|
Clostridium novyi
(Black Disease)
Doug
Stearn, DVM
Staff Veterinarian
Black disease is caused by the bacteria Clostridium
novyi. This
disease causes acute toxemia in cattle, sheep and occasionally
pigs and horses. It
is always fatal in cattle and sheep.
The bacteria is found worldwide, but the disease is
most prevalent in
areas where liver flukes are found.
Black disease gets its name from the dark or black
appearance under the skin due to rupture of the capillaries in
the subcutaneous tissue.
Clostridium
novyi bacteria is present in soil and is ingested by the
animal as it grazes in pasture.
The bacteria produces spores which can gain entry into
the body from the intestinal tract.
The spores are then transported to the liver where they
lie dormant. Once
the spores are in the liver no disease process is noted until
there is injury to the liver.
Usually, the inciting cause of injury to the liver are
liver flukes which migrate through the liver creating an
anaerobic environment for the spores to proliferate.
Once the spores start to grow, they release necrotizing
toxin which causes
local tissue destruction and more diffuse damage to the
vascular system. Clinical
signs in cattle are sudden, severe depression, reluctance to
move, absent rumen sounds, muffled heart sounds and low body
temperature. Typically,
the animal dies within one to two days.
In sheep, death is typically sudden with no outward
signs noted. Black
disease has a seasonal occurrence because of
fluctuations in liver fluke and host snail populations.
The disease usually occurs in summer and autumn.
The first frost of the fall usually will stop the
cycle.
Post mortem findings in cattle with Black
disease include frothy blood from the nostrils, black
subcutaneous tissues, swollen liver with areas of necrosis,
blood stained serous fluid in the pericardial, pleural and
peritoneal cavities. Diagnosis
of Black disease is through culture of the liver and the
characteristic lesions noted on necropsy.
One method of
control of the disease is through managing
liver flukes with deworming and control of the snails
with molluscicides. The
better method of controlling the disease is through a good
vaccination program utilizing Colorado Serum Company’s Essential
4 Clostridial toxoid.
Vaccinations are usually done in early summer prior to
seasonal occurrences of liver flukes and their host snail
population. Annual
boosters are recommended.
Calves are vaccinated at two to
three months of age and should be revaccinated at four
to six months of age.
|
