Anthrax

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Anthrax facts

  • Anthrax is an infection by bacteria, Bacillus anthracis, usually transmitted from animals.
  • Anthrax causes skin, lung, and bowel disease and can be deadly.
  • Anthrax is diagnosed using bacterial cultures from infected tissues.
  • There are four types of anthrax: cutaneous, inhalation, gastrointestinal, and injection.
  • Anthrax is treated by antibiotics.
  • Pulmonary anthrax is often lethal.
  • It is possible to prevent anthrax.
  • Sadly, the greatest threat of anthrax today is through a bioterrorist attack.
  • Federal, state, and local agencies are working hard to deal with this bioterrorist threat.

What is anthrax? Is anthrax contagious?

Anthrax is a life-threatening infectious disease caused by Bacillus anthracis that normally affects animals, especially ruminants (such as goats, cattle, sheep, and horses). Anthrax can be transmitted to humans by contact with infected animals or their products. In recent years, anthrax has received a great deal of attention as it has become clear that the infection can also be spread by a bioterrorist attack or by biological warfare. Anthrax does not spread from person to person and is not considered contagious.

There have been a number of outbreaks over the years that are usually localized. Most recently in 2016, in Siberia, Russia, there was a major outbreak of anthrax that sickened at least 13 Siberian people and killed over 2,000 reindeer. Authorities believe that the melting permafrost unburied a reindeer that died of anthrax 75 years ago, causing the release of anthrax spores.

What causes anthrax?

The agent of anthrax is a bacterium called Bacillus anthracis. While other investigators discovered the anthrax bacillus, it was a German physician and scientist, Dr. Robert Koch, who proved that the anthrax bacterium was the cause of a disease that affected farm animals in his community. Under the microscope, the bacteria look like large rods. However, in the soil, where they live, anthrax organisms exist in a dormant form called spores. These spores are very hardy and difficult to destroy. The spores have been known to survive in the soil for as long as 48 years. The bacteria secrete toxins composed of three proteins termed protective antigen, lethal factor, and edema factor.

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Learn about the deadliest outbreak of anthrax in recorded history.

Anthrax - From Russia with Love

This article recounts the chilling, yet fascinating story of the deadliest outbreak of anthrax in recorded history. Anthrax is a bacterium (germ) that can cause a serious, sometimes fatal infection. Anthrax can be used as a weapon. In 2001, anthrax was spread through the mail in a powder. Twenty-two people were infected. The events that occurred in Sverdlovsk, Russia, in 1979 demonstrate what can happen when anthrax is released into the air.

How is anthrax contracted?

Anthrax can infect humans in three ways. The most common is infection through the skin, which causes an ugly, dark sore. Humans and animals can ingest anthrax from carcasses of dead animals that have been contaminated with anthrax. Ingestion of anthrax can cause serious, sometimes fatal disease. The most deadly form is inhalation anthrax. If the spores of anthrax are inhaled, they migrate to lymph glands in the chest where they proliferate, spread, and produce toxins that often cause death.

How common is anthrax? What are risk factors for anthrax infection?

Anthrax is now rare in humans in the United States and developed countries. It still occurs today, largely in countries lacking public-health regulations that prevent exposure to infected goats, cattle, sheep, and horses and their products. In the last few years, there have been rare cases of anthrax in people exposed to imported animal hides used to make drums. Drum players, drum makers, and their family members have been infected in this way. The major concern for those of us in western countries (who don't play drums) is the use of anthrax as an agent of biological warfare. Individuals who are at higher risk to become infected with anthrax include

  • veterinarians,
  • livestock producers and farmers,
  • travelers to areas where anthrax is endemic,
  • handlers of animal products (for example, animal hides),
  • laboratory personnel that study anthrax, and
  • mail handlers, military personnel, and individuals trained to respond to bioterrorists and/or biological warfare.

How long is the incubation period with anthrax?

The incubation period (the period between contact with anthrax and the start of symptoms) may be relatively short, from one to five days. Like other infectious diseases, the incubation period for anthrax is quite variable and it may be weeks before an infected individual feels sick.

What kinds of diseases does anthrax cause? What are the signs and symptoms of anthrax infections?

There are four forms of disease caused by anthrax: cutaneous (skin) anthrax, inhalation anthrax, gastrointestinal (bowel) anthrax, and the newly designated injection anthrax.

Cutaneous anthrax

The cutaneous (skin) form of anthrax (80% of all anthrax infections) starts as a red-brown raised spot that enlarges with considerable redness around it, blistering, and hardening. The center of the spot then shows an ulcer crater with blood-tinged drainage and the formation of a black crust called an eschar. There are swollen glands (lymph nodes) in the area. Symptoms include muscle aches and pain, headache, fever, nausea, and vomiting. The illness usually resolves in about six weeks, but deaths may occur if patients do not receive appropriate antibiotics.

Injection anthrax

This new form of anthrax has been identified in heroin-injecting drug users in northern Europe and has not yet been reported in the United States. Symptoms may take days to months before they appear. The signs and symptoms of injection anthrax can include small blisters or bumps that may itch at the injection site, fever and chills, swelling around the sores, and deep abscesses may develop under the skin or muscle. Painless skin sores with black centers (dark scabs) may appear after the blisters or bumps develop.

