Anthrax

CASES/YEAR
20 (US); 11,000 (Global)
CATEGORY
Zoonoses
AGENT TYPE
Bacteria
OTHER NAMES
Malignant pustule; Malignant edema; Woolsorter disease; Ragpicker disease; Bacillus anthracis infection;
ACUITY
Acute-Severe
INCUBATION
Cutaneous: 1-7 days (as long as 17 days); Gastrointestinal: 1-7 days after ingestion of contaminated meat; [CDC Travel] Inhalation: 1-6 days (range of 1-43 days); [Cecil, p. 83]
INITIAL SYMPTOMS
Cutaneous: A brown-red papule becomes indurated & then ulcerates, producing a black eschar in 2-5 days. Inhalation: Fever, widened mediastinum & bloody pleural effusions; Ingestion: fever, vomiting, abdominal pain, & shock; [Cecil, p. 1887]
PRECAUTIONS
"Contact precautions if uncontained copious drainage. . . . Infected patients do not generally pose a transmission risk." [CDC 2007 Guideline for Isolation Precautions] Person-to-person transmission rarely reported--cutaneous anthrax only; [CCDM, p. 19]
COMMENTS
EPIDEMIOLOGY
Anthrax is rare in North America, but sporadic outbreaks in livestock and wild herbivores are reported every year. Human cases of anthrax have been linked with imported, goat-hide drums. See CDC website for vaccination recommendations and map of endemic areas. [CDC Travel] Following the 2001 anthrax attacks, there were 11 cases of nonfatal cutaneous anthrax and 11 cases of inhalational anthrax (5 fatal). [Harrisons, 18th Ed, p. 193] Reservoirs are mainly herbivores, domestic and wild. Carnivorous animals may become infected after eating infected meat. Biting flies and scavengers feeding on infected carcasses may transmit infection. [CCDM, p. 22-29] Spores are respirable particles; they can survive in the soil for decades. Spores do not form in infected hosts (in vivo), but they are produced in cultures (in vitro) and in infected dead animals in which carcasses have been opened. [PPID, p. 2553] Since 2009, 31 cases of "injectional" anthrax reported in Scotland; [Gorbach, p. 74] Vultures, feeding on infected carcasses, may spread the disease. [ID, p. 1459]

CUTANEOUS ANTHRAX
Cutaneous anthrax may spread to regional lymph nodes and beyond to cause the systemic form of the disease. The case-fatality rate of untreated cutaneous anthrax is 5%-20%. [CCDM, p. 16-17] Cutaneous anthrax begins as a pruritic papule. The skin surrounding the developing ulcer and eschar is edematous. Satellite lesions may appear. Anthrax necrotic ulcers are usually painless compared to painful brown recluse spider bites. [PPID, p. 2554] One of the uncommon causes of nodular lymphangitis; [Am Fam Physician 2001;63:326-32] For a differential diagnosis of cutaneous anthrax, search using the finding, "entry wound with lymph nodes."

INHALATIONAL ANTHRAX
Patients with inhalational anthrax had fever, sweating, nausea/vomiting, nonproductive cough, dyspnea, chest pain, headache, hypoxemia, and elevated hepatic transaminases. The median WBC count was in the high-normal range. Of the 10 patients with chest x-rays, 7 had infiltrates, 7 had mediastinal widening, and 8 had bloody pleural effusions. Blood cultures (taken before antibiotics started) were positive within 24 hours. Postmortem findings included hemorrhagic mediastinitis and hemorrhagic meningitis. Vaccination and antibiotics provide the optimum protection after exposure. [JAMA. 2002;287:2236-52] Case-fatality rate may exceed 85%. [CCDM] CSF findings in hemorrhagic meningoencephalitis include bloody spinal fluid with large gram-positive rods. [PPID, p. 2559] Presentation may be biphasic with 1-3 days of improvement after first phase. X-ray: "Widened mediastinum and pleural effusions are common; infiltrates are rare." [5MCC-2020] The three stages are: 1. Early prodromal (nonspecific findings); 2. Intermediate progressive (mediastinal adenopathy & pleural effusions); and 3. Late fulminant (meningitis, ARDS & shock). Patients in the 2nd stage can still be cured with antibiotics and pleural drainage. [Cecil, p. 1887t]

