T,

MONTANA STATE LIBRARY

S 616.9654 F2tmb 1993? c.1
Trichinosis in Montana bears /

3 0864 00084415 2

richinosis is a parasitic disease
of humans and other mammals
which results from ingestion of
larvae of the muscleworm
(Trichinella spp.) in infected
animal tissue. The nematode
responsible for this infection was
first discovered in the muscles of
a human patient in 1835. The
mode of infection was studied
extensively during the latter part
of the 19th century and was
f ound to consist of a unique life
cycle in which all stages of the
parasite occur in a single host.

T,

1

richinosis in wild animals has
been studied extensively; at least
22 species of carnivorous
mammals and a few predatory
birds have been implicated in the
transmission of the infection in
North America. Predation and
scavenging are thought to be the
two principal mechanisms by
which the infection is acquired.
Carcasses of infected carnivores
are the major source of exposure
for wildlife and humans. In
Montana, bears are implicated as
the greatest potential source of
infection since many are
consumed by hunters each year.
More than 10 % of human
trichinosis cases in the United
States are traced to infected
bear meat.

How prevalent is
Trichinosis in
Montana Bears?

Extensive testing of black and grizzly bears
during cooperative studies by MSU and
MDFWP has been conducted during the past
30 years. Over 500 black bears and 300
grizzly bears were tested. Sixty-four percent
of the grizzly bears and 15 percent of the
black bears have tested positive for trichinosis.
The older a bear is the more likely that it will
have been infected. Most bears over 15
years of age are infected.

T

photos by W.J. McRae

here is also a gradient of prevalence in
Montana bears with high infection rates in
the northwest and lower infection rates in the
southcentral portions. Counties with high
prevalence include Flathead, Lincoln and
Sanders counties in northwestern Montana.

BKAR INFECTION RATKS
in Montana

100/

80-

■ Grizzly Bear
□ Black Bear

2

+-»

60-

o

Q.

c

<D

40-

O

£

20-

Southeast

Region 1 Region 2 Region 4 Region 3 Region 5 Yellowstone

Administrative Region

A,

dull worms in the intestine
during the early stages of the
disease produce symptoms
resembling food poisoning, i.e.,
severe diarrhea. As larvae enter
the circulation and migrate
through skeletal muscles and
other tissues, elevated body
temperature, toxemia, focal
hemorrhages and eosinophilia
become evident. Ten to 30 days
after exposure severe muscle
pain, stiffness of the neck,
swelling around the eyes and
inflammation occur. There is
currently no effective treatment
for the intramuscular stage of the
disease. In bears, a response
similar to larval migration in the
tissues occurs, but acute disease
has not been observed in
experimentally infected animals.

5>

C/5

C/5

LIFE CYCLE
of TRICHINELLA SPIRALIS

INFECTED BY
IMPROPERLY
COOKED MEAT

develop to
adult worms

When infected muscle
is eaten, larvae excyst
in intestine and...

ADULTS IN
SMALL INTESTINE

INFECTED
MEAT

and
encyst.

Female deposits
larvae in tissues of
intestine...

LARVAE carried by
blood to skeletal
muscle...

E

radication of Trichinella
in wildlife is unlikely
because scavenging and
predation are the principal
mechanisms of transmis-
sion. For bears these are
natural and essential
feeding strategies. Many
other carnivores including
mountain lion, wolverine,
pine marten, lynx, bobcat,
fisher, otter, coyote, wea-
sel, badger, and fox also
act as a reservoir for
Trichinella larvae.

you hunt and eat bear meat
some simple precautions will
prevent infection. Thorough
cooking of the meat at tempera-
tures exceeding 165° F. will kill
the larvae. However, freezing
will not kill the organism. Curing
by itself will also not kill larvae
^jq but curing along with smoking
seems to kill the parasite.

_ eat samples from hunter

©£) killed bears can be tested at the

MSU Veterinary Molecular
^ Biology Laboratory. Samples can
be submitted for free testing
through MDFWP offices and
> | personnel or can be mailed to:

O

(im^ D. E. WORLEY

Vet. Molecular Biology
Montana State University
Bozeman, MT 597 1 7

o submit a sample cut a 4-5
inch portion from the tongue. If
tongue isn't available cut a
golfball-sized piece of muscle
from the head or leg. Place the
sample in a plastic bag labeled
with the date of kill, location of
kill, sex of bear, and your address
and phone number. You will be
notified of the results within 2-4
days. Special mail kits for sub-
mitting samples are available at
Montana Dept. of Fish, Wildlife
& Parks Regional offices.