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Montana Department of Livestock (DOL) claims it is slaughtering
the Yellowstone bison because they carry brucellosis. This
claim rings hollow in light of a few facts: There has never
been a documented transmission of brucellosis from wild bison
to livestock. Even if buffalo were capable of spreading the
disease, there are no cattle
on these lands from mid-October to mid-June, making brucellosis
transmission impossible.
All bison captured and slaughtered this winter have been bulls,
which are incapable of transmitting the disease. The ten bull
bison slaughtered this week tested positive for brucellosis
antibodies, not infection. Because bison are known to build
natural resistance to brucellosis, these animals may actually
be the strongest, healthiest animals of the herd. The overwhelming
majority of bison slaughtered according to these test results
don't actually carry the disease.
Most bison that test positive at the capture facility test
negative under the more accurate post-slaughter necropsy.
The DOL is using a new methodology for detecting antibodies
to brucellosis in wild bison called the Fluorescent Polarization
Assay (FPA). This testing method involves the use of antigens
tagged with a fluorescent material which detect IgG (immunoglobulin
G) type antibodies to brucellosis and bind with them. Binding
between the antibody and the tagged antigen results in an
increase in polarization which is detected by the analyzer
and reported as a quantitative result. This result is interpreted
as positive or negative based on certain cut-off values. Studies
have established that the specificity and sensitivity of this
test were found to be much higher when compared to Particle
Concentration Fluorescence Immunoassay and the CARD test (Nielsen
et al 1998).
However, in spite of the advanced technology of this testing
method it is only capable of detecting IgG (long term immunity)
antibodies, not the presence of brucella organisms. The major
advantage of FPA over the Card test is that it will detect
a quantitative level of antibodies, which may or may not directly
correlate to the presence of an infection, whereas the Card
test simply detects the qualitative presence or absence of
antibodies. Although the DOL has finally begun using advanced
technology to detect brucellosis antibodies in wild bison,
they are still unable to correlate their test results to prove
actual infection.
Culture of tissues from slaughtered bison are no longer being
done to confirm their testing results. In spite of these facts,
DOL continues to use the results of both the FPA and the Card
test to send low risk bison (i.e. bulls) to slaughter.
Even if only the Card test is positive and the more specific
FPA is negative, a buffalo will be sent to slaughter. Why
is DOL spending thousands of tax payer's dollars on new technology
if it will not be properly utilized and potentially save uninfected
bison from needless slaughter?
Sources;
Nielsen, K., Gall, D., Lin, M., Massangill, C., Samartino,
L., Perez, B., Coats, M., Hennager, S., Dajer, A., Nicoletti,
P., Thomas, F. 1998. Diagnosis of bovine brucellosis using
a homogeneous fluorescence polarization assay. Veterinary
Immunology and Immunopathology. 66(1998) 321-329.
Perkin/Elmer Life Sciences, web site. Accessed 01/10/02.
Lumigen web site. Accessed 01/10/02. USAHA web site information
from 1997.
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