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 Description of
Agent: Plague is an infectious disease caused by the Gram-negative, bipolar-staining
bacterium, Yersinia pestis. Naturally-occurring plague is most often acquired by the bite
of a flea which had previously fed on infected rodents. In such cases, plague classically
presents as a localized abscess with secondary formation of very large, fluctuant regