Anthrax

Submitted by John N. Goldman, M.D., chief, division of Infectious Diseases, Penn State Hershey Medical Center
What is it?
Anthrax is a disease caused by Bacillus anthracis, bacteria that lives in the soil. Animals such as cattle, sheep and goats are the usual hosts for anthrax and contact with infected animals or animal products infect humans secondarily. It can infect the skin, lungs, and gastrointestinal tract. In the year 2001, terrorists spread anthrax by sending spores through the mail in the United States. A spore is a dormant (inactive) form of bacteria that can survive under poor conditions, such as high temperatures and dryness. When the conditions are right, these spores can then become active again.
Who gets it?
Outbreaks of anthrax among cattle or people are rare in the United States because most animals are vaccinated against the disease. It occurs most often in agricultural regions outside the United States, such as the Caribbean, southern and eastern Europe, South and Central America, Asia, Africa, and the Middle East. People who handle the contaminated animals, such as farmers, veterinarians, or butchers, are more likely to get the disease. However, anthrax spores can be grown in a laboratory, and we have seen that people can contract anthrax when it is used as a weapon in biological warfare.
What are the forms of anthrax and what are the symptoms of each form?
There are three forms of anthrax in humans:
Cutaneous – or skin anthrax
Pulmonary – or inhalation anthrax
Gastrointestinal – or ingested anthrax
The cutaneous, or skin, anthrax results from spores getting on the skin and then getting into a break in the skin. There is a 1-7 day incubation period. In this environment, the spores begin to grow and cause a small raised area – known as a papule – a person may have localized itching that may then form a small blister that then develops into an ulcerated area that becomes covered with a black scab – or eschar in about 2-6 days. The area is commonly seen on the head, forearm and hands. There may be fever, local redness and swollen lymph glands in the area. Even if untreated, skin anthrax has a relatively low mortality and, if treated with antibiotics, is rarely ever fatal. This is the most common form of anthrax.
Pulmonary, or inhalation, anthrax results from inhalation of the spores into the lungs. The incubation period can be from 2-60 days for the symptoms to occur. The spores then grow and get into the local lymph nodes and lymphatic vessels and cause an aggressive inflammation in the tissues of the chest – known as the mediastinum. There may be hemorrhage locally as well as spread of the bacteria to the brain resulting in meningitis in as many as 50% of affected individuals. The earliest symptoms of pulmonary, or inhalation, anthrax are very nonspecific and may resemble the early phases of the flu – with fever, muscle aches and pains, and mild respiratory complaints. If untreated and these symptoms progress, it may lead to death. Pulmonary anthrax has been quite rare in this country with only 18 cases reported prior to the events of September 11th.
The gastrointestinal form of anthrax results from eating meat from infected animals. The incubation period is typcially 1-7 days and includes symptoms such as abdominal pain, nausea, vomiting and fever following ingestion of contaminated food or water bloody diarrhea, and vomiting blood. This results in infected areas of the intestines with death of tissues and is almost always fatal. Gastrointestinal anthrax has never been seen in this country.
Is anthrax contagious?
Anthrax is not contagious, that is, it cannot be spread from person to person. The reason it cannot be spread is because infected persons have only the actively growing bacteria and do not have the infectious spores.
How many spores does it take to get infected?
The best evidence on this suggests that it takes between 8,000 and 40,000 spores to be inhaled, perhaps fewer to cause the cutaneous form of anthrax. One would guess that it takes many more organisms to cause the gastrointestinal form, since it is so rare and since infected meat may contain millions of organisms.
What is the difference between “exposed to” and “infected with” anthrax?
One can be exposed to anthrax without getting infected with the bacteria, and, in fact, this is probably the most common occurrence. One becomes infected only when the spores grow successfully and multiply in tissues. The spores may not grow or the body’s natural defenses may kill the bacteria before they cause disease. Having the spores recovered from the nose or skin indicates exposure only – but unless the bacteria successfully grow in the skin, lungs or gastrointestinal tract, there is no infection.
How is it diagnosed?
To diagnose anthrax, your doctor will evaluate your symptoms, taking into consideration any possibility that you could have had contact with the Bacillus anthracis bacterium. He or she may take samples of any skin infections, or respiratory secretions, called sputum. However, there are no tests that can be used to reliably detect the presence of anthrax in exposed persons. This is because the bacteria are present in only small numbers on the skin or on mucous membranes of the nose or pharynx before an infection is established. Without the locus of infection on the skin or in the lungs, the usual tests are just not sensitive enough to find the organism in a high percentage of those exposed. Some of these tests are used for epidemiological studies to see if any persons within a group that may have been exposed are positive. If any are positive, then one may consider that all of those exposed have been put at risk and treatment of the entire group with prophylactic antibiotics may be considered.
How quickly must a possible exposure be treated?
The usual incubation period of anthrax is from several days to as many as 60 days from a single discrete exposure. This gives several days to assess the risks involved. Assessment by a physician or other person knowledgeable in this area should be undertaken sooner rather than later. No preventative measure needs to be given in these first few days, even for true exposure. This is especially true since all antibiotics, as well as other drugs, have the potential to cause serious side effects in some people.
What is the treatment ?
While anthrax usually kills infected animals, it can be successfully treated in humans if caught in the early stages. Penicillin has been the drug of choice for years and remains effective, even for the infections we have all read about recently. Other drugs from the penicillin family such as amoxicillin should be equally effective. Doxycycline, one of the tetracycline family of antibiotics – and most recently listed as the CDC’s drug of choice in treating anthrax, is also effective. Ciprofloxacin – more commonly known as Cipro – is one of the quinolone antibiotics and is also effective. Cipro has made news since the September 11th terrorist attack and is recommended as the first drug to use until the sensitivities of the organisms are known because the Soviet Union was known to produce anthrax bacilli that were resistant to penicillin and tetracycline in their germ warfare program. The anthrax used in the most recent incidents, however, has all been sensitive to all antibiotics listed above. Lung infections may be treated with intravenous antibiotics. It is important to take the full course of prescribed antibiotics to prevent complications. If untreated, cutaneous anthrax may result in death. Untreated inhalation anthrax always results in death.
According to the American Medical Association and other authorities, physicians should not prescribe antibiotics for patients as a preventive measure against anthrax. This may lead patients to initiate unnecessary treatment and could contribute to the development of antibiotic resistant organisms.
Is there an anthrax vaccine?
The vaccine is a cell-free filtrate vaccine, which means it contains no dead or live bacteria in the preparation. Anthrax vaccines intended for animals should not be used on humans. The vaccine is reported to be 93 percent effective in protecting against anthrax and is not recommended for the general public.
Self-care tips
People who work in professions that involve frequent contact with animals or animal products that could be infected with anthrax can get an anthrax vaccine that is highly effective against the disease. People who will be visiting countries where there is poor control of the disease should not eat meat that has not been properly prepared or cooked, and should avoid contact with animals or animal products that could be contaminated.