Anthrax is a disease that has been known since ancient times, and the organism responsible for anthrax, bacillus anthracis, has been studied for more than a century. The organism can infect the skin, lungs, or GI (gastro-intestinal) tract, resulting in the cutaneous, inhalational, or GI form of the disease respectively. Until the events of September 11th, most cases of anthrax were associated with the agriculture industry, as a result of workers coming into contact with contaminated animal tissue. About 95% of these human anthrax infections were of the cutaneous form. However, it has been known for some time that anthrax could be used to develop a potent biological weapon. In fact, an accident at a biological weapons facility in the Soviet Union in 1979 resulted in 66 deaths from a “weaponized” version of the anthrax organism. Anthrax is now of widespread public and government interest as a result of the 21 cases of bioterrorism related disease that have occurred since September 11th. It is hoped that this article will lead to an increased understanding of the disease, and a greater awareness of the facts and myths surrounding anthrax.
The bacteria that causes anthrax – bacillus anthracis – occurs naturally in soil. The bacteria can form spores, which are very resistant to drought, enabling the organism to survive for decades in the spore state. Disease begins by ingestion, inhalation, or cutaneous inoculation with the spores. Once inside the host, the spores then germinate and become the active bacillus anthracis organism. The bacteria is surrounded by a thick, tough capsule that inhibits the organism’s destruction by the host’s immune system. Once the bacteria enters an active state, it begins to multiply and release toxins that are harmful to the host. These toxins are thought to cause the swelling of tissues known as “edema,” and the destruction of white blood cells. White blood cells contain a variety of proteins that aid in the destruction of bacteria and viruses, but their release into the host in an uncontrolled fashion can cause damage to normal tissue. It is important to note that the deleterious effects of anthrax are predominantly caused by these toxins and not the bacteria itself. This explains why antibiotic treatment is most useful in the early stages of the disease since these drugs act by destroying the bacteria before they can produce these harmful toxins.
Both the cutaneous and inhalational forms of the disease have an incubation period between infection and the onset of symptoms. The incubation period for the cutaneous form is 2-5 days. The skin lesion of anthrax starts out as a blister that enlarges and then ruptures after about a week. A black crust then forms over the lesion. The lesion itself is not dangerous, but the bacillus anthracis bacteria can enter the bloodstream from the lesion and cause more serious forms of the disease. Antibiotic treatment effectively prevents this dissemination but does not eliminate the skin lesion. Diagnosis is relatively easy since the bacteria can be isolated from the lesion or blister fluid and readily identified using a microscope. It should be noted that there are no documented cases of human-to-human transmission of this disease. It is therefore unlikely that anthrax is contagious in humans.
The inhalational form of the disease has an incubation period of 1-6 days. Several thousand spores need to be inhaled to cause disease, and the spores must be rather small to penetrate deep into the lungs. Small spores that can be aerosolized are difficult to manufacture and spore size is the major impediment to making “weapons grade” anthrax. After the spores are inhaled, they are ingested by the white blood cells that live in the lungs and are carried to lymph nodes located between the lungs. Here, the organisms multiply rapidly and begin to produce toxins. The initial symptoms are non-specific such as muscle aches, fever, chills and fatigue. Untreated, the infected individual rapidly develops severe shortness of breath, low blood pressure, and has trouble getting enough oxygen into the bloodstream. The mortality rate for inhalation anthrax is close to 100% in untreated patients. Additionally, people with pre-existing lung disease seem to be at greater risk for the disease than the normal population. Before the bioterrorism cases, it was thought that the inhalational form of anthrax was uniformly fatal even with treatment. However, about 60% of the more recent inhalation anthrax patients have survived due to early recognition and aggressive treatment with antibiotics.
The mainstay of treatment for this disease is antibiotics. Antibiotic prophylaxis for those suspected of being exposed to the bacteria is an area of substantial controversy. Initially, the Centers for Disease Control (CDC) recommended the administration of ciprofloxacin for 4 weeks along with administration of the anthrax vaccine at 0, 2 and 4 weeks post-exposure. Recently, doxycycline has been suggested as an alternative agent, primarily to prevent the development of resistance to ciprofloxacin, but this is contraindicated for pregnant women, and the CDC recommends ciprofloxacin be used in these patients. Amoxicillin has also been suggested as an alternative agent. However there is some concern that bacillus anthracis contains an enzyme that may promote resistance to the penicillins. All of these drugs have side effects, and ciprofloxacin in particular interacts with many other commonly prescribed medications. Determining who should receive prophylaxis remains an area of great controversy. While nasal swabs for the spores do not determine infection, they are useful in determining exposure for epidemiologic purposes. In general, patients with a credible risk of significant exposure should receive prophylaxis.
Many of the anthrax cases have arisen in individuals exposed to spores found in mail. This leads to the question of what steps should be taken in the event a suspicious substance is found in an envelope. First, one should keep others away from the potential threat. The substance and its container should be sealed in a plastic bag if possible to minimize further contamination and to aid in the collection and testing of the material. Activities that may further aerosolize the substance, such as sweeping, are discouraged, since this may further contaminate the area. Emergency medical services (“911”) should be called. All EMS personnel in the United States currently have protocols to handle events of this nature. These personnel also determine if the substance represents a credible exposure. This will determine the treatment and medical follow up of those people who may have been exposed. Most importantly, DO NOT PANIC! If the substance is anthrax, adequate antibiotic prophylaxis will prevent development of the disease. There have been no cases of anthrax in those who have received prophylaxis to date, and clinical studies in animals yield similar results.
In summary, anthrax is a serious but treatable disease. It is not a disease that is contagious, and the only way to develop it is through exposure to the anthrax spores. Those individuals with a credible and significant exposure should receive prophylaxis with an appropriate antibiotic and vaccination, and to date, this has been completely preventative in these patients.
Author: George J. Shaw, MD, PhD, Assistant Professor of Emergency Medicine, Department of Emergency Medicine, University of Cincinnati College of MedicineDr. Shaw is currently an Assistant Professor of Emergency Medicine at the University of Cincinnati College of Medicine in Cincinnati, Ohio. He received his medical degree in 1997 from Georgetown University in Washington, D.C., and completed an internship and residency in Emergency Medicine at University Hospital in Cincinnati. Prior to his medical studies, he received a Ph.D. in Physics at the University of Maryland, College Park.
Disclaimer: Substantial effort has been expended in ensuring the accuracy and timeliness of the material contained in this article, but the writer cannot warrant that the material is accurate and complete in every respect. Use of the material in this article should not replace medical consultation with a personal physician.