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About the Authors:
Mitchell V. Palmer
* E-mail: [email protected]
Affiliation: National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa, United States of America
Tyler C. Thacker
Affiliation: National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa, United States of America
W. Ray Waters
Affiliation: National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa, United States of America
Suelee Robbe-Austerman
Affiliation: National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, Iowa, United States of America
Introduction
Mycobacterium bovis is the cause of tuberculosis in animals and has a broad host range that includes cattle, deer and humans. Human infection can result in disease indistinguishable from that caused by M. tuberculosis. During the early to mid 20th century, public health concerns posed by zoonotic transmission of M. bovis from cattle to humans prompted many countries to implement national programs to eradicate tuberculosis from cattle [1]. In most developed nations eradication campaigns have been successful in decreasing the prevalence of bovine tuberculosis. Nevertheless, in spite of long-standing and costly efforts, some countries have found it impossible to eradicate tuberculosis from the cattle population. One obstacle responsible for many faltering eradication campaigns is the presence of a wildlife reservoir of M. bovis infection [2]. In most cases, wildlife became infected when M. bovis “spilled over” from cattle decades ago during periods of high disease prevalence in cattle; however, in many regions, M. bovis is now “spilling back” from wildlife to cattle, impeding the progress of eradication [3], [4]. Although some wildlife species are dead-end hosts, inconsequential in maintenance of the disease within a region and transmission to cattle (i.e. spillover hosts), other species are capable of maintaining disease and transmitting M. bovis to other susceptible hosts (i.e. maintenance hosts). Recognized wildlife maintenance hosts of M. bovis include the brushtail possum (Trichosurus vulpecula) in New Zealand, European badger (Meles meles) in the United Kingdom and Republic of Ireland, wild boar (Sus scrofa) in Spain, African buffalo (Syncerus caffer) in South Africa and white-tailed deer (Odocoileus virginianus) in the United States (USA). Control of disease in wildlife...