Download Black Leg Disease - Cairo University Scholars

BLACK LEG DISEASE
MADE BY
Riham Mostafa
alarabawy Nancy
Def:
Also called black quarter, an infectious,
often fatal disease of cattle and sheep,
characterized by painful, gaseous
swellings in the muscles, usually of the
upper parts of the legs
cause:Clostridium chauvoie a rod shape gram
positive, motile, sporulating non capsule
forming
anaerobic
microorganism.
Clostridium chauvoie produces four toxin
which is both necrotizing and hemolytic.
R.O.I:The spores probably are ingested,
pass through the wall of the GI tract,
and after gaining access to the bloodstream,
are deposited in muscle and other tissues (spleen,
liver, and alimentary tract) and may remain dormant
indefinitely.
Pathogenesis :
Cattle
blackleg infection is endogenous. Lesions develop ◦
without any history of wounds, although bruising
or excessive exercise may precipitate disease in
some cases. Commonly, the animals that contract
blackleg are of the beef breeds, in excellent
health, and gaining weight.
Outbreaks occur in which a few new cases are ◦
found each day, sometimes for several days. Most
cases are seen in cattle from 6–24 mo old, but
thrifty calves as young as 6 wk and cattle as old as
10–12 yr may be affected.
Sheep
the disease is almost ◦
always the result of a
wound infection and
often follows some
form of injury such as
shearing cuts,
docking, crutching, or
castration.
Pathogenisis :
Spores by ingestion ---------intestinal mucosa ----blood ◦
circulation and being carried to skeletal muscles and
remaiming dormant .
Under muscular fatigue or trauma to the muscle producing ◦
anaerobic conditions allow spores to activate .proliferate and
produce toxins …app
The toxins cause capillary damage .hemorrhagic edema and ◦
necrosis of myofibers with formation of gas (h2s)
The organism is able to ferment sugar ------gangrene and ◦
toxemia .
PM:
the infected area is composed of black,
dead (necrotic) muscle which is pocked with
gas bubbles and is usually found in the
heavier more active muscle masses of the
animal. A sweetish odor of rancid butter may
be detected from a fresh lesion. Lesions may
occasionally be discovered in the
diaphragm, heart or tongue
Two stages of the disease:
Early stage : there is serohemorrhhagic exudates between necrosed muscles which ◦
appeared dark red .
Late stage : the muscle has aporous appearance due to presence of gases ◦
with the presence of black discolortion due to formayion of iron sulphide
Peticheal hemorrhages on the serous membranes . ◦
Parenchymatous degeneration ---due to toxemia ◦
Edema and hemorrhage on serous cavities . ◦
Black leg. Dark-red skeletal muscle of a
heifer showing hemorrhage, necrosis,
edema and emphysema.
: Black leg disease. Heart muscle
showing dark red hemorrhagic and
emphysematous
CLINICAL SIGNS :Lamness .1
Fever .2
Anorexia .3
Depression .4
Marked swelling of the upper part of .5
affected leg
Skin over the swelling become discolored & .6
dr
The
animal
dies
within
12-36 hours after the
appearance of signs.
Recovery case
GROSS PICTURE :1. The dead animal are usually lying on the affected side. The
carcass is bloating and putrefaction quickly. The lesions
usually involve hind quarters, shoulders, neck, back or lions
and frequently tongue and heart
2. The skin over the affected area is dark red or even black
with crepitating on pressure. The gas is due to formation of
H2S and the black color is due to iron sulphide formation .
In cut section a serosanguineous, foul smell fluid may exude.
3. The subcutaneous tissue is red or infiltrated with
yellowish gelatinous exudate intermixed with
hemorrhages and gas bubbles
4. The incised affected muscles are dark red in
color, swell with rancid odor due to fermentation of
glycogen (Figs 1&2).
5. The regional lymph nodes are enlarged and may be hemorrhagic.
•
6. The heart usually shows ulcerative endocarditis in the left atrium,
bicuspid valve, and inner wall of the pulmonary vein
.
7. Body cavities: The abdominal and thoracic cavities contain
excess fluid which contains variable amounts of fibrin and is usually
blood. stained.
•
8. Other organs: The internal organs undergo degeneration, and the
postmortem decomposition with the production of gas in the liver
occurs rapidly.
•
•
•
MICROSCOPIC APPEARANCE
The muscle fibers show coagulative necrosis
which
infiltrated
with
neutrophils
and
lymphocytes,
cloudy swelling,
and
fatty
change. Moreover, the muscle fibers are
separated by
gas bubbles, edema, and
hemorrhage Gram positive microorganisms are
observed everywhere among the muscle fibers.
The
lymph
nodes
show
hemorrhagic
lymphadenitis
and
emphysema
besides
myocarditis and ulcerative endocarditis.
Lymph node of cattle infected with
black leg disease showing air
bubbles (emphysema). H&E.
Refrences :
http://www.merckvetmanual.com/mvm/generalized_con
ditions/clostridial_diseases/blackleg.html
http://www.thedairysite.com/articles/843/blackleg-incattle/
the book of clinical vetrinary pathology cairo university
http://www.vetmansoura.com/Pathology/bacterial/Diseas
es4.html