NEWS & EVENTS

NEWS ARCHIVE | EDUCATIONAL RESOURCES

ANTHRAX

A number of questions from our clients prompt this brief summary. Please feel free to call or email PRL with further questions.

THE DISEASE(S)

There are three clinical variants of the disease we collectively call "anthrax", which are uncommon in the US. The three clinical variants are: (1) cutaneous (95% of cases), (2) gastrointestinal (rare), and (3), pulmonary (5% or less). Each of the clinical variants is caused by a rod-shaped bacterium called Bacillus anthracis that, when not present in certain types of animals (in the US, mainly livestock and deer), "hibernates" in a special form called a "spore", which is more resistant to the external environment than its parent form. The spores are commonly present in the hair of the above animals and in the dirt surrounding them. The usual type of anthrax seen in the US is the cutaneous form - the spore passes through the skin (cut or insect bite), causes a painless (though may be "itchy"), swollen ulcer to develop. First a vesicle forms, then the roof comes off, revealing a blackish base called an eschar. Once the ulcer has formed the spore may then extend into the lymphatic and blood channels to bring about systemic illness and death in 10-20% of untreated individuals. If the organism is ingested in the meat of an infected animal, it attacks the gastrointestinal tract, causing nausea, vomiting (sometimes bloody), and severe diarrhea. If the patient is untreated, death occurs in 25% to over 50% of cases. The pulmonary form of anthrax is the least common, most deadly, and one of the causative organisms of concern in bioterrorism. In this anthrax variant, the spores are inhaled and begin to grow in the lungs. From the lungs, the organisms are carried into adjacent lymph nodes and through the bloodstream to the entire body. After a few days to a week, flu-like symptoms develop, with increasing difficulty breathing and, without treatment, eventual shock and death in essentially 100% of cases.

In such a bioterrorist attack, the spores would probably be distributed in some manner - air, water, food, etc. It should be remembered that to be effective as a terrorist tool, large amounts of the bacterial material would be needed and, even in the face of a large amount being dispersed, dilution begins instantaneously. Remember also, that we (civilians) are not usually closely packed together, as those in the military often are. Consequently, in civilian populations, as opposed to military populations, the use of these organisms is much more problematic and less effective. Additionally, though these organisms do exist in nature as spores, making them somewhat more resistant to the environment, however they do begin to degrade in sunlight and water (rain).

LABORATORY TESTING

Similar microbiological protocols for specimen collection, handling, transport and laboratory identification are used for suspected cases of anthrax as for other bacterial diseases. For skin lesions, use the sterile swabs brushed vigorously at the base of the lesion and then placed into transport media. If the patient is producing sputum, use the same sputum collection process as you would for any other potential pulmonary infection. Likewise, blood cultures are handled in the same way. It is always advisable to use "universal precautions" when working with or near potentially infectious material of any type - i.e. gloves, lab coat, eye protection. In the case of suspected pulmonary anthrax a gown and mask are advisable. As always it is most helpful if you indicate on the requisition form the working differential diagnosis. Note: Household bleach containing 5.25% hypochlorite, diluted 1:10 in water, is an effective decontaminating solution for working surfaces, instruments and bandages.

SUMMARY

Characteristics of the organism Bacillus anthracis allow it to be used as a bioterrorist tool. However, the vast majority of our exposure to this organism comes from infected animals as described above. Though overwhelming infection with this organism can be lethal in untreated cases, good antibiotic treatment is readily available and, if given soon enough, is quite effective. A vaccine is used for military personnel, who have a much greater likelihood of exposure to the organism as a tool of war. Clinically, as health professionals, we must remain alert for suggestive clinical signs and symptoms, obtain the appropriate samples observing standard protective precautions and promptly make the laboratory determinations. As with other infectious processes, PRL has reporting protocols already in place for notification of appropriate authorities.

Kenneth C. Cummings, MD
Chief, Clinical Pathology
October 8, 2001