disease outbreak in farmed elk*
A new elk raising
facility was built early in the 1990s on land that had not housed livestock for
more than 20 years. Eighty elk (Wapiti wapiti) were purchased from various
herds in the United States and Canada. No unusual or extensive health problems
were noted prior to the Johne's disease outbreak.
One winter, a 3
year old female elk was introduced without quarantine into the herd. She suffered
various ailments for the next 4 months, including lameness, weight loss and diarrhea.
Several treatments for gastrointestinal parasites did not change the animal's
condition. A complete blood count and chemistry panel were not diagnostic. The
"Johne's test" requested by the veterinarian was negative (the diagnostic laboratory
receiving the sample ran a complement
fixation test). She was moved back and forth several times from a 16 acre
group pen to a pen used to isolate sick animals.
That spring she delivered a stillborn calf and acted as a "nursemaid" to the 31
calves born in the group pen. She died in early summer. Johne's disease was diagnosed
at necropsy and confirmed by bacterial isolation of the organism from tissue samples.
Eleven of 31 calves
born and held in a pen with the M. paratuberculosis infected adult cow
developed severe clinical signs (emaciation and diarrhea) and died of Johne's
disease before they reached 2 years of age. The status of the remaining 19 calves
is unknown. Infection of the calves was thought to have been
through fecal-oral transmission of the organism via a muddy wallow frequented
by both the calves and the infected adult. Cross-fostering by the infected adult
may also have contributed to the infection, as more than one calf may have nursed
from the cow.
the diagnosis of paratuberculosis was based on culture
of tissues, serology and histopathology.
After a diagnosis
of Johne's disease was made in the yearlings, the group pen became the quarantine
site for any animals with signs of Johne's disease. After all the yearlings had
left the premises, the soil in the pen was turned and the pen held empty for a
year. This pen was then to be used solely for adult animals on the presumption
that, as in cattle, mature elk will be less susceptible than young stock to infection
from the few organisms that may have remained.
All the animals
held in the pen (i.e. the cows of the affected calf crop) at the time of the outbreak
plus resident bulls were tested one year after the outbreak in the yearlings.
One fecal sample was collected from each adult animal; each sample was negative
by the BACTEC culture method. A number of annual negative tests are necessary
before confidently concluding that the remaining animals on the premises are free
of M. paratuberculosis infection.
||Elk are susceptible
to M. paratuberculosis infection, with clinical signs of disease appearing
at a younger age in this outbreak than is typical for cattle.
|| Microscopic lesions
resembled those found in cattle and were characterized by granulomatous inflammation
of ileum, jejunum and mesenteric lymph nodes.
testing is important to limit the likelihood of introducing the disease to uninfected
|| Johne's disease
does not yet appear to be a common problem for the elk farming industry as a whole
but the disease can be economically ruinous to individual herd owners.
H. Steinberg, K. Russow, G.R. Ruth, and M.T. Collins. 1998. Epizootic of paratuberculosis
in farmed elk. J. Am. Vet. Med. Assoc. 213:13201322