American Bison - Buffalo Field Campaign

Alaska (Zarnke 1993) and from bison at Elk Island National
Park (EINP) in Alberta (Cool 1999; Gates et al. 2001b). In YNP,
positive antibody titres were detected in 31% of tested animals
(Taylor et al. 1997). There are unpublished data regarding sero-
reactivity from bison transported to Montana from WCNP in
South Dakota (K. Kunkel, personal communication). The Jackson
bison herd, with a known history of commingling with cattle,
has demonstrated low-level titres, but no evidence of BVD
antigen or clinical disease has been found (T. Roffe, personal
communication). Clinical BVD was reported in the EINP plains
bison herd in 1996, prompting a serological survey of plains
bison and wood bison herds (Cool 1999; Gates et al. 2001b).
Forty-seven percent of 561 plains bison from EINP tested sero-
positive for BVD; one tested positive for the virus antigen. At
least six plains bison deaths in EINP were attributed to the BVD
virus (Cool 1999). Tissues from the suspected cases of BVD
infected plains bison were submitted to the Animal Disease
Research Institute, Lethbridge, Alberta, Canada, and type 1
BVD virus was isolated (Tessaro and Deregt 1999). None of 352
wood bison in the Park tested sero-positive for BVD at the time.
Both plains and wood bison populations at EINP are vaccinated
for BVD during annual roundups. However, calves used in
translocations are not vaccinated to allow future screening of
recipient populations for BVD. In Poland, Sosnowski (1977)
reported BVD in a captive European bison. BVD is common in
cattle in North America and poses no known risk to humans.
5.1.8 Johne’s disease
Johne’s disease (JD) is caused by the etiologic agent
Mycobacterium avium subsp. paratuberculosis, a hardy
bacterium related to the agents of leprosy and tuberculosis.
It occurs worldwide affecting a variety of domestic and wild
ruminants including bison, cattle, and sheep (Buergelt et
al. 2000; Williams 2001). Infections often lead to chronic
granulomatous enteritis with clinical signs of diarrhoea, weight
loss, decreased milk production, and mortality. JD is common
in cattle. Recent studies have shown that more than 20% of
dairy herds in the U.S. have JD (Chi et al. 2002; Ott et al. 1999)
causing an estimated economic loss of more than US$200
million annually. JD typically enters a herd when infected,
asymptomatic animals are introduced. Unpasteurised raw
milk or colostrum may be a source of infection for artificially
raised calves. Animals are most susceptible to infection during
their first year of life. Neonates most often become infected
by swallowing small amounts of contaminated manure from
the ground or from their mother’s udder. Animals exposed to a
very small dose of bacteria at a young age, and older animals,
are not likely to develop clinical disease until they are much
older. After several years, infected animals may become patent
and shed mycobacteria in their faeces. Typically, pre-patent
animals do not show symptoms of disease; consequently, most
32 American Bison: Status Survey and Conservation Guidelines 2010
infections go unnoticed and undiagnosed. There is no treatment
for animals infected with JD and prevention is the best control
measure. Humans are not considered susceptible, but M. a.
paratuberculosis has been isolated in patients with chronic
enteritis (Crohn’s disease) (Chiodini 1989). JD is not considered
to be a disease problem when bison are on open rangelands
and managed at low density. However, restrictions may apply
to inter-jurisdictional movement of animals from known infected
herds. Hence, maintaining low risk status for bison herds
used as a source for conservation projects is an important
consideration.
In 1998, the U.S. Animal Health Association approved the
Voluntary Johne’s Disease Herd Status Program for cattle
(VJDHSP). The VJDHSP provides testing guidelines for States
to use to identify livestock herds as low risk for JD infection.
With numerous tests over several years, herds progress to
higher status levels. The higher the status level, the more
likely it is that a herd is not infected with JD. In April 2002,
USDA-APHIS-Veterinary Service incorporated portions of
this programme into national programme standards: Uniform
Program Standards for the Voluntary Bovine Johne’s Disease
Control Program (VBJDCP). VBJDCP-test-negative herds serve
as a source of low JD risk stock. Testing for JD in conservation
herds has been sporadic and opportunistic. Diagnostic tools
are being developed and improved. There are no reports of JD
in conservation bison herds in the literature, however, some
commercial operations have discovered JD, and in many cases
are managing to prevent its spread and reduce its impact on
the industry.
5.1.9 Malignant catarrhal fever (sheep associated)
Malignant catarrhal fever (MCF) is a serious, often fatal disease
affecting many species of the Order Artiodactyla. It is caused
by viruses of the genus Rhadinovirus. At least 10 MCF viruses
have been recognised worldwide and five viruses have been
linked to disease. The viruses most significant to livestock are
those carried by sheep, goats or wildebeest (Connochaetes
spp.). Although ovine herpes virus type 2 (sheep associated
MCF) does not cause disease in its natural host, domestic
sheep, it does cause MCF in bison. Serological testing indicated
that it is common in domestic goats (61%) and sheep (53%)
in the U.S. (Li et al. 1996). MCF is an important disease in the
commercial bison industry as it is one of the most infectious
diseases of bison, especially at high densities (Heuschele and
Reid 2001). It causes highly lethal infections in bison, with
the reported incidence of mortality in a herd of up to 100%
(Schultheiss et al. 2001). Infections proceed rapidly to clinical
disease. MCF is expressed in two forms, acute and chronic,
but regardless, death ensues in most cases. In the acute form,
bison usually die within 7–10 days of infection or within 48 hr
of becoming symptomatic. Alternatively, death may ensue as