GASTROINTESTINAL ANTHRAX
Undercooked meat from infected animals can cause gastrointestinal anthrax. Case-fatality rate is about 40%. [CCDM, p. 17] A white pseudomembrane may develop several days after the onset of oropharyngeal anthrax. Patients have fever, dysphagia, and painful swelling of the neck due to cervical adenopathy. Gastrointestinal anthrax occurs rarely--in less than 5% of cases. In the intestinal form, low grade fever is followed by abdominal pain and vomiting. Other possible findings are ascites, hematemesis, and bloody diarrhea. [PPID, p. 2557, 2559] Oropharyngeal anthrax presents with pharyngitis, painful lymphadenopathy, and dysphagia. [Cohen, p. 1125] "Mesenteric adenopathy on CT scan is likely." [5MCC-2020]

INJECTION ANTHRAX
This form is associated with heroin use, and most patients have soft tissue infection accompanied by edema similar to necrotizing fasciitis, cellulitis, or abscess. Case-fatality rate is about 20%. [CCDM, p. 17-18]

RELATED INFECTIONS:
Orf is a viral infection transmitted from infected sheep or goats and occasionally from deer or reindeer. The clinical findings are limited to one or more papules and sometimes regional lymphadenitis. The lesion is described as, ". . . a red to violet vesiculonodule, maculopapule or pustule, progressing to a weeping nodule with central umbilication." Papules may reach 3 cm in diameter and last 3 to 6 weeks. A related condition is milker's nodule caused by a different Parapoxvirus. [CCDM, p. 568] Parapoxviruses infect sheep and goats; the corresponding human infection is called orf. They also infect dairy cattle; the corresponding human infection is called milker's nodes. [PPID, p. 1818-4]
DIAGNOSTIC
Polychrome methylene blue stain (Gram + bacilli in long chains); Culture; PCR; Ag detection; ELISA Ab testing; [CCDM] Confirmed = clinical + pos. culture or 2 other pos. tests (PCR, immunohistochemistry, serology); [ABX Guide: Anthrax - inhalation]
SCOPE
Global; Endemic in certain agricultural areas (sub-Saharan Africa, Asia, South & Central America, southern & eastern Europe); [CCDM]
SIGNS & SYMPTOMS
  • >fatigue, weakness
  • >fever
  • >fever, biphasic or relapsing
  • >myalgia
  • E dysphagia
  • E pharyngitis
  • E stomatitis
  • G abdominal pain
  • G blood in stool
  • G diarrhea
  • G hematemesis
  • G liver function test, abnormal
  • G nausea, vomiting
  • H leukocytosis
  • H lymphadenopathy
  • H splenomegaly
  • N confusion, delirium
  • N headache
  • N seizure
  • N stiff neck
  • R chest pain
  • R cough
  • R dyspnea
  • S entry wound with lymph nodes
  • S lymphangitis
  • S nodular lymphangitis
  • S papules or plaques
  • S pustule
  • S skin blister or vesicles
  • S ulcer of skin
  • X hilar lymphadenopathy
  • X lung infiltrates
  • X pleural effusions
  • *ARDS
  • *bowel obstruction
  • *encephalitis
  • *mediastinitis
  • *meningitis
  • *pericarditis
  • *pulmonary edema
  • *sepsis
  • *shock
  • *stupor, coma
ANTIMICROBIC

Yes

VACCINE

Yes

ENTRY
Inhalation, Ingestion, Needle (Includes Drug Abuse), Scalpel or Transfusion, Skin or Mucous Membranes (Includes Conjunctiva)
SOURCE
Animal Tissue, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated or Infected Meat
RESERVOIR
Birds and Poultry, Cattle, Goats and Sheep, Cats, Deer, Elk and Antelope, Dogs, Horses, Swine, Wild Animals
RISK FACTORS
  • Eat undercooked meat or fish
  • Handle animal carcasses or placentas
  • Handle domestic animals
  • Touch infected farm animals
  • Victim--air release of infectious agents
  • Victim--water/food release
  • Work in a medical or research lab
REFERENCES FOR CASES/YEAR
1. (US) Published in MMWR 2011; 2 or fewer cases per year; Use correction factor of 10 for reported diseases: 10 X 2 = 20;
2. (Global) WHO estimates 2,000 to 20,000 cases/year; [PPID, p. 2551]