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DISEASES : Anthrax

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. It is primarily a disease of sheep, goats, cattle and swine. Animals shed the bacilli, and on exposure to air, these vegetative forms can form spores which are very resistant in the environment and may remain viable in contaminated soil for many years. Anthrax can also occur in humans when they are exposed to infected animals or tissue from infected animals. In humans the disease usually affects the skin (cutaneous anthrax). It may however infect the nasal passages (inhalation anthrax) and the intestinal tract.

Symptoms and Signs

Cutaneous :
Most (approximately 95%) anthrax infections occur when the bacterium enters a cut or abrasion on the skin. Skin infection begins as a raised itchy bump resembling an insect bite that develops into a vesicle within 1-2 days and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic centre. Lymph glands in the adjacent area may swell. Deaths from cutaneous anthrax infection occur in untreated cases. Therefore, post-exposure prophylaxis with appropriate antibiotics is recommended.

Inhalation : Initial symptoms may resemble a common cold. After several days the symptoms may progress to severe breathing problems and shock. There may be x-ray evidence of mediastinal widening. Post -exposure treatment with appropriate antibiotics should be given as soon as possible. Mortality rates from inhalation of anthrax are high particularly if antibiotics are not instituted soon enough.

Intestinal : This form of anthrax is rare and more difficult to recognize, except that it tends to occur in explosive food poisoning outbreaks. Symptoms include abdominal distress followed by fever, signs of septicemia, and severe diarrhea. Given the difficulty of early diagnosis, this form of anthrax can also lead to death in a number of cases.

Mode of Transmission

Cutaneous anthrax infection is acquired by contact with the tissues of animals dying of the disease, especially the wool, hides or other products made from the animal.

Inhalation anthrax is caused by the inhalation of spores. Contact with the anthrax spores may be through contact with infected animals or transmitted intentionally as an agent of biological warfare. This may also pertain to intestinal anthrax.

Incubation Period

From 1 to 7 days, although incubation periods up to 60 days are possible. Anthrax cannot be transmitted from person to person. Articles and soil contaminated with anthrax spores may remain infective for decades.

Laboratory Diagnosis

The Ontario Public Health Laboratories will assist in confirmation of suspect cultures for anthrax, as well as consultation with physicians on suspect cases. Physicians MUST contact the Central Public Health Laboratory PRIOR to the submission of cultures and/or specimens :

Medical Microbiologist :

After-hours Duty Officer :

Specimens should be submitted to the laboratory that normally provides your bacteriological testing, and should be handled according to universal precautions in a biosafety cabinet in laboratories performing primary isolation and testing of specimens. Physician should contact their microbiology laboratory PRIOR to the submission of any specimens for the diagnosis of anthrax.

Specimens should be handled according to universal precautions and packaged for transport to the Central Public Health Laboratory according to the Transportation of Dangerous Goods regulation.

Appropriate specimens for the diagnosis of anthrax include :

Cutaneous :
Specimens to collect include swab samples of fluid of vesicles or of material beneath the edge of the black scab plus three sets of blood cultures (before administration of antibiotics).

Inhalation :
Sputum samples and three sets of blood cultures should be obtained.

Intestinal :
Gastric aspirates or feces, may be cultured and three sets of blood cultures.


Cutaneous :
Penicillin is the drug of choice for cutaneous anthrax and is given for 5-7 days. Tetracyclines, erythromycin and chloramphenicol are also effective.

Inhalation/Intestinal :
Significant numbers of inhalation anthrax cases in which treatment was begun after patients were significantly symptomatic have been fatal, regardless of treatment. In the absence of information concerning antibiotic sensitivity, treatment should be instituted at the earliest signs of disease with intravenous antibiotic therapy under the care of an infectious disease specialist. Supportive therapy for shock, fluid volume deficit, and adequacy of airway may all be needed.

Post-Exposure Prophylaxis

Confirmed exposure to anthrax is treated with antibiotics and should be started within 24 hours. Treatment with ciprofloxacin, doxycycline or amoxicillin, provides significant protection. Unless anthrax has been confirmed in the area, it is recommended that persons thought to have been exposed await laboratory results prior to being placed on chemoprophylaxis. Caution and physician consultation about individual risk vs. benefit should take place if ciprofloxacin or doxycycline is being considered for pregnant women, and doxycycline for young children.

Should an exposure to anthrax be confirmed, antibiotics should be continued for at least 60 days in all those exposed or longer if indicated.


Anthrax vaccine is not licensed in Canada and would have to be accessed through the Special Access Program at Health Canada which "has a mandate to provide access to non-marketed drugs to practitioners treating patient with serious or life-threatening conditions when conventional therapies have failed, are unsuitable, are unavailable or offer limited options". Health Canada has advised that there is no need to vaccinate members of the general public who have not been exposed to anthrax. If anthrax vaccine is being considered for post-exposure prophylaxis, the responsible physician should immediately consult with the local MOH who in turn will contact the Chief Medical Officer of Health of Ontario (416-314-5487) or his designate.

If the use of anthrax vaccine is being considered, contact should first be made with the local medical officer of health. Following that, the Chief Medical Officer of Health of Ontario or his designate should be contacted at (416) 314-5487 during normal office hours, or through the Spills Action Centre at (416) 325-3000 or 1-800-268-6060, after hours.


Anthrax is a reportable disease in Ontario under the Health Protection and Promotion Act and must be reported immediately to the local medical officer of health by telephone. The disease should be reported even if it is only suspected and has not yet been confirmed.

For more information
Call the ministry INFOline at 1-800-268-1154
(Toll-free in Ontario only)
In Toronto, call 416-314-5518
TTY 1-800-387-5559
Hours of operation : 8:30am - 5:00pm
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