Abstract
The only vaccine ever approved for human tuberculosis was developed a century ago from an isolate of Mycobacterium bovis derived from a tuberculous cow. Initial safety and efficacy studies of an attenuated version of this isolate were conducted in cattle and other animals. In 1921 the first human, an infant, was orally dosed with this attenuated strain that came to be known as M. bovis bacillus Calmette-Guérin (BCG); named for Albert Calmette and Camille Guérin, the two French scientists that developed the strain. Since 1921, billions of people have been vaccinated with BCG making it the oldest, most widely used, and safest vaccine in use today. It is also the tuberculosis vaccine most studied for use in wildlife, including deer. While BCG vaccination of deer may not reliably prevent infection, it consistently decreases lesion severity, minimizing large, necrotic lesions, which often contain large numbers of bacilli. It is believed that decreased lesion severity correlates with decreased disease transmission; however, this hypothesis remains to be proven. Safety studies in white-tailed deer show BCG may persist in lymphoid tissues for up to 12 months; a factor to be considered in deer used for food. Beyond efficacy and safety, methods of vaccine delivery to free-ranging deer are also under investigation, both in the laboratory and in the field. The ideal delivery method is effective, efficient and safe for non-target species, including livestock. Ingestion of BCG by cattle is of special concern as such cattle may present as “false positives” using currently approved diagnostic methods, thus interfering with efforts by animal health agencies to monitor cattle for tuberculosis. An effective BCG vaccine for deer would be of value in regions where free-ranging deer represent a potential source of M. bovis for livestock. Such a vaccine would also be beneficial to farmed deer where M. bovis represents a serious threat to trade and productivity.
Highlights
Mycobacterium bovis is the cause of tuberculosis in most animal species, including man
In northeast Michigan, USA there is a focus of M. bovis infection in free-ranging white-tailed deer (Odocoileus virginianus) where infected deer have been implicated as the source of infection in 69 cattle herds from 1995 through 2017
The most studied tuberculosis vaccine in deer, as well as other wildlife is the attenuated strain of M. bovis known as bacillus Calmette-Guérin (BCG), named for Albert Calmette and Camille Guérin, two French scientists at the Pasteur Institute that developed the strain [26]
Summary
Mycobacterium bovis is the cause of tuberculosis in most animal species, including man. In addition to white-tailed deer in the US, there is general consensus that the European badger (Meles meles) in the United Kingdom and the Republic of Ireland, the brushtail possum (Trichosurus vulpecula) in New Zealand, and the European wild boar (Sus scrofa) in the Iberian Peninsula represent wildlife reservoirs of M. bovis and can be a persistent source of re-infection of cattle [5,6,7,8,9,10,11,12]. Vaccination of wildlife to reduce wildlife-to-cattle transmission has been investigated, with some vaccines progressing to field trials [13, 14]. There have been no widespread efforts to vaccinate wildlife to control tuberculosis, there is currently one approved vaccine for use in European badgers [25] and field trials are progressing [14]
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