Anthrax

Anthrax is originated from Greek word Anthrox means coal. Other names for this disease are spleenic fever, woolsorter’s disease. Locally it is called as golle or sut. It is an acute, contagious and septicemic disease. Highly fatal and affecting a wide range of mammalian species including human beings.

Before the availability of an effective vaccine, anthrax was one of the most important causes of death in livestock throughout the world.  The results of national epidemiological survey of important diseases of livestock in Pakistan has indicated that anthrax is one of the leading causes of death among sheep, goat cattle in hilly and desert areas.

Causative Agent:
Anthrax is caused by a bacterium known as Bacillus anthracis. The organism is G +ve, non motile, aerobic, facultative anaerobe and spore forming. There are two forms of this organism: vegetative and spore forming. Vegetative form occurs inside the body of affected animals and is responsible for producing clinical signs and pathological lesions. The spore formation occurs outside the body of host and is the result of exposure of vegetative form to oxygen.

Transmission:

• Mostly animals are infected while grazing in areas that have previously experienced anthrax.

• The spores are also transmitted through the consumption of contaminated water, hay, and fodder.

• Eating of bone meal and blood meal of infected animals also cause transmission.

• Eating of dry fodder or spiky grass produces lesions in gastrointestinal mucosa, and the chances of infection are increased.

• Flies are also a source of transmission.

Clinical Findings:
Its incubation period is 1-2 weeks, some says 7 weeks. Most common sign of disease is sudden death. There are three forms of disease:

Peracute:
It is most common at the beginning of outbreak. Animals are found dead without signs. Course of disease is only two hours. Signs may be fever, dyspnia, congestion of mucosa and muscle tremor and animal dies after convulsion. After death there is discharge of blood from natural orifices (mouth, nostrils, anus, vulva etc.).

Acute:
Course of disease is 48 hours. There is severe depression, increased body temperature upto 107 ^oF, rapid and deep respiration, and congested mucosal lining.

Pathogenic signs are congestion of mucous membrane, hemorrhage from natural orifices, increased heart rate, animal off feed, ruminal stasis, abortion in pregnant cows, blood stained or deep yellow milk, diarrhea, dysentery, and local edema of tongue.

Chronic:
Chronic infection is characterized by localized, subcutaneous, edematous swelling that can be quite extensive. Areas most frequently involved are ventral neck, thorax, and shoulders.

Diagnosis:
It is based on the history of the occurrence of disease in an area, clinical signs, and necropsy findings. Sudden death in an animal without prior symptoms should lead to suspicion of anthrax and bloody fluid exuding from the nose and mouth or anus of living or dead animal is particularly suggestive of anthrax.

Postmortem is not allowed in case of anthrax. To prepare blood smear, blood is obtained from ear by giving incision. Blood film should be dried and fixed by heat or immersion for one minute in absolute methanol and stained with polychrome methylene blue. Then it is washed after thirty seconds into hypochlorite solution. After drying the slide, it is examined under microscope for reddish purple capsular material and deep blue Bacilli. This reaction is termed as M- Fadyean reaction.

Treatment:
Because this disease is rapid in onset and with large mortality rate (90%), this is insufficient to initiate treatment before death. If anthrax is suspected, segregation of animal should be done. Early supportive and antimicrobial therapy is useful and Bacillus anthracis is highly susceptible to a wide range of antibiotics including benzylpenicillin, tetracycline, and ciprofloxacin. First dose of antibiotic should be administered intravenously and then intramuscularly for 5 days. Prognosis is not favourable and no time to treat the animal.

Differential Diagnosis:
In cattle and buffalo differentiate it from acute fatal blot, per acute babesiasis, gross tetany, black quarter, acute poisoning, and enteritis. Anthrax should be considered in differential diagnosis when an animal dies after having observed apparently good health during the preceding 24 hours. 

Control Strategy for Anthrax:
Control measure is aim to break the cycle of infection. The important thing is to correct the disposal of carcasses. When an animal dies inside a shed, paddle or barn, its carcass should be received for burial or incineration. Plug all the natural orifices properly before disposing carcass. Burial should be away from water supply and pasture. The pit should be at least 180 cm deep. The top layer after burying should be covered with unslacked lime. Decontaminate the area, bedding, unconsumed feed, and room. Dip the equipments in 4 % formaldehyde solution for 12 hours.

Vaccination:
Veterinary Research Institute (VRI), Lahore has developed anthrax spore vaccine. It imparts solid immunity for one year. Its dosage in cattle and buffalo is 1 ml subcutaenously. Vaccination should not be done in area where disease does not occur. During vaccination one should not be exposed to vaccine by needle prick.

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