Blackleg is an acute, infectious disease most commonly caused by the bacteria Clostridium chauvoei that affects cattle, sheep, and goats worldwide. It causes swelling of heavy muscles and is often fatal within 1-2 days. The bacteria likely enters via ingestion and remains dormant in muscle until stress causes an outbreak. Vaccination is the most effective prevention, with annual boosters recommended for young livestock in high-risk seasons.

1. 11-arid-929
11-arid-930

2. • Blackleg is an acute, infectious, highly fatal disease of
animals, characterized by emphysematous swelling,
commonly affecting heavy muscles.
• It is found worldwide. It is seen in livestock all over the
world, usually affecting cattle, sheep, and goats. It has
been seen occasionally in farmed bison and deer.
• Other names for it in literature are Black quarter, quarter
evil, or quarter ill (Latin: gangraena emphysematosa)

3. • Blackleg is most commonly caused by Clostridium
chauvoei, but C. feseri and other clostridial species can
be isolated from some lesions.
• C. chauvoei is Gram-positive, rod-shaped, anaerobic,
and motile, spore forming bacteria.
• The organisms 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.

4. • Most losses due to blackleg occur when the cattle are
between the ages of six months and two years.
• Typically, cattle that have a high feed intake and are
well-conditioned tend to be the most susceptible to
blackleg.
• Furthermore, many blackleg cases occur during the hot
and humid summer months or after a sudden cold
period.
• But cases can occur at any time during the year.

5. • In cattle, blackleg infection is endogenous. Lesions
develop without any history of wounds, although bruising
or excessive exercise may precipitate disease.
• Commonly, the animals that contract blackleg are of the
beef breeds, in excellent health, and gaining weight.
• Usually, onset is sudden, and a few cattle may be found
dead without premonitory signs.
• When infection begins, the animal may develop a fever,
and the affected limb can feel hot to the touch.
• The limb usually swells significantly, and the animal can
develop lameness on the affected leg.

6. • Crepitation (the sensation of air under the skin) can be
noticed in many infections, as the area seems to crackle
under pressure.
• Characteristic edematous necrosis and crepitant
swellings develop in the hip, shoulder, chest, back, neck,
or elsewhere.
• As the disease progresses, the swelling enlarges and
the skin becomes cold and insensitive with decreased
blood supply to affected areas.
• General signs include prostration and tremors.
• Death occurs within 12–48 hr.

8. • C. chauvoei can produce a large amount of gas as a
metabolic byproduct when growing and reproducing.
• This gas builds up in infected tissue, usually large
muscles, and causes the tissue to make a crackling or
popping sound when pressed.
• Large gas-filled blisters can also form, which can be
extremely painful as they build up in the tissues.

9. • A rapidly fatal, febrile disease in well-nourished young
cattle, particularly of the beef breeds, with crepitant
swellings of the heavy muscles suggests blackleg.
• The affected muscles are dark red to black and dry and
spongy, have a sweetish odor, and are infiltrated with
small bubbles but little edema.
• The lesions may be seen in any muscle, even in the
tongue or diaphragm.
• Field diagnoses are confirmed by laboratory
demonstration of C. chauvoei in affected muscle
• The fluorescent antibody test for C. chauvoei is rapid
and reliable.

12. • Treatment is generally unrewarding due to the rapid
progression of the disease.
• But penicillin is the drug of choice for treatment and
treatment is only effective in the early stages and as a
control measure.

13. • Vaccination is the most common, cheapest, and
efficacious preventative measure taken against blackleg.
• A multivalent vaccine containing C. chauvoei, C.
septicum and C. novyi antigens is used.
• Calves 3–6 month of age should be vaccinated twice, 4
weeks apart, followed by annual boosters before the
anticipated danger period (usually spring or early
summer).
• Burning the upper layer of soil to eradicate left-over
spores is the best way to stop the spread of blackleg
from diseased cattle.

14. • Dr. Oliver Morris (O.M.) Franklin developed the blackleg
vaccine and the method of vaccination at Kansas State
Agriculture College using live cattle in 1916.

15. • When an animal has died as a result of the blackleg
disease:
 Burn the carcass or bury it deeply with lime
 Burn any contaminated materials, including feces
 Disinfect any contaminated areas
 Do not conduct a necropsy or any biopsy on the animal
 Do not feed the carcass to any other animal(s)
 Promptly contact the state livestock sanitary official