Foot and mouth disease in wildlife

Abstract

Occasionally foot and mouth disease (FMD) can be destructive of wildlife, as apparently occurred in South Africa in the late 19th century where large numbers of impala Aepyceros melampus succumbed, and more recently in Israel where high mortality occurred in mountain gazelles Gazella gazella (Macaulay, 1963; Shimshony, 1988). More usually, as is often the situation with domestic livestock in extensive production systems, infection of wildlife with FMD results in a relatively mild disease from which affected animals recover in a week or two. The significance of the disease for wildlife lies largely in the potential that clovenhoofed wild animals have for transmitting the disease to domestic livestock where, especially in intensive farming situations, the disease may be severely debilitating and result in serious economic losses for farmers. Perhaps more significant is the effect the presence of the disease (more precisely, the infection) has on international trade in livestock and livestock products. Therefore, the indirect effects of the infection often far outweigh the direct effects that it has on animals themselves, be they wild or domestic. Some wild ruminants also have the potential to become carriers of the infection i.e. the virus may persist in the absence of any obvious sign of disease. These animals, albeit extremely rarely, transmit the infection to cohorts of the same or other species with which they are in close contact. Until the end of the 19th century FMD was widespread throughout the world, but from the early 20th century the disease was progressively eradicated from the developed world because of its severe economic impact on intensive livestock production. Presently, North America, most of Europe, Australia and New Zealand among the major livestock rearing areas of the world are free of FMD. It persists currently in South America, most African countries, the Middle East, and many parts of south, central and south-east Asia. Major re-incursions of the disease have occurred recently in south-east Asia (Taiwan, Japan, South Korea and Indonesia), South America (Argentina, Uruguay and Brazil) and western Europe (UK, The Netherlands, France and Ireland). In some cases this has involved the transcontinental spread of the so-called pan-Asian topotype O virus from Asia. This occurred in September 2000 in South Africa (Sangare et al., 2001) and in February 2001 in the UK (Samuel and Knowles, 2001). Wildlife, however, has not been responsible for any of these re-incursions and, as far as is known, none became infected by either direct or indirect contact with domestic livestock during these incidents. On the other hand, fear of spread of the infection into collections of rare and valuable species, including zoological collections, has resulted in much conjecture as to how to protect these animals in the event of an epizootic. Furthermore, what the consequences would be in the event that measures taken to prevent infection prove ineffective is currently a subject of considerable debate. There has been a strong lobby to vaccinate such animals to protect them from infection but how effective that would be is a matter of opinion. Such action could interfere with the trading status of the country concerned. For countries that are members of the Office International des Epizooties (OIE), the international animal health organisation that sets international trading norms with respect to animals and animal products, to achieve the most favourable trading status (freedom from FMD without vaccination), no animals vaccinated against FMD within the last 12 months should be present on the territory of the country concerned. No distinction is made between wildlife and domestic live* Corresponding author. E-mail address: gavin.thomson@oau-ibar.org (G.R. Thomson). Virus Research 91 (2003) 145 /161