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Education and Training

Anthrax


a. Overview
b. Epidemiology
c. Potential as a Biological Weapon/Events that Might Take Place
d. Recognition/Diagnosis
e. Treatment/Environmental Decontamination and Protection

a. Overview:
Anthrax is a bacterial zoonosis1 caused by the spore2 -forming bacteria Bacillus anthracis . There are 3 forms of anthrax: cutaneous, gastrointestinal, and inhalation. Humans acquire unintentional anthrax infections by handling infected animal products such as wool or hides, or by eating undercooked meat or dairy products from infected animals. Anthrax is not contagious, meaning that it is not transmitted from person to person.

Anthrax has been recognized as a disease in animals and in humans for centuries3. Anthrax has been investigated as a potential biological weapon for approximately 80 years.

The cutaneous form of anthrax is the most common form of the disease. Deaths are rare when patients are treated with the appropriate antimicrobial therapy; 80% of untreated cases do not result in death. Gastrointestinal anthrax results in death in 25 to 60% of diagnosed cases. Inhalation anthrax is the most severe form; as many as 75% of treated cases result in death.

The first symptom of cutaneous anthrax is a small sore that develops into a blister, and then into a skin ulcer with a black center. Symptoms of gastrointestinal anthrax include nausea, loss of appetite, abdominal distress, diarrhea, and fever. The initial symptoms of inhalation anthrax are cold or flu-like symptoms including a sore throat, mild fever, and muscle aches. These symptoms are generally followed by chest discomfort, a dry cough, shortness of breath, and fatigue. Unlike the common cold and flu, anthrax symptoms do not include a runny nose. Early identification and treatment are important in all 3 types of anthrax.

b. Epidemiology:
The spores of B anthracis are typically found in soil, are highly resistant to chemical agents and environmental stresses, and can survive in the soil for decades. Spores can be found in soil world wide, but most commonly in agricultural regions in temperate climates. Cattle, goats, sheep, pigs, and horses contract the disease from spores in contaminated soil. In the United States, B anthracis spores are most prevalent in Texas, Oklahoma, parts of the lower Mississippi valley, and in western states4.

The natural reservoirs of the organism are soil and infected animals. Humans can be infected5 by handling contaminated hides, wool, leather, or hair; by ingesting the undercooked meat or dairy products of infected animals; or by inhaling aerosolized spores.

Between 1944 and 2000, 225 cases of cutaneous anthrax were reported in the United States , and 12 cases in 2001 following September 11th . Inhalation anthrax cases in the United States were rare leading up to September 2001, with the last case reported in 1976. Ten cases were reported in late 2001 after the first intentional release of B. anthracis spores in the United States6.

The infective dose of B. anthracis is approximately 8,000-10,000 spores, which equates to 1 deep breath of contaminated air. The disease is not transmitted from person to person7. Communicability is not a concern in managing patients with inhalation anthrax.

c. Potential as a Biological Weapon/Events that Might Take Place:
The Working Group on Civilian Biodefense considers B anthracis to be a potential biological weapon8 for several reasons: causes an acute illness with a high fatality rate; relatively easy to manufacture and develop as a weapon; spores can be stored for long periods without losing infectivity; and the spores can be easily disseminated as an aerosol. The CDC considers B anthracis to be a Category A agent.

The most likely scenario for the intentional use of B anthracis as a biological weapon would more than likely be an aerosol release according to the Working Group on Civilian Biodefense. Such a release in a populated environment would result in large numbers of casualties with a high mortality rate9. A report by the US Congressional Office of Technology Assessment estimated that between 130,000 and 3 million deaths could follow the aerosolized release of 100 kg of anthrax spores upwind of the Washington, DC, are a. The subsequent economical impact of such an incident exceeds $25 billion.

Following an aerosolized release of anthrax spores, exposed individuals would begin to exhibit symptoms within 7 days, although the incubation period can be as long as 6 weeks10. While treatment should begin immediately following an exposure, the impact of a delay in postexposure treatment on mortality rates are not known.

d. Recognition/Diagnosis:
Any first responder or health care worked exposed to acutely ill patients may be the first to recognize the potential threat of an anthrax exposure11. These individuals could include public health officials, police and fire personnel, medical technologists, radiologic technologists, respiratory therapists, nurses, and physicians.

Cutaneous anthrax begins as a small sore that develops into a blister within 1-2 days; the blister further develops into an ulcer with a characteristic black, necrotic center (Figure 1).

Gastrointestinal anthrax initially presents with nausea, loss of appetite, and fever that are followed by abdominal pain, vomiting, and diarrhea.

The initial symptoms of inhalation anthrax can occur within 6-42 days of exposure. The symptoms resemble those of the common cold or flu, and include a sore throat, mild fever, and muscle aches, but without a runny nose. These symptoms are generally followed by chest discomfort, a dry cough, shortness of breath, and fatigue. Shortly thereafter, wheezing, cyanosis, shock, chest wall edema, and meningitis can ensue. Chest x-ray and chest CT show a widened mediastinum, pleural effusions, and/or pulmonary infiltrates (Figure 2). Death can occur rapidly.

