Anthrax has become a current, important problem over the last few weeks as a result of the emergence of the disease (at present 16 confirmed, 6 suspected), with four deaths, in the United States of America, and the fear that it is being used as an agent in biological warfare.
Anthrax is a disease caused by the spore- forming bacterium Bacillus anthracis that normally resides in the soil, in the form of microscopic spores. Anthrax pores usually possess thick walls enabling the bacilli to withstand unfavourable environmental conditions, making them difficult to destroy because they are very resistant to heat, requiring prolonged exposure to high temperatures to destroy them. Anthrax spores are invisible, odourless and tasteless. The spores are so tiny that millions would fill a thimble.
Anthrax spores germinate when they enter an environment rich in amino acids, nucleosides, and glucose, such as that found in the blood or tissues of an animal or human host. The bacterium, which looks like a bamboo under a microscope, does not survive long outside of an animal or human host. This contrasts with the hardy properties of the anthrax spore, which can survive for decades in the soil.
Anthrax is most common in agricultural regions, including South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean and the Middle East. The anthrax bacterium is found in wild and domestic animals (cattle, sheep, goats, camels, and other herbivorous animals that feed on grass and herbs).
Anthrax can occur in three forms: cutaneous (skin), inhalation, and gastrointestinal. Humans can become infected with anthrax by handling products from infected animals or by inhaling anthrax spores. Anthrax can also be spread by eating undercooked food from infected animals. Direct person-to-person transmission of anthrax is extremely unlikely to occur.
The symptoms of the disease vary depending on how the disease was contracted, but symptoms usually occur within seven days after exposure to the anthrax spores.
Most (about 95 per cent) anthrax infections occur when the bacteria enter a cut or abrasion on the skin. After the spore germinates in skin tissues, the bacteria produce a toxin which causes local swelling. The skin infection begins as a raised, itchy bump that resembles an insect bite, but within 1-2 days develops into a vesicle that discharges a clear or cloudy fluid. This is then followed by a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dead) area in the centre. Lymph glands in the nearby area may swell. If cutaneous anthrax is untreated, about 20 per cent of cases will die. Deaths are rare when this form of the disease is treated.
Inhalation anthrax on the other hand, is the most deadly form of anthrax. If inhaled, anthrax spores are deposited in the air sacs of the lungs. About 12 hours after inhalation, initial symptoms begin to appear that may resemble a mild cold or flu. It is estimated that 8,000 to 10,000 spores are needed to cause an infection. Some of the spores are transported to nearby lymph nodes where they germinate. Once germination occurs, disease follows rapidly. The bacteria release toxins leading to haemorrhage, oedema, and death of lung tissue. This stage of the illness lasts from a few hours to a few days. After this, the symptoms may progress to severe breathing problems and shock, followed by cyanosis and a drop in blood pressure. In some cases, brain inflammation develops. Death sometimes occurs within hours.
Anthrax is diagnosed by isolating the organism from the blood, skin lesions, or respiratory secretions or by measuring for specific antibodies in the blood of persons with suspected anthrax. However, it takes some time before the bacillus is isolated, so that persons with symptoms suggestive of anthrax should be treated until the disease is excluded.
With the flu season approaching, it may be difficult to differentiate between the flu and the flu-like symptoms that develop early in inhalation anthrax. However it is important to differentiate between them, as early antibiotic therapy of inhalation anthrax is essential to saving lives. A delay of antibiotic treatment, even for a few hours, can substantially lessen the chances for survival. There are some clues that can help to distinguish one from the other.
One is that anthrax does not cause a stuffy nose as occurs in a common cold. An x-ray of the chest can also provide further evidence for anthrax. When the anthrax spores reach the lymph glands behind the lungs and in front of the spine and germinate, these glands enlarge, producing a characteristic swelling, known as a widened mediastinum, that can be detected on a chest x-ray. In the later stages of inhalation anthrax, fluid accumulates in the pleural covering of the lungs, compressing them, and causing severe respiratory distress. This fluid can sometimes be bloody. The presence of fluid in the pleural space can also be detected on a chest x-ray. While a secondary bacterial pneumonia can occur in influenza, pneumonia is not normally seen in inhalation anthrax.
Gastrointestinal anthrax can develop in people who eat undercooked meat from infected animals with the deposition and subsequent germination of spores in the upper or lower gastrointestinal tract. This form is characterised initially with nausea, loss of appetite, vomiting and fever, progressing rapidly to vomiting of blood, bloody diarrhoea, and abdominal pain. Intestinal anthrax results in death in 25 to 60 per cent of cases.
All three forms of anthrax are treatable with antibiotics, but treatment must begin early. Skin anthrax can be treated with a single antibiotic for as long as 60 days. In treating inhalation anthrax, the Center for Disease Control (CDC) has now recommended a combination of ciprofloxacin or doxycycline, with the addition of one or two of the following antibiotics: ampicillin, chloramphenicol, clarithromycin, clindamycin, penicillin, rifampin and vancomycin. The previous recommendation was for inhalation anthrax to be treated with one antibiotic, but the CDC has made the change because patients who have recently survived inhalation anthrax were treated with combinations of antibiotics.
People who have been exposed to anthrax should get rid of their clothes and shower using soap and a diluted bleach solution as a means of decontamination. Desks can be cleaned with a 5 per cent hypochlorite solution (i.e., standard household bleach). To kill spores, a temperature of 120 degrees centigrade for at least 15 minutes is usually used.
Anthrax can be prevented by the anthrax vaccine which is about 93 per cent effective in protecting against the disease. However, supplies of the vaccine are limited, and it is only earmarked for military use at the present time. It will probably be some time before sufficient supplies become available for civilian use. The vaccine takes at least a month before it offers any protection. Vaccination consists of three shots given two weeks apart followed by three additional shots given at 6, 12 and 18 months. Annual booster shots are necessary to maintain immunity.
A lot of publicity has been given to the stock-piling of antibiotics for the treatment of anthrax. It is not deemed advisable, however, to take antibiotics as a preventive measure. The exceptions, of course, are those at risk of exposure to the anthrax bacteria. There is concern that widespread antibiotic use may cause the anthrax bacillus and other infectious organisms to develop a resistance to these drugs, possibly making the antibiotics ineffective in the future.