Anthrax

Anthrax: Excerpt from The 5-Minute Pediatric Consult

Andrew P. Steenhoff, MD

Anthrax - BASICS

Anthrax - description

Bacillus anthracis is a spore-forming, Gram-positive rod that can cause acute infection (anthrax) in humans and animals.

Anthrax - general prevention

• Antibiotics are effective against germinating Bacillus anthracis but not against the spores. Therefore, if prophylactic antibiotics are stopped prematurely, remaining spores can cause disease when they germinate. This phenomenon of delayed-onset disease does not occur with cutaneous or gastrointestinal exposures.
• Where the threat of transmission of Bacillus anthracis spores is deemed credible, decontamination of skin and potential fomites (e.g., clothing) may be considered to reduce the risk for cutaneous and gastrointestinal forms of the disease.
• Anthrax vaccine absorbed (AVA) is the only licensed human anthrax vaccine in the US. Primary vaccination consists of subcutaneous injections at 0, 2, and 4 weeks, and three booster vaccinations at 6, 12, and 18 months. Annual booster injections are required to maintain immunity. Most common adverse event is injection-site discomfort (e.g., edema, pain, local hypersensitivity).

Pulmonary disease caused by anthrax is a hemorrhagic mediastinitis with pleural effusions and not a bronchopneumonia.

Anthrax - epidemiology

Anthrax - incidence

• Anthrax is primarily zoonotic. Most naturally acquired anthrax infections are cutaneous (95%). Inhalational (5%) and GI (<1%) forms are particularly rare.
• Prior to October 2001, only 18 cases of inhalational anthrax were reported in the US during the 20th century.
• No human-to-human spread of inhalational anthrax has been reported.
• Rare cases of human-to-human transmission of cutaneous anthrax have been reported after direct contact with infected skin lesions.
• Anthrax has been used as an agent of bioterrorism.

Anthrax - pathophysiology

• After inhalation, wound inoculation, or ingestion, Bacillus anthracis spores infect macrophages, germinate, and proliferate.
  • Proliferation occurs at the site of infection and in regional lymph nodes.
  • Replicating bacteria release toxins, leading to edema, hemorrhage, and necrosis.
• Incubation period depends on the route of transmission.
  • Inhalational anthrax: Infection requires inhalation of >8,000 spores; incubation period is 2–60 days.
  • Cutaneous anthrax: Spores enter a cut or abrasion in the skin; incubation period is 1–12 days.
  • Gastrointestinal anthrax: Spores are ingested in undercooked, infected meat; incubation period is 1–7 days; infection occurs in the upper (oropharyngeal lesions) or lower (intestinal lesions) GI tract.
• Hematogenous spread of the bacteria causes infection at other sites, including the CNS, liver, spleen, and kidney.

Anthrax - associated conditions

If anthrax is intentionally released, physicians must be alert for diseases caused by other potential biologic warfare agents (e.g., plague, tularemia, Q fever, smallpox, and botulism).

Anthrax - DIAGNOSIS

Anthrax - signs & symptoms

Anthrax - history

• Inhalational anthrax:
  • Clinical presentation is a 2-stage illness.
  • Initial symptoms are nonspecific and last 1–3 days. They include low-grade fever, dry cough, headache, vomiting, chills, weakness, abdominal pain, and substernal discomfort. This stage may be followed by a brief period of apparent recovery.
  • 2nd-stage symptoms develop abruptly 2–5 days later: fever, hemoptysis, dyspnea, chest pain, and profuse diaphoresis. Death may occur within 1–2 days.
• Cutaneous anthrax:
  • Painless lesions develop on affected areas soon after exposure.
  • Systemic symptoms of fever, malaise, and headache may occur.
• GI anthrax:
  • Oropharyngeal form causes sore throat, dysphagia, and fever.
  • Intestinal form also causes nausea, vomiting, anorexia, severe abdominal pain, and bloody diarrhea.