Diagnosis of all three forms of anthrax begins by obtaining appropriate exposure history12. Microbiological culture and other types of laboratory procedures are used in definitive diagnosis13,14. Radiographic studies are used in the definitive diagnosis of inhalation anthrax.

e. Treatment/Environmental Decontamination and Protection:
Individuals that are exposed to anthrax and those who have been diagnosed are treated with antibiotics. FDA-approved drugs are ciprofloxacin, doxycycline, and amoxicillin.

The CDC recommends that post-exposure and prophylactic antibiotic treatment continue for 60 days15. Prophylactic treatment is very effective in preventing anthrax following an exposure.

Isolation is not recommended for patients with anthrax.

A vaccine for anthrax has been developed that protects against invasive disease, but it is currently recommended only for high-risk populations such as military, defense, and biomedical research personnel.

Laboratory specimens should be handled using Biosafety Level 3 protocol and precautions16.

Decontamination of an area or environment17 contaminated with anthrax spores can be a difficult proposition, depending upon the circumstances of the release.

Overview of Anthrax:
 

Incubation Period (days) Clinical Features
1. Cutaneous
2. Gastrointenstinal
3. Inhalation
Infection Control
1-42 days 1. Cutaneous lesion with black center
2. Nausea, fever, abdominal pain, vomiting, diahrea.
3. Sore throat, fever, muscle aches, chest discomfort, a dry cough, shortness of breath, fatigue.
Standard precautions. No person to person spread by air.
Laboratory: BSL-3 environment


 

Laboratory Samples Adult Treatment Prophylaxis
Cutaneous ulcer swab, blood cultures, pharyngeal swab, stool, sputum, CSF. Antibiotic therapy. Ciprofloxacin, doxycycline, amoxicillin.
Duration: 60 days
Ciprofloxacin and Doxycycline
Duration: 60 days


References:
Anthrax. Disease Fact Sheet. Ohio Dept. of Health http://www.odh.ohio.gov/ASSETS/D4144989BB0049D58305183A4F9655D7/forfs.PDF

Epidemiology of Anthrax. World Wide Health Organization http://www.who.int/topics/anthrax/en/

Emergency preparedness and response: Anthrax, CDC, http://www.bt.cdc.gov/agent/anthrax/

Bioterrorism alleging use of anthrax and interim guidelines for management-United States. CDC, MMWR, 48(4):69-74. 1999

Carroll K, Held M, Stombler R, Bryan J. Laboratory preparedness for bioterrorism: from the phlebotomist to the pathologist. Laboratory Medicine 24(3):169-182, March 2003.

Cieslak TJ, Eitzen EM. Clinical and Epidemiological principles of anthrax. Emerging and Infectious Diseases 5(4):552-555. 1999

Inglesby TV, Henderson DA, et al. Anthrax as a Biological Weapon. JAMA 281(18):1735-1745, May 12, 1999.

Jernigan JA, Stephens DS, et al. Bioterrorism-Related Inhalational Anthrax: The First 10 Cases Reported in the United States. Emerging and Infectious Diseases 7(6):933-44. 2001

Notes:
1Zoonosis : a disease that can be acquired by humans from an animal source.

2A bacterial spore is a dormant form of the bacteria that, under appropriate conditions, can cause the disease.

3Anthrax is known to have caused disease as long ago as 1500 BC when it is thought to have caused the Fifth Egyptian Plague. An anthrax outbreak in Iran in 1945 killed 1 million sheep. Anthrax was first developed as a potential biological warfare agent by Germany in WW I.

4 The highest number of reported cases are in the western states.

5 Laboratory workers are at particular risk for anthrax infection due to potential exposure to aerosols and open culture plates and the potential for needle injuries.

6 A total of 23 confirmed cases of bioterrorism-related anthrax (10 inhalation, 13 cutaneous) occurred in the United States In the anthrax attacks following September 11th.

7 There are no known cases of person-to-person transmission. Isolation is an appropriate precaution until there is laboratory confirmation of the disease.

8Germany first developed anthrax as a potential biological weapon in 1915. The US began to develop anthrax weapons in 1943. In the 1970's, the US ceased the development of biological weapons, although defense research continues today.

9The accidental release of anthrax spores at a military facility in the Soviet Union in 1979 resulted in 79 anthrax cases with 68 deaths.

10The incubation period for the disease is 1 to 42 days.

11The initial symptoms of anthrax will vary depending upon the type of exposure.

Figure 1

Cutaneous anthrax lesion with black center . (http://www.bt.cdc.gov/agent/anthrax/anthrax-images/cutaneous.asp)

Figure 2

Chest X-ray showing prominent superior mediastinum and possible small left pleural effusion.

12The exposure type will dictate the form of the initial symptoms.

13The organism can be successfully isolated using routine laboratory procedures.

14Laboratory workers are at high risk of infection and Biosafety Level 3 precautions must be used.

15Anthrax spores may require an extended period of time to become infective in a host.

16Information on BSL precautions can be found on the following site: (http://www.cdc.gov/od/ohs/biosfty/bmbl4/bmbl4s2.htm)

17Details on environmental decontamination and infection control can be found at the following site: (http://jama.ama-assn.org/cgi/content/full/281/18/1735)