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DISEASES : Plague
Human plague is caused by infection with the bacillus Yersinia pestis. It is primarily an infection of animals where transmission between animal hosts, such as rats, ground squirrels and cats, occurs via the bite of infected fleas or ingestion of infected animal tissue.
Humans may become infected when they are bitten by rodent fleas which have previously fed on infected hosts. Occasionally, infection may be acquired by direct handling of tissues or fluids of infected animals. In epidemics of the disease human infection can be acquired by the inhalation of infected respiratory secretions from individuals or animals, especially domestic cats, with plague pneumonia.
Symptoms and Signs
Human plague presents in the following ways :
Mode of Transmission
Usually transmitted through the bite of infected fleas (especially from the oriental rat flea). Other sources include the handling of tissues of infected animals, especially rodents and rabbits. Plague may also be transmitted by airborne droplets from patients infected with pneumonic plague. In a bioterrorist setting, plague bacilli would probably be transmitted by infectious aerosol droplets.
This is from 1 to 7 days but maybe a few days longer. For primary plague pneumonia, this is usually 1 to 4 days.
The Ontario Public Health Laboratories will assist in confirmation of suspect cultures for plague, as well as consultation with physicians on suspected cases. Physicians must contact the Central Public Health Laboratory prior to the submission of cultures and/or specimens :
During work hours : 416-235-6100
After-hours Duty Officer : 416-605-3113
Specimens should be handled according to universal precautions and packaged for transport to the Central Public Health Laboratory according to the Transportation of Dangerous Good regulation.
A presumptive diagnosis can be made microscopically by identification of the gram-negative coccobacillus with "safety-pin" bipolar staining in Gram stained smears from a lymph node needle aspirate, sputum, or cerebrospinal fluid sample.
A definitive diagnosis can be made by culturing the organism from blood, sputum, and bubo aspirates.
A four-fold rise in antibody titer in patient serum is also diagnostic.
Streptomycin is the drug of choice. Tetracycline and chloramphenicol may also be used. All are highly effective if used early (within 8 to 18 hours after the onset of pneumonic plague). The patient should be under the care of an infectious disease specialist.
Post-Exposure Prophylaxis for Contacts of Cases
For face to face contacts of patients with pneumonic plague or after a confirmed or suspected bioterrorism attack, the use of doxycycline 100 mg. Orally, twice daily for 7 days or the duration of risk of exposure whichever is longer, is recommended.
Plague 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.
Call the ministry INFOline at 1-800-268-1154
(Toll-free in Ontario only)
In Toronto, call 416-314-5518
Hours of operation : 8:30am - 5:00pm
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