Black Quarter:

Synonyms: Black leg, Quarter Ill, Symptomatic anthrax, Emphysematous gangrene

• It is an acute infectious but not contagious disease of cattle, sheep, goat.
• It is characterized by development of focal gangrenous and emphysematous myositis. This gives rise to crepitation and sero-hemorrhagic swelling in the heavy muscles like gluteal muscles.
• It produces severe toxemia with very rapid course and high mortality.

Etiology:

• Clostridium chauvoei
• Gram-positive, rod shaped, spore forming anaerobe
• Size; 0.6 micron in diameter and 3-8 µ in length
• Spores are resistant to heat, desiccation and disinfectants.
• Organism can be destroyed by 3% formalin in 15 minutes and by 2% bichloride of mercury in 10 minutes.

Epidemiology:

• Young animal of 6 months to 2 years old are most susceptible to infection.
• They are more frequent during warm, humid weather, especially in rainy season when soil contamination is higher.
• It is wide spread in almost all tropical countries of the world.
• Disease spreads rapidly following heavy rainfall.
• Disease was first recognized by Billinger in 1975, wide spread in USA
• Infection rate of 85% has been recorded from Madras, Bombay, Hyderabad.
• morbidity can range around 30–50% in non-vaccinated herds while mortality reaches upto 24% in affected cattle.
• Disease is sporadic in nature in Nepal.

Transmission:

• Disease spreads from contaminated soils.
• Ingestion of infected feeds or contamination of wounds
• In sheep, bacteria gain entry through shearing, docking, lambing and castration.
• Wounds due to fighting, naval infection, vulva and vaginal infection at birth may cause local lesions.

Pathogenesis:

Clinical Findings:

• Incubation period: 2-5 days

Cattle:

• Rise in body temperature as high as 106-108°F
• Loss of appetite, suspended rumination
• Stiffness or lameness in one of the limbs.
• Characteristic swelling develops in one of thick layers of muscles.
• Lesion are commonly found on thigh, buttocks, shoulder, necks and lumbar region
• Swellings are hot and painful in early stage and become cold and painless latter.
• Muscle tissue are swollen, dark in color and turn dry.
• Gas pocket arise in muscles. On pressure, swellings emit crackling or crepitation sound due to emphysema.
• Labored breathing, accelerated pulse rate; 100-120/min
• Finally, temperature drops and animal dies within 12-48 hours after manifestation of clinical signs.

Sheep:

• In sheep, there is extensive hemorrhagic edema in the subcutaneous tissues following wound.
• Complete loss of appetite, high rise of temperature, profound depression
• Lameness may be present in some sheep.
• No crepitation in sheep
• Swelling of head and neck, bleeding from nose
• Death occurs within 24-48 hours post infection.

Horse:

• Edema of pectoral muscles
• Stiffness of gait
• Ataxia

PM lesions:

• Large crepitating swelling are most characteristic feature of necropsy.
• Lesion are found in muscles of shoulder, thigh, neck, tongue, diaphragm and myocardium.
• Affected muscles are infiltrated with yellowish exudate.
• Gas bubble accumulate between muscle fibres.
• Affected tissues turn black.
• Rancid odor emanates from muscles.
• Blood stain discharge may ooze from nostrils.
• Accumulation of fluid in pericardium.
• Conjunctival mucus membrane become congested
• Liver, kidneys, lungs and spleen show yellowish foci and hemorrhage.
• Entire body assumes a bloated appearance.
• In some cases, bloodish frothy discharge from natural orifices.

Diagnosis:

• In field condition, disease is usually diagnosed based on history, clinical signs and PM findings.
• In lab, disease may be diagnosed by following methods:
  • Microscopic examination of smear from affected tissues reveals gram+ve rods.
  • Culture of organism in anaerobic media
  • Animal inoculation test: Affected tissue are grinded, titrated with sterile saline and filtered. These filtrates are injected into gluteal muscles of guinea pig @ 1ml. animal dies within 48 hours.
  • FAT

Differential Diagnosis:

1. Anthrax: Crepitation sound is absent, Splenomegaly
2. Bacillary hemoglobinuria: No crepitation, liver infarcts, hemoglobinuria
3. Sweet clover poisoning: Presence of excessive fluctuating hemolytic swelling that contain blood. Pit on pressure, no crepitation.

Treatment:

• Penicillin is considered drug of choice. Penicillin are injected into affected muscles @ 2000-4000 units/lb body weight per day.
• Crystalline penicillin may be given through IV route followed by procaine penicillin through IM.

Control Measures:

• Carcass should be destroyed by burning or burying.
• Calf and sheep shouldnot be allowed to graze in endemic pasture.
• All of animals in endemic zones should be vaccinated with suitable vaccine.
• Immune serum is given in animals @ 15 ml for cattle and 10 ml for sheep.
• Polyvalent BQ vaccine is given through SC route @ 5ml in cattle and buffaloes and 2-3 ml in sheep and goat.
• Combined HS and BQ vaccine is administered @ 5ml SC in large animal and @2ml SC in small animal.