|
Short
answers to common
What
is Johne's disease and
|
|
||||||
 What is Johne's disease and what kind of animals get Johne's disease?
Johne's disease
occurs in a wide variety of animals, but most often in ruminants. Ruminants are
hoofed mammals that chew their cud and have a 3-4 chambered stomach. Some of the
more common ruminants are: cattle, sheep, goats, deer, antelope, and bison. Johne's
disease has been reported in all of these animals but is most commonly seen in
dairy cattle.
On the left task bar choose the animal under "area of interest" and
take a specific topic or you may choose the animal below and see the Frequently
Asked Questions (FAQs) for that species.
Johne's
disease occurs worldwide. In the U.S. it is estimated that 7.8%
of the beef herds and 22% of the dairy herds are infected with M.
paratuberculosis. Infection rates in cattle in other countries
are generally similar. The disease has been reported in sheep, goats,
elk, deer, bison, llamas and wild ruminants in zoos but accurate
estimates of the number of infected animals are not available.
M. paratuberculosis infects the last part of the small intestine (called the ileum) and causes a certain kind of inflammation called granulomatous inflammation. This inflammation thickens the intestinal wall, preventing it from functioning normally. This, among other factors, causes diarrhea and poor absorption of nutrients. As a result, even though animals will seem to be feeling and eating well, they will rapidly lose weight.
There
are three common ways to test animals for Johne's disease: culture
of fecal samples, DNA probe on fecal samples, and blood tests for
antibodies to M. paratuberculosis. It is best to consult
with your local veterinarian about testing. (Because testing strategies
are somewhat different for each animal species, visitors to this
site are advised to seek detailed information by first selecting
an animal species and then choosing "Diagnosis" from the menu on
the left). The majority of the research and the largest number of
types of tests are available for cattle. Visitors will therefore
find the most extensive amount of information about testing by viewing
the Dairy-Diagnosis section
of this site.
Methods
for Johne's disease control depend on the type of animal and the
patterns of husbandry. In principle, two strategies must be employed
at the same time:
Although
few studies report attempts to treat Johne's disease with antibiotics,
it is probably not curable. If it can be cured, it will likely require
use of multiple antibiotics administered for a year or longer. For
most animals, this is cost-prohibitive.
For more detailed information visit the page on "Antimicrobial
Therapy".
This is a very
controversial subject. There is a human disease called Crohn's disease that resembles
Johne's disease. Crohn's disease most commonly affects people 15 to 35 years old.
It is a chronic diarrheal disease that has no known cause and no known cure. Recent
reports in the medical literature indicate that 30 to 75% of patients with Crohn's
disease test positive for M. paratuberculosis. A few laboratories have
grown M. paratuberculosis from a few Crohn's patient specimens. However,
no connection has been shown between contact with animals with Johne's disease
or milk consumption and Crohn's disease. A detailed discussion of this topic can
be found in "Zoonotic Potential"
on this website. |
|||||||
What
causes the signs of Johne's disease?
Johne's
disease typically enters a herd or flock of animals when an infected,
but healthy-looking, animal is purchased. The infection then spreads
to other animals, often without the owner's being aware of it. Eventually,
perhaps after several years, the owner recognizes signs of the disease
in a number of animals. Individual animals get infected by close
contact with other infected animals, that shed the bacterium in
their manure. Most often, the infection is acquired by eating material
contaminated with M. paratuberculosis when animals are
very young. Young animals are far more susceptible to infection
than are adults. Ingestion of the bacterium occurs when the newborn's
environment is contaminated with manure from an infected adult animal,
or by drinking milk from an infected animal. The milk may become
contaminated from the environment (manure-stained teats) or, in
the advanced stages of the infection, the bacterium is shed directly
into the milk. This has been shown to occur in dairy cattle and
is presumed to occur in other species as well. After infection,
many months or years go by until the infected animals shows signs
of Johne's disease.
The
best way to avoid this chronic infectious disease is to be as certain as possible
that animals brought into the herd are not infected with M. paratuberculosis.
This is not always easy.
  |
||||||
 |
||||||
 |
 |
 |
|
 |
|
 |