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Anthrax



Excerpts have been reprinted with permission from the APHA’s Control of Communicable Diseases Manual (CCDM). Please refer to the CCDM for more complete information.

ANTHRAX ICD-9 022; ICD-10 A22
(Malignant pustule, Malignant oedema, Woolsorter disease, Ragpicker disease)

1. Identification – An acute bacterial disease that usually affects the skin, but may rarely involve the oropharynx, mediastinum or intestinal tract. In cutaneous anthrax, itching of exposed skin surface occurs first, followed by a lesion that becomes papular, then vesicular and in 2-6 days develops into a depressed black eschar. Moderate to severe and very extensive oedema usually surrounds the eschar … Pain is unusual and, if present, is due to oedema or secondary infection. The head, forearms and hands are common sites of infection … Obstructive airway disease due to associated oedema may complicate cutaneous anthrax of the face or neck. Untreated infections may spread to regional lymph nodes and the bloodstream with overwhelming septicaemia. The meninges can become involved. Untreated cutaneous anthrax has a case-fatality rate between 5% and 20%; with effective treatment, few deaths occur. The lesion evolves through typical local changes even after the initiation of antibiotherapy.
 
Initial symptoms of inhalation anthrax are mild and nonspecific and may include fever, malaise and mild cough or chest pain; acute symptoms of respiratory distress, X-ray evidence of mediastinal widening, fever and shock follow in 3-5 days, with death shortly thereafter. Intestinal anthrax is rare and more difficult to recognize; it tends to occur in explosive food poisoning outbreaks where abdominal distress is followed by fever, signs of septicaemia and death in typical cases. An oropharyngeal form of primary disease has been described. 

Laboratory confirmation is through demonstration of the causative organism in blood, lesions or discharges … Rapid identification of the organism through immunodiagnostic testing, ELISA and PCR may be available in certain reference laboratories.

2. Causative agent – Bacillus anthracis, a Gram-positive, encapsulated, spore forming, nonmotile rod (specifically the anthrax spores of B. anthracis are the infectious agent; vegetative B. anthracis rarely establish disease.)

3. Occurrence – Primarily a disease of herbivores; humans and carnivores are incidental hosts. In most industrialized countries, anthrax is an infrequent and sporadic human infection; it is an occupational hazard primarily of workers who process hides, hair (especially from goats), bone and bone products and wool; and of veterinarians and agriculture and wildlife workers who handle infected animals. Human anthrax is endemic in the agricultural regions of the world where anthrax in animals is common, such as Africa and Asia, south and central America, southern and eastern Europe. New areas of infection in livestock may develop through introduction of animal feed containing contaminated bone meal. Environmental events such as floods may provoke epizootics. Anthrax has been deliberately used to cause harm; as such, it could present in epidemiologically unusual circumstances.

4. Reservoir – Animals (normally herbivores, both livestock and wildlife) shed the bacilli in terminal hemorrhages or blood at death. On exposure to the air, vegetative cells sporulate and the B. anthracis spores, which resist adverse environmental conditions and disinfection, may remain viable in contaminated soil for years … Dried or otherwise processed skins and hides of infected animals may harbour spores for years and are the fomites by which the disease is spread worldwide.

5. Mode of transmission – Contact with tissues of animals (cattle, sheep, goats, horses, pigs and others) dying of the disease; possibly also through biting flies … contact with contaminated hair, wool, hides or products made from them … or contact with soil associated with infected animals or with contaminated bone meal used in gardening. Inhalation anthrax results from inhalation of spores in risky industrial processes … Intestinal and oropharyngeal anthrax may arise from ingestion of contaminated undercooked meat … Accidental infections may occur among laboratory workers …

6. Incubation period – From 1 to 7 days, although incubation periods up to 60 days are possible …

7. Period of communicability – Person-to-person transmission is rare. Articles and soil contaminated with spores may remain infective for several years.

8. Susceptibility – There is some evidence of inapparent infection among people in frequent contact with the infectious agent; second attacks can occur, but reports are rare.

9. Methods of control

A. Preventive measures:

1) Immunize high-risk persons with a cell-free vaccine prepared from a culture filtrate       containing the protective antigen … This vaccine is effective in preventing cutaneous and inhalational anthrax: it is recommended for laboratory workers who routinely work with B. anthracis and workers who handle potentially contaminated industrial raw materials … 

2) Educate employees who handle potentially contaminated articles ... 

3) Control dust and properly ventilate work areas in hazardous industries … Maintain continuing medical supervision of employees and provide prompt medical care of all suspicious skin lesions. Workers must wear protective clothing; adequate facilities for washing and changing clothes after work must be provided. Locate eating facilities away from places of work. Vaporized formaldehyde has been used for disinfection of workplaces contaminated with B. anthracis. 

4) Thoroughly wash, disinfect or sterilize hair, wool and bone meal or other feed of animal origin prior to processing.