Tubercle and Lung Disease (2000) 80(4/5), 229I236 ^ 2000 Harcourt Publishers Ltd doi: 10.1054/tuld.2000.0250, available online at http://www.idealibrary.com.on The development of wildlife control strategies for eradication of tuberculosis in cattle in Ireland E. Gormley, J.D. Collins Department of Large Animal Clinical Studies, Faculty of Veterinary Medicine, University College Dublin, Dublin, Ireland Summary Wildlife species, such as badgers, act as maintenance hosts for Mycobacterium bovis and contribute to the spread and persistence of tuberculosis in associated cattle populations. In areas in which there is a tuberculosis problem affecting a number of herds, the involvement of infected wildlife in the introduction of M. bovis infection into herds act as a constraint to eradication of the disease. Epidemiological evidence demonstrates a high prevalence of tuberculosis in badgers, and controlled studies involving comprehensive badger removal have shown that this strategy can serve to significantly reduce cattle reactor rates in the targeted areas. However, as the badger is a protected wildlife species, alternative strategies are required to combat the disease. Targeted vaccination of wildlife species against tuberculosis is an option which, if successfully employed, could directly facilitate the advancement of bovine tuberculosis eradication in affected areas. Any proposed vaccination programme would need to be undertaken against the background of an exhaustive investigation of the cattle and herd management-related factors, and take account of environmental issues. ^ 2000 Harcourt Publishers Ltd INTRODUCTION The principal maintenance host for Mycobacterium bovis is the infected bovine animal. In Ireland, as in other de- veloped countries today, tuberculosis rarely affects cattle to the extent of causing clinical signs, as was the case in the 1950s when the Bovine Tuberculosis Eradication Scheme was 9rst introduced. Rather, the majority of affec- ted cattle now disclosed by the national programme of bovine tuberculosis eradication are found to be in the early stages of the disease and, at post-mortem examina- tion, most cases show only local involvement of the regional lymph nodes of the head and thorax. The identi9cation and early disposal of such animals form the basis of national bovine tuberculosis eradication programmes worldwide. Success is dependant upon the removal of the infected animal before it becomes a source of infection of M. bovis for other animals and of contami- nation of their environment. Meanwhile, the cases of advanced tuberculosis which are encountered serve to Correspondence to: Eamonn Gormley, Department of Large Animal Clinical Studies, Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland. Tel.: #353 1 668 7988 ext. 2552; Fax: #353 1 667 1460; E-mail: egormley@ucd.ie remind one of the progressive nature of this disease and of the extent to which animals so affected may infect other cattle and contaminate their own environment if they go undetected. On the other hand, the rarity of such cases shows that, provided prompt corrective action is taken at herd level, the problem of tuberculosis in cattle, with few exceptions, is amenable to control. Reliance upon the results of the tuberculin test, or on other immunological tests, without consideration of the epidemiological data resulting from 9eld investigations, can lead to a false sense of security in local situations where non-bovine sources of M. bovis co-exist with the cattle population. The tuberculin test, in its various forms, has performed well as a mass screening test in cattle, but can provide only retrospective evidence of ex- posure to infection. However, the occurrence of another animal host of M. bovis on the farm, not included in the surveillance testing and control programme, which is ca- pable of transmitting infection to the herd, represents a threat to the otherwise unexposed herd which cannot be countered by the use of the tuberculin test alone. In addressing the problems posed by wildlife species, it is 9rst necessary to discount as far as possible all other factors, including husbandry practices which favour the transmission of M. bovis between cattle, before embarking 229