American Bison - Buffalo Field Campaign

cattle at similar levels to S19 (Cheville et al. 1993). Doses of
RB51 considered to be safe in cattle were found to induce
endometritis, placentitis, and abortion in adult bison (Palmer
et al. 1996). However, Roffe et al. (1999a) found RB51 had no
significant adverse effects on bison calves. The safety and
efficacy of RB51 in bison remains unclear but, nonetheless,
it was provisionally approved for use in bison in the U.S. The
vaccine is not recognised in Canada and vaccinated cattle are
not allowed into the country (CFIA 2007). Every bison imported
into Canada from the U.S. must be quarantined from the time of
its importation into Canada until it proves negative to tests for
brucellosis performed not less than 60 days after it was imported
into Canada (CFIA 2007).
Quarantine protocols have been developed for bison to
progressively eliminate all animals exposed to brucellosis from
a population (APHIS, USDA 2003; Nishi et al. 2002b). These
protocols have been successful for eliminating brucellosis in
wood bison through the Hook Lake project and are currently
being attempted in the GYA (Aune and Linfield 2005; Nishi et al.
2002b). Results from these two studies, and other case studies
(HMSP, WCNP and EINP), have shown that brucellosis can be
effectively eliminated from exposed populations with a high
degree of certainty using test and slaughter protocols.
5.1.6 Bovine tuberculosis
Bovine tuberculosis (BTB) is a chronic infectious disease caused
by the bacterium Mycobacterium bovis (Tessaro et al. 1990).
The primary hosts for BTB are cattle and other bovid species,
such as bison, water buffalo (Bubalus bubalis), African buffalo
(Syncerus caffer), and yak (Bos grunniens). Primary hosts are
those species that are susceptible to infection and will maintain
and propagate a disease indefinitely under natural conditions
(Tessaro 1992). Other animals may contract a disease, but
not perpetuate it under natural conditions; these species are
secondary hosts. The bison is the only native species of wildlife
in North America that can act as a true primary host for M. bovis
(Tessaro 1992). Historical evidence indicates that BTB did not
occur in bison prior to contact with infected domestic cattle
(Tessaro 1992). Currently, the disease is only endemic in bison
populations in and near WBNP, where it was introduced with
translocated plains bison during the 1920s. BTB is primarily
transmitted by inhalation and ingestion (Tessaro et al. 1990);
the bacterium may also pass from mother to offspring via the
placental connection, or through contaminated milk (FEARO
1990; Tessaro 1992). The disease can affect the respiratory,
digestive, urinary, nervous, skeletal, and reproductive systems
(FEARO 1990; Tessaro et al. 1990). Once in the blood or lymph
systems the bacterium may spread to any part of the host and
establish chronic granulomatous lesions, which may become
caseous, calcified, or necrotic (Radostits et al. 1994; Tessaro
1992). This chronic disease is progressively debilitating to the
host, and may cause reduced fertility and weakness; advanced
cases are fatal (FEARO 1990). The disease manifests similarly
in cattle and bison (Tessaro 1989; Tessaro et al. 1990). Both the
U.S. and Canada perform nationwide surveillance of abattoir
facilities to monitor BTB infection in cattle and domestic bison.
There is no suitable vaccine available for BTB (FEARO 1990;
CFIA 2000; APHIS USDA 2007). Every bison imported into
Canada from the U.S. must be quarantined from the time of
its importation into Canada until it proves negative to tests
for BTB performed at least 60 days after it was imported into
Canada (CFIA 2007). A quarantine protocol has been developed
and an experimental project was attempted to salvage bison
from a BTB exposed population (Nishi et al. 2002b). Although
at first it appeared to be a successful tool for salvaging bison
from an exposed herd, after 10 years, several of the salvaged
animals expressed BTB, and in 2006 all salvaged animals were
slaughtered (Nishi personal communication). There is some
evidence that BTB can be treated in individual animals using
long term dosing with antibiotics, but the duration of treatment,
costs of therapy, and the need for containment make this
option impractical for wildlife. The only definitive method for
completely removing BTB from a herd is depopulation (CFIA
2000; APHIS USDA 2005). The only alternative to depopulation
is controlling the spatial distribution and prevalence of disease
through a cooperative risk management approach involving all
stakeholders. The basic prerequisites for effectively addressing
risk management associated with BBTB in bison are teamwork,
collaboration across professional disciplines, and respect for
scientific and traditional ecological knowledge among technical
and non technical stakeholders (Nishi et al. 2006). BTB can
infect humans, but it is treatable with antimicrobial drugs.
Human TB due to M. bovis has become very rare in countries
with pasteurised milk and BTB eradication programmes.
5.1.7 Bovine viral diarrhoea
Bovine viral diarrhoea (BVD) is a pestivirus that infects a wide
variety of ungulates (Loken 1995; Nettleston 1990). Serologic
surveys in free-ranging and captive populations demonstrate
prior exposure in more than 40 mammal species in North
America (Nettleston 1990; Taylor et al. 1997). The suspected
source of BVD in wild animals is direct contact with domestic
livestock. Infections in wild ruminants, like cattle, are dependent
upon the virulence of the isolate, immune status of the animal
host, and the route of transmission. Infections in cattle are
usually subclinical, but some infections may cause death
or abortions in pregnant animals. Factors influencing the
persistence of BVD include population size and density, herd
behaviour, timing of reproduction, and survivorship of young
(Campen et al. 2001).
Positive serologic evidence was reported for blood samples
from bison in the GYA (Taylor et al. 1997; Williams et al. 1993),
American Bison: Status Survey and Conservation Guidelines 2010 31