Black leg

DR WAQAS NAWAZ
PMAS Arid Agriculture University, Rawalpindi
Pakistan

1. 11-arid-929 11-arid-930 Black Leg

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 ) Black Leg

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. Etiology

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. B ut cases can occur at any time during the year. Susceptibility

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. Clinical Presentation

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 .

7. 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 . Reason for Crepitation

8. 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. Diagnosis

9. 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 . Treatment

10. 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 . Prevention & Vaccination

11. 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 . Credits of Vaccine Development

12. 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 Carcass D isposal