Blackleg disease, also known as black quarter, is caused by the bacterium Clostridium chauvoei. It causes acute, infectious myositis in cattle and sheep. The bacteria forms spores that can survive in soil for years and are ingested, passing through the intestinal wall and entering the bloodstream. The spores then deposit in muscle tissues where they remain dormant until muscle trauma or fatigue activates them, causing necrosis, edema, and gangrene. Clinical signs include severe lameness, swelling of the upper leg, depression, and high fever. Death often occurs within 12-36 hours. Diagnosis is based on clinical signs and identification of the bacteria. Treatment involves antibiotics but success is low.

1. Blackleg Disease
(Black quarter)
Chorray Maar

2. Definition
 acute, infectious, non-contagious, febrile
 cattle and sheep
 Myositis—upper part of leg
 emphysematous swelling

3. Etiology
 Clostridium chauvoei
 gram positive, spore forming, rod shaped
 spores resistant to environmental changes and
disinfectants
 persist in soil for years

4. Route of Infection
 Ingested spores
 pass wall of GI tract/erupting teeth
 access to bloodstream
 deposited in muscle and other tissues (spleen, liver,
and alimentary tract)
 remain dormant indefinitely

5. Occurrence
• Worldwide
• When disease occurs number of animals affected
• Enzootic in particular areas
• Group of farms to individual in field
• case fatality rate 100%
• seasonal—warm months
• Excavation of soil

6. Risk factors
Cattle
infection is endogenous
 Lesions without history of
wounds
bruising or excessive exercise
precipitate disease
Most cases in cattle 6–24 m
old
calves as young as 6 wk
cattle as old as 10–12 yr
Sheep
always result of
wound infection
shearing cuts,
docking, crutching, or
castration
Navel wound
Lambing injuries
Fighting injuries
After Vaccination

7. Pathogenesis
 Spores by ingestion intestinal mucosa blood circulation
skeletal muscles and remain dormant
 Muscular fatigue or trauma to the muscle
 Producing anaerobic conditions
 Spores activate, proliferate, produce toxins
 necrotizing myositis / toxemia
 Toxins --- capillary damage, hemorrhagic edema and necrosis
 Gas production------gangrene and toxemia .

8. Clinical Findings
 Sever lameness
 Pronounced swelling of upper part of leg
 Depression
 Complete anorexia
 Ruminal stasis
 High temperature and pulse rate

9. Clinical Findings
 Early stages --- swelling hot and painful
 Later--- cold and painless
 Edematous and emphysematous
 Crepitation on palpation
 Discolored, dry and cracked skin

10. Clinical Findings
 Lesions on base of tongue, heart muscles,
diaphragm, brisket, udder
 Condition develops rapidly
 Death12-36 hrs after appearance of signs
 deaths without signs / clostridial cardiac myositis

11. Diagnosis
 Clinical signs
 No constant changes in hemogram and serum
chemistry
 Demonstration of organism
 Samples: Muscle in air tight container
Air dried impression smears
 PCR

12. Necropsy findings
 Lying on the side with the affected hind limb stuck
out stiffly---characteristic position
 Bloating and putrefaction occurs quickly
 Blood stained froth from nostrils and anus
 Incision ---- dark red to black swollen tissue with
rancid odor---gas bubbles

14. 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

15. 15http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=1404
Dark red to black of muscle often with a distinct odor of sour milk

16. 16

17. False blackleg
 C. septicum and C. novyi
 Mixed infection C. chouvoei and C. septicum

18. Differential diagnosis
 Malignant edema
 Anthrax
 Lightning stroke
 Bacillary hemoglobinuria

19. Treatment
 Penicillin--- Large doses (40,000IU/kg BW)
 Surgical debridement of the lesion including
fasciotomy
 Recovery rate is low
 Blackleg antiserum

20. Control
 Vaccination in enzootic areas
 Booster vaccination
 Prior to anticipated danger period

21. Control
 Maternal immunity --- 3 months
 In outbreak ---vaccinate unaffected animals
 Penicillin at 10000IU/kg BW IM
 Carcasses destroyed by burning or deep burial