11-arid-929

11-arid-930

• 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)

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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