Agriculture Reference
In-Depth Information
up, but the internal form is generally deadly. It is thought to spread from one
sheep to another by the bacteria escaping from ruptured abscesses.
If you notice any kind of abscess, isolate the sheep immediately and have
your veterinarian drain the abscess and test it to determine if it is indeed
C. pseudotuberculosis
. If so, the sheep is probably best culled, unless it is a
high-value animal. In the case of very valuable animals, if the disease is caught
early, the veterinarian may be able to surgically remove all the abscesses.
Never try to drain an abscess yourself. When done improperly, drainage just
spreads the disease to the rest of the fl ock and possibly even to people. There
is a vaccination available, and when you are purchasing new sheep, be aware
that an enzyme-linked immunosorbent assay (ELISA) is available to test for
the disease.
Johne's Disease
A chronic, infectious disease with worldwide distribution, Johne's (pro-
nounced YONE-ees) disease is caused by a hardy bacterium by the name of
Mycobacterium paratuberculosis
. These bacteria are distantly related to those
that cause tuberculosis and leprosy in humans. Unlike most pathogenic bacte-
ria, which die pretty quickly when they're out in the environment, these bugs
have been documented to live up to a year outside a host.
The main symptom of Johne's disease is unexplainable weight loss, despite
reasonable food intake. Weight loss may be accompanied by intermittent diar-
rhea, but this combination of weight loss and diarrhea is easily confused with
other diseases.
Although many animals in infected fl ocks carry the organism, quite a few
develop an immune response that permits survival. It can be tested for by run-
ning a bacterial culture on fecal matter and by having an ELISA done, though
these tests are not 100 percent accurate. Unfortunately, there is no approved
vaccine for sheep.
Listeriosis
Although the bacterium that causes listeriosis
(Listeria monocytogenes)
is a
relatively common soil microorganism, the disease seems only to be associ-
ated with feeding of spoiled silage. If you are feeding silage, make sure that it
is properly ensiled and unspoiled. There are no effective treatments for this
disease, and when an outbreak occurs, the mortality rate is high. Symptoms
include disoriented, circular walking; facial paralysis and drooping ears; low-
ered eyelids; depression; and abortion in late-term ewes.