Anthrax - physical exam

• Inhalational anthrax:
  • Tachypnea, hypoxia, cyanosis
  • Stridor, rales, signs of pleural effusion
  • Hemoptysis, hematemesis, melena
• Cutaneous anthrax:
  • Initial painless, pruritic macule or papule enlarges into a 1–3-cm round ulcer by the second day.
  • 1–3-mm vesicles with clear or serosanguineous fluid surround the ulcer.
  • A painless, depressed, black eschar follows, often with extensive local edema.
  • Over 1–2 weeks, the eschar dries, loosens, and falls off, occasionally with scarring.
  • Painful, regional lymphadenopathy may occur.
• GI anthrax:
  • Unilateral oral or esophageal ulcers, cervical lymphadenopathy
  • Cecal or terminal ileal ulcers (Intestinal anthrax progresses to massive ascites and acute abdomen.)
• Disseminated anthrax (potential complication of any of the above forms of anthrax):
  • Sepsis syndrome: Tachycardia, hypotension, septic shock
  • Meningitis: Meningismus, delirium, obtundation

Anthrax - tests

Anthrax - lab

• Gram-stain smear and culture from vesicular fluid:
  • Diagnose cutaneous anthrax
  • Gram stain reveals large, Gram-positive, boxcar-shaped bacilli.
  • Capsule is visible on polychrome methylene blue stain.
  • Bacillus anthracis grows readily on blood agar.
• Anthraxin skin test:
  • Measures anthrax cell-mediated immunity
  • It is positive in 80% of patients within 72 hours of infection and in >95% of cases within 3 weeks.
  • The test was positive in 72% of patients >16 years after recovery.
• Serologic enzyme-linked immunosorbent assay (ELISA):
  • Measures antibodies to the lethal and edema toxins of Bacillus anthracis
  • Positive if a single acute-phase titer is >1:32 or if there is a fourfold or greater rise between acute and convalescent titers collected 4 weeks apart
• Polymerase chain reaction, immunohistochemical staining
• Nasopharyngeal swab or induced respiratory secretion culture:
  • Used for epidemiologic investigation
  • The sensitivity, specificity, and predictive value of nasal swab testing are unknown; therefore, this test should not be used to guide the use of postexposure prophylactic antibiotics.
• Blood culture: Patients with cutaneous anthrax may have bacteremia with Bacillus anthracis even without significant signs of systemic disease.
• CBC
• Serum electrolytes, glucose, and calcium:
  • Hypokalemia, acidosis, hypoglycemia, and hypocalcemia occurred during experimental anthrax infection in animals.
  • Hemorrhagic meningitis

Anthrax - imaging

Chest x-ray (or chest CT scan):

• Inhalational anthrax causes a hemorrhagic mediastinitis.
• X-ray shows a widened mediastinum and pleural effusions.
• No infiltrates are present.

Anthrax - differencial diagnosis

• The prodromal illness of inhalational anthrax may resemble a lower respiratory tract infection, although upper respiratory infection symptoms are characteristically absent.
• Patients with inhalational anthrax may have a widened mediastinum on chest radiograph which may resemble an aortic aneurysm or bacterial mediastinitis.
• Necrotic skin lesions may resemble plague, tularemia, ecthyma gangrenosum, and brown recluse spider bite.
• Gastrointestinal anthrax may be confused with other infectious causes of enteritis (e.g., Shigella, Salmonella, Yersinia, Campylobacter, enterohemorrhagic Escherichia coli, Clostridium difficile, colitis), intussusception, Meckel diverticulum, and inflammatory bowel disease.

Anthrax - TREATMENT

Anthrax - general measures

Direct physical contact with a substance alleged to be anthrax:

• Wash exposed skin and articles of clothing with soap and water.
• Administer postexposure prophylaxis until the substance is proved not to be anthrax.
• Contact the public health department or the Centers for Disease Control and Prevention (CDC).

Anthrax - medication

• Postexposure prophylaxis:
  • Ciprofloxacin 15 mg/kg (up to 500 mg) or doxycycline 2 mg/kg (up to 100 mg) PO b.i.d. for 60 days. (Pediatric: Use ciprofloxacin for initial prophylaxis. Switch to amoxicillin or penicillin if susceptibility testing permits.)
• Treatment:
  • For all forms of anthrax, begin with IV therapy and switch to oral therapy when clinically appropriate. Treat for 60 days (IV and PO combined).
  • Inhalational or gastrointestinal anthrax: Ciprofloxacin 15 mg/kg (up to 400 mg) or doxycycline 2 mg/kg (up to 100 mg) IV q12h plus clindamycin or rifampin
  • Cutaneous anthrax: Ciprofloxacin or doxycycline IV. (Pediatric: Begin therapy with ciprofloxacin [plus clindamycin or rifampin for inhalational/gastrointestinal anthrax] and convert to penicillin G IV if susceptibility testing permits and when clinical improvement is documented.)