Inhalation anthrax

The first symptoms are subtle, gradual and flu-like (influenza) with a sore throat and headaches. In a few days, however, the illness worsens and there may be severe respiratory distress with shortness of breath and pain in the chest and/or muscles. Some patients may begin coughing up blood. Shock, coma, and death follow. Inhalation anthrax does not cause a true pneumonia. In fact, the spores get picked in the lungs up by scavenger cells called macrophages. Most of the spores are killed. Unfortunately, some survive and are transported to glands in the chest called lymph nodes. Lymph nodes may swell. In the lymph nodes, the spores that survive multiply, produce deadly toxins, and spread throughout the body. Severe hemorrhage and tissue death (necrosis) occurs in these lymph nodes in the chest. From there, the disease spreads to the adjacent lungs and the rest of the body. Inhalation anthrax is a very serious disease, and unfortunately, most affected individuals will die even if they get appropriate antibiotics. Why is this so? The antibiotics are effective in killing the bacteria, but they do not destroy the deadly toxins that have already been released by the anthrax bacteria.

Gastrointestinal anthrax

Now rare, anthrax of the bowels (gastrointestinal anthrax) is the result of eating undercooked, contaminated meat. The symptoms of this form of anthrax include nausea, loss of appetite, bloody diarrhea and fever followed by abdominal pain. The bacteria invade through the bowel wall. Then the infection spreads throughout the body through the bloodstream (septicemia) with deadly toxicity.

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What specialists treat anthrax?

Although primary-care doctors and pediatricians can treat anthrax, consultation with an infectious-disease specialist is suggested. Other doctors who may help diagnose and/or treat the various types of anthrax include emergency-medicine specialists, pulmonologists, critical-care specialists, and physicians who are experts in treating biologic agents used in warfare.

How is the diagnosis made of anthrax?

The history, including the occupation of the person, is important. The bacteria may be found in cultures or smears in cutaneous (skin) anthrax and in throat swabs and sputum in pulmonary anthrax. Chest X-rays may also show characteristic changes in and between the lungs. Once the anthrax is disseminated, bacteria can be seen in the blood using a microscope. Of course, if anthrax is deliberately spread, the manifestations of the disease may be unusual. Indeed, in the bioterrorism attack in the U.S. in 2001, anthrax spores were spread through the postal system as a white powder mailed with letters.

What is the treatment for anthrax?

In most cases, early treatment can cure anthrax. The cutaneous (skin) form of anthrax can be treated with common antibiotics such as penicillin, tetracycline, erythromycin (Ilotycin, Ery-Ped, Ery-Tab), and ciprofloxacin (Cipro). The pulmonary form of anthrax is a medical emergency. Early and continuous intravenous therapy with antibiotics may be lifesaving. In a bioterrorism attack, individuals exposed to anthrax will be given antibiotics before they become sick. A vaccine exists but is not yet available to the general public. Most experts think that the vaccine will also be given to exposed individuals who are victims of a bioterrorist attack. Of note, anthrax is a reportable disease. That means that local or state health agencies must be notified if a case of anthrax is diagnosed. These agencies can better characterize the anthrax so that the affected individual can receive the most effective treatment for that particular organism.

Individuals exposed to aerosolized spores (bioterrorism scares or attacks, for example) can participate in postexposure prevention of anthrax. Four antibiotics are recommended by the FDA: doxycycline (Doryx, Oracea, Monodox), ciprofloxacin, levofloxacin (Levaquin, Quixin, Iquix), and parenteral procaine penicillin G. In addition to these antibiotics, a three-dose series of anthrax vaccine should be started as soon as possible after exposure.

Is it possible to prevent anthrax? Is there an anthrax vaccine?

Public-health measures to prevent contact with infected animals are invaluable. There is a vaccine available for people at high risk (such as veterinarians, laboratory technicians, employees of textile mills processing imported goat hair, and members of the armed forces). The Department of Defense and the U.S. Centers for Disease Control and Prevention are working very hard to prevent a bioterrorist attack and to be prepared to deal with the consequences if one occurs. For anthrax and other infectious diseases, vaccines with greater efficacy and fewer side effects are under development. Currently, most vaccines are given by injection into fat or muscle below the skin. Early studies in experimental animals are showing promise for an oral vaccine for anthrax. Obviously, a pill is easier to take than a shot, and the pill may even be a safer and more effective route of administration.

What is the prognosis for anthrax infections?

The prognosis for anthrax infections depends on the type of infection and how rapidly antibiotic treatment is initiated. The worst prognosis is for the pulmonary form of anthrax caused by inhaling spores from the environment or from "weaponized" anthrax preparations. The other forms of anthrax have a range of outcomes from good to poor, depending upon how quickly diagnosis and treatment occurs and how severe the infection effects the various organ systems.

REFERENCE:

United States. Centers for Disease Control and Prevention. "Anthrax." Sept. 1, 2015. <http://www.cdc.gov/anthrax/index.html>.

Last Editorial Review: 8/19/2016

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Reviewed on 8/19/2016
References
REFERENCE:

United States. Centers for Disease Control and Prevention. "Anthrax." Sept. 1, 2015. <http://www.cdc.gov/anthrax/index.html>.

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