Potential Bioterrorism Agent: Category A
Also known as: Woolsorter Disease
Hospital: Report immediately by phone if bioterrorism suspected, otherwise within 1 day
Lab: Report by phone immediately if bioterrorism suspected, otherwise within 1 day. Send isolates to the State Hygienic Laboratory (SHL) for confirmation
Physician: Report immediately by phone if bioterrorism suspected, otherwise within 1 day
Local Public Health Agency (LPHA): Follow-up required. Iowa Department of Public Health will lead the follow-up investigation.
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Anthrax is a disease caused by the bacterium Bacillus anthracis. It is primarily a disease of wild and domestic animals.
B. Clinical Description
Anthrax is an acute bacterial disease, which usually involves the skin, but may involve the upper throat, lower respiratory tract, chest cavity or intestinal tract. Toxins produced by the bacteria cause the tissue and organ damage associated with anthrax.
In anthrax affecting the skin (cutaneous anthrax), itching of an exposed skin surface occurs first. Itching is followed by a small red lesion that progresses to a blister and, ultimately, a scabbed black ulcer (eschar) with significant surrounding edema. Roughly 5% - 20% of people with untreated cutaneous anthrax die, although prompt treatment with effective antibiotics can substantially reduce the risk of death.
Initial symptoms of anthrax of the lower respiratory tract (inhalation anthrax) are usually mild, resembling an upper respiratory infection. Severe symptoms follow within 3 - 5 days, and include respiratory distress, fever and shock, with death following shortly. X-rays typically show a widened mediastinum. Hemorrhagic mediastinitis and/or meningitis are frequent severe complications. Case-fatality estimates for inhalational anthrax are based on incomplete information, but the rate appears to be extremely high. The case-fatality rate is estimated to be approximately 75%, even with all possible supportive care, including appropriate antibiotics.
Intestinal anthrax is rare and tends to occur in foodborne outbreaks. Fever, vomiting of blood, severe diarrhea, blood infection and death typically follow abdominal pain. Even with treatment, the case-fatality rate for intestinal anthrax can approach 50%.
A form of anthrax affecting the upper throat (oropharyngeal anthrax) has also been described.
Wild and domestic hoofed herbivores (plant-eating animals), including livestock, are the main reservoir for anthrax.. The anthrax bacteria are shed in terminal hemorrhages or blood at death. These spores are very resistant to disinfection and adverse environmental conditions, so they are capable of surviving in soil for decades. Skins and hides of infected animals may harbor the spores for years. Worldwide spread of anthrax occurs primarily through dissemination of contaminated skins and hides.
D. Modes of Transmission
Cutaneous infection occurs through:
- contact with contaminated skins, wool or hides, or products made from these;
- contact with tissues of animals that are clinically ill or dead from anthrax;
- contact with soil contaminated with spores or contaminated bonemeal used in gardening; or, 4) rarely, bites by insects that have bitten infected animals or humans.
Inhalation anthrax may occur in environments where animal hides and wool are processed. It may also occur due to accidental or intentional aerosolization of spores, as may occur with a laboratory accident or bioterrorism event.
Intestinal and oropharyngeal anthrax occurs through ingestion of undercooked contaminated meat.
E. Incubation Period
The incubation period for anthrax is usually 1- 7 days, and most cases occur within 2 days of exposure. However, incubation periods of up to 60 days have been reported.
F. Period of Communicability or Infectious Period
Person-to-person transmission has not been documented with inhalation or intestinal anthrax. Person-to-person transmission with cutaneous anthrax rarely occurs. Products and soil contaminated with spores may remain infectious for decades.
Anthrax is primarily a disease of wild and domestic herbivorous (plant-eating) animals. Unaffected herds of livestock may be exposed through feed containing contaminated bonemeal. Anthrax is an infrequent cause of disease in the United States and a sporadic cause of disease in most industrialized countries. Anthrax in animals is common in Central and South America, southern and Eastern Europe, Africa and Asia. Persons at greatest risk of contracting anthrax are those whose occupations may expose them to contaminated meat, hides or wool. Veterinarians and others who handle and treat infected animals are also at risk. In Iowa, anthrax in animals is reported on rare occasions.
H. Bioterrorism Potential
Category A: Bacillus anthracis is considered a potential bioterrorism agent. If acquired and properly disseminated, Bacillus anthracis could cause serious public health harm and would challenge public health in terms of ability to limit the numbers of casualties.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for anthrax can be found at:
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2000 Red Book: Report of the Committee on Infectious Diseases, 25th Edition. Illinois, American Academy of Pediatrics, 2000.
Heymann, D.., ed., Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
CDC - Anthrax website: emergency.cdc.gov/agent/anthrax/index.asp#