Anthrax

What is it?

Anthrax is a disease primarily found in animals, caused by the bacterium Bacillus anthracis. Humans can be infected with it when they are exposed to infected animals, tissue from infected animals or exposed to the spores of the bacterium.The commonly affected animals include cattle, sheep, goats, camels, antelopes and other herbivores. Anthrax was described more than 3,500 years ago and may have been to blame for two of the plagues of Egypt in 1491 B.C.

What are the causes?

The bacterium, Bacillus anthracis, is the causative organism. Under a microscope with appropriate staining, the bacteria look like small rods. The spores are usually spherical structures, smaller than the bacteria, and are the dormant form of the bacteria. They can survive in the soil for years, and can withstand hot or cold temperatures.

What are the symptoms?

The symptoms vary depending on the route of infection. Symptoms usually appear within seven days. Cutaneous anthrax: Most anthrax infections (about 95 percent) occur when the bacteria or spores enter a cut or scrape on the skin. Skin infection begins as a raised, itchy bump that resembles an insect bite but within 1-2 days develops into a vesicle and then a painless ulcer, usually 1-3 cm. in diameter, with a characteristic black necrotic (dying) area called the eschar in the center. The nearby lymph glands swell. About 20 percent of untreated cases of cutaneous anthrax are fatal, but death is rare when it is treated. Inhalation anthrax: It is also known as woolsorter’s disease. The initial symptoms may resemble a common cold. Later on the symptoms may progress to breathing problems and shock. Untreated inhalation anthrax is usually fatal. Intestinal anthrax: The intestinal form is rare and is characterized by swelling of the intestines. The initial symptoms include nausea, loss of appetite, vomiting and fever, followed by abdominal pain, vomiting of blood, and severe diarrhoea. Intestinal anthrax may be fatal in 25-60 percent of cases.

How is the diagnosis made?

The diagnosis can be made at most microbiology laboratories by smear examination and isolating the bacteria from the blood, skin lesions, or respiratory secretions by culture. Bacillus anthracis is an organism which is very easy to culture and identify.The anthraxin skin test, consisting of subdermal injection of a commercially produced chemical extract of an attenuated strain of B. anthracis, is available for the diagnosis of acute and previous cases of anthrax. It can also be diagnosed by looking for specific antibodies in the blood or by molecular biology techniques like PCR.

What is the treatment?

It should be remembered that cattle or sheep (together with guinea pigs) are extremely susceptible to infection, as few as 1—10 spores being sufficient to produce the disease. The infective dose for humans ranges from 100,000 to 1000 spores. It is estimated that inhalation of 100,000 spores would infect 50% of the people exposed to the spores.

What are the prevention?

An effective vaccine is available - about 93 percent effective in protecting against anthrax. But supplies are limited, and are usually used to immunize the armed forces. Taking antibiotics as a preventative measure is foolish. It will do more harm than good to take antibiotics without medical supervision. The antibiotics commonly used for treatment are effective against other illnesses also and their misuse may lead to development of resistance and consequently they will not work against other diseases. Prophylaxis for asymptomatic patients with suspected exposure to anthrax spores can be achieved with a 6-week course of doxycycline or ciprofloxacin.

DoctorNDTV Team

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