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Journal
Publications
Dragon D.C., Elkin B.T., Nishi J.S., and
Ellsworth T.R. 1999 A review of anthrax in Canada and implications for
research on the disease in northern bison Journal of Applied
Microbiology 87, 208–213
PDF = 557 KB)
Abstract
During the first half of the century, the
majority of anthrax outbreaks in Canada occurred in the southern portions of
Ontario and Quebec and were often associated with pastures contaminated by
effluent
from textile industries dealing with imported animal materials. In 1952,
introduction of Federal regulations requiring disinfection of these
materials greatly reduced the incidence of anthrax in eastern Canada. Since
1962, domestic outbreaks of the disease have been reported almost
exclusively in cattle in the western prairie provinces. Between 1962 and
1993, nine anthrax epizootics have been recorded in the bison herds of the
Northwest Territories and northern Alberta resulting in the deaths of at
least 1309 animals. During the northern epizootics there has been a strong
sex bias in mortalities with the majority of carcasses being sexually mature
bulls. The northern epizootics occur during drought conditions in the late
summer, preceded by a wet spring, and end with the arrival of coolers
weather. It has been hypothesized that stress factors associated with these
meteorological conditions coupled with breeding stress during the late
summer rut may predispose the bulls to infection. Alternatively, the
meteorological conditions may work to concentrate anthrax spores in the
environment into low lying wallows preferentially utilized by the bulls.
Recent genetic analyses of Bacillus anthracis isolates from Canada and the
United States have identified that, while closely related to isolates from
domestic outbreaks, isolates from northern bison epizootics form their own
distinct strain. This suggests that the establishment of anthrax in northern
Canada was a singular event that occurred prior to the first recognized
epizootic in 1962. A review of the agricultural history of northern Canada
has identified several situations in the first half of the century which may
have provided the opportunity for the transfer of anthrax from cattle to the
indigenous bison. |