Anthrax - FOLLOW UP

Anthrax - prognosis

• Inhalational anthrax:
  • Case fatality rates were previously estimated to be >85% after symptoms develop. However, early use of appropriate antibiotic therapy appears to improve survival.
  • Survival rate is higher if symptoms develop >30 days after exposure.
• Cutaneous anthrax
  • Case fatality rate is 20% without antibiotic treatment and <1% with antibiotic treatment.
• Gastrointestinal anthrax: Case fatality rate is 25–60%.

Anthrax - complications

• Antibiotic therapy of cutaneous anthrax limits the likelihood of developing systemic symptoms but does not change the course of the eschar formation.
• Systemic dissemination of inhalational, cutaneous, or gastrointestinal anthrax may lead to sepsis, meningitis, and death.

Anthrax - bibliography

1. Centers for Disease Control. Update: investigation of bioterrorism-related anthrax and interim guidelines for exposure management and antimicrobial therapy, October 2001. MMWR Morb Mortal Wkly Rep. 2001;50(42):909–919. Erratum in: MMWR Morb Mortal Wkly Rep. 2001;50(43):962.
2. Centers for Disease Control. Use of anthrax vaccine in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep. 2000;49(RR-15):1–20.
3. Kyriacou DN, Adamski A, Khardori N. Anthrax: From antiquity and obscurity to a front-runner in bioterrorism. Infect Dis N Am. 2006;20:227–251.
4. Scorpio A, Blank TE, Day WA, et al. Anthrax vaccines: Pasteur to the present. Cell Mol Life Sci. 2006;63:2237–2248.
5. Stocker JT. Clinical and pathologic differential diagnosis of selected potential bioterrorism agents of interest to pediatric health care providers. Clin Lab Med. 2006;26:329–344.

Anthrax - MISCELLANEOUS

Infection control:

• Immediately notify the hospital epidemiologist, infection control department, or local health department of suspected cases.
• No data suggest that patient-to-patient transmission of inhalational anthrax occurs. Standard barrier isolation precautions are recommended for all hospitalized patients with all forms of anthrax infection. High-efficiency particulate air filter masks or other measures for airborne precautions are not indicated.
• There is no need to immunize or provide prophylaxis to patient contacts unless they, like the patient, were exposed to the aerosol.
• If anthrax is used as a bioweapon, spores may be detected on environmental surfaces. Inhalational anthrax is unlikely to be caused by secondary aerosolization of these spores.

Anthrax - CODES

Anthrax - icd9

022.9 Anthrax, unspecified

022.0 Cutaneous anthrax

022.1 Pulmonary anthrax

Anthrax - FAQ

• Q: Does the government have a plan in place if there were mass exposure to anthrax?
• A: Yes. Under emergency plans, the federal government would ship appropriate antibiotics from its stockpile to wherever they are needed.
• Q: Should individuals ask their physicians to write a prescription for ciprofloxacin (or other antibiotic) so they have prophylaxis available?
• A: No. Ciprofloxacin and other antibiotics should not be prescribed unless there is a clearly indicated need. Additionally, indiscriminate prescribing and widespread use of ciprofloxacin could hasten the development of drug-resistant organisms.
• Q: Can a person get screened or tested for anthrax?
• A: No screening test is available to determine whether anthrax exposure has occurred. The only way exposure can be determined is through a public health investigation.
• Q: What are the clues to differentiate pulmonary or inhalational anthrax from RSV in children?
• A: Children with pulmonary anthrax display a high WCC with left shift compared to the relatively normal WCC of those with RSV. Blood O2 levels may be severely depressed in inhalational anthrax.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Gastrointestinal Anthrax

• Back to disease: Gastrointestinal Anthrax: Introduction
• Next Book Extract About Gastrointestinal Anthrax: Surveys relating to Gastrointestinal Anthrax
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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