverty and lack of food security are root causes of the massive destruction of habitats and animal populations.25, 58, 59, 96 Wilderness areas are being encroached upon and are often perceived by rural communities as legitimate sources of natural resources from which they are unreasonably precluded access for livestock grazing, collection of firewood, thatching grass and other products, and subsistence hunting. On the other hand, the potential of the rich wildlife heritage of the region for sustainable exploitation and therefore economic development is obvious. It is also important for sub-Saharan Africa to preserve the diversity of its fauna and flora, because nowhere else on Earth is there a comparable resource. It is difficult to reconcile these essentially conflicting imperatives.

The growth in the livestock population of Africa is no longer keeping pace with human population increase, and livestock productivity is not improving in most regions to compensate for the increasing needs.96 There are a number of reasons for this static livestock economy, the most important being land degradation,103 declining livestock production and faltering disease control services.96 There is also a decline in wildlife populations, even within many protected areas, with over 60 per cent of all such areas now being relatively depleted of antelopeandlarge bovids.48 This resource willnolonger provide the supplementary (and free) food enjoyed by past generations. The concomitant increasing need for landontheonehand,and greater awareness of the intrinsic and economic value of wildlife resources and savannah biodiversity on the other, result in the issues at the interface between livestock and wildlife becoming increasingly acute and politicized.

The presence of diseases that occur in both domestic and wild animals and which may be transmitted from one to the other constitutes one of the constraints on land-use options in sub-Saharan Africa. Although the interface results in some disease transmission and economic loss, it should be appreciated that with the massive decline in available habitats for wild herbivores in most regions of Africa, the extent of this interface is actually shrinking on the macro-scale, yet intensifying in other regions. In addition, amongst the wide variety of wild artiodactylids in Africa, only a few species are epidemiologically important with regards to serious economic livestock diseases. These are African buffalo (Syncerus caffer), warthog (Phacochoerus africanus), bushpig (Potamochoerus, sp.) greater kudu (Tragelaphus strepsiceros), bushbuck (Tragelaphus scriptus), and wildebeest (Connochaetes spp.), which have all been linked to one or more of the following important diseases: rinderpest (RP), foot-and-mouth disease (FMD), African swine fever (ASF), malignant catarrhal fever (MCF), East Coast fever (ECF), bovine petechial fever, and trypanosomosis. These major infectious diseases of livestock and wildlife are comprehensively presented elsewhere in this book.

With this background, the objective of this chapter is to discuss the key wildlife-related issues that impact on disease persistence and control. These include free-ranging wildlife as disease reservoirs, alien diseases introduced with domestic animals, pastoralism and transhumance, the use of fencing, and compliance with animal health requirements, which are necessary to gain access to international markets and trade. In addition, certain current trends in wildlife management, such as the development of game conservancies and transfrontier parks, and the increasingly popular introduction and relocation of wildlife to privately owned game reserves, which may expand or intensify the interface, are also of concern and are discussed.

Historical perspective

Sub-Saharan Africa has a larger number and diversity of indigenous free-ranging wild mammals than any other comparable land mass. This is especially true for ruminants. As a possible consequence, an equally impressive array of pathogenic micro-organisms and macro-parasites, as well as arthropod vectors of certain micro-organisms, have coevolved with their hosts for millennia, which has culminated in evolutionary adaptation and tolerance between host and pathogen or parasite, and the development of endemic stability. Infection is usually ‘silent’ in the definitive wildlife hosts, which serve as reservoirs of specific pathogens. Infection of wildlife species other than the definitive hosts may result in disease, which is generally mild. Infection rates may be high, but clinical expression of disease is generally cryptic in these ‘incidental hosts’.

The evolution of the wildlife/livestock interface in sub-Saharan Africa is inseparably linked with the more recent history of Homo sapiens on this continent. The best examples of the recent history of human migration and interaction with livestock are those which took place in southern Africa; some of these are used here to illustrate certain major factors that have played or continue to play a role at this interface.

The San (Bushmen) were the first modern humans to occupy southern Africa. They were...

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