Anthrax

Original Editor - Donald John Auson Top Contributors - Donald John Auson, Lucinda hampton and Nupur Smit Shah

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Definition

Anthrax is an acute zoonotic disease caused by the spore-forming bacterium Bacillus anthracis, a microbe that lives in the soil.

• A serious infectious disease caused by gram-positive, rod-shaped bacteria known as Bacillus anthracis.
• Anthrax can be found naturally in soil and commonly affects domestic and wild animals around the world.
• Rare in the United States - people can get sick with anthrax if they come in contact with infected animals or contaminated animal products.
• Contact with anthrax can cause severe illness in both humans and animals.
• Anthrax is not contagious, which means you can’t catch it like the cold or flu.
• Anthrax can occur in four forms: cutaneous, inhalation, gastrointestinal, and inhalation.

Clinically Relevant Anatomy

Anthrax can affect different body systems, depending on the route of infection. It can affect the integumentary system, gastrointestinal/ digestive system and respiratory system.

Etiology

The pathogen that causes Anthrax is a bacterium known as Bacillus anthracis.

Epidemiology

Most cases of anthrax are cutaneous (95%); the remaining cases are inhalation (5%) and gastrointestinal (< 1%). Injection Anthrax have only been reported in Northern Europe.

Incidence of any anthrax infection has been less than 1 case per year in the US for the last 30 years. From 1955–1994, US cases totaled 235, with 224 cases of cutaneous anthrax, 11 cases of inhalation anthrax, and 20 fatalities.

Anthrax is common in Middle East, the Indian subcontinent,  Africa, Asia, and Latin America and is rare in Western Europe. In 1958, approximately 100,000 cases of anthrax occurred worldwide. Anthrax is endemic in Africa and Asia despite vaccination programs.

In 1978, during the Rhodesian civil war, failure of veterinary vaccination programs led to a human epidemic, causing 6500 anthrax cases and 100 fatalities.

In 1982, Thailand had an outbreak of 24 cases, concurrently with 52 cases of cutaneous anthrax after ingestion of contaminated water buffalo meat.

In October 2001, 22 cases of anthrax infection were identified. Most recently in 2016, in Siberia, Russia, there was an outbreak of anthrax that affected at least 13 Siberian people and killed over 2,000 reindeer.

Risk Factors

Occupational hazard for:

• Veterinarians
• Farmers
• Individuals who handle animal wool, hair, hides, or bone meal products.
• Travelers
• Laboratory professionals
• Mail handlers, military personnel, and response workers who may be exposed during a bioterror event involving anthrax spores

There is no racial, sexual, or age predilection for anthrax. However, because anthrax is often related to industrial exposure and farming, the disease most often affects young and middle-aged adults.

Pathophysiology

Anthrax can occur in four different forms, depending on the route of infection.

When the spores get inside the body, from any route mentioned from above, the spores then become anthrax bacteria. Then the bacteria can multiply, spread out in the body, produce toxins (poisons), and cause severe illness.

Clinical Presentation

Clinical manifestations usually happen 1-7 days after exposure from the spores.

Cutaneous Anthrax

Small blisters/ bumps

Swelling

Painless skin sore (ulcer), most often the sore will be on the face, neck, arms, or hands

Gastrointestinal Anthrax

Fever and chills

Swelling of neck and lymph node enlargement

Sore throat

Painful swallowing

Dysphagia

Respiratory distress

Oral bleeding

Hoarseness

Nausea and vomiting or hematemesis

Diarrhea or bloody diarrhea

Headache

Flushing (red face) and red eyes

Stomach pain

Fainting

Swelling of abdomen (stomach)

Inhalation Anthrax

Fever and chills

Chest Discomfort

Shortness of breath

Tachypnea

Cyanosis

Confusion or dizziness

Cough

Nausea, vomiting (hematemesis), or stomach pains

Headache

Diaphoresis

Extreme tiredness

Body aches

Injection Anthrax

Injection anthrax has almost the same manifestation as Cutaneous Anthrax except for it could affect deeper structures and can spread more easily.

Fever and chills

A group of small blisters or bumps that may itch, appearing where the drug was injected

A painless skin sore with a black center that appears after the blisters or bumps

Swelling around the sore

Abscesses deep under the skin or in the muscle where the drug was injected

Diagnosis

Diagnosis is made through history-taking for possible exposure, evaluation of signs and symptoms, diagnostic procedures, and laboratory findings.

The Centers for Disease Control and Prevention (CDC) has resources that can help in diagnosing and investigating anthrax. These are:

Anthrax Case Investigation System

Case Investigation Form

Anthrax Investigation Database

Case Definition

Diagnostic Procedures/ Laboratory Findings

• Gram Staining and Blood Culture
• Enzyme-Linked Immunosorbent Assay (ELISA)
  • ELISA to detect immunoglobulin G (IgG) response to B anthracis protective antigen (PA) is 98.6% sensitive and 80% specific. Protective antigen–competitive inhibition ELISA is used as a second confirmatory step to improve specificity.
• Chest Radiograph
  • widening of the mediastinum,paratracheal and hilar fullness, and pleural effusions
• CT Scan
  • detects hemorrhagic mediastinal and hilar lymph nodes and edema, peribronchial thickening, and pleural effusions
• Lumbar Puncture
  • CSF in patients with anthrax meningitis is grossly hemorrhagic with few polymorphonuclear neutrophils (PMNs) and numerous gram-positive bacilli.
• Histologic Findings

Management / Interventions

The CDC has a set of guidelines for the Prevention and Treatment of Anthrax.

Medical Management

Antibiotics

Antitoxins

Differential Diagnosis

Cutaneous Anthrax

Bubonic Plague

Primary Syphyilis

Gastrointestinal Anthrax

Dysentery

Inhalational Anthrax

Pneumonia (Atypcial or Community- Acquired)

Bacterial Mediastinitis

Other Conditions:

Tularemia

Typhoid

Diphtheria

Psittacosis

Leprosy

Resources

CDC- Anthrax

CDC- Anthrax Bioterrorism

CDC- Anthrax Resources- for additional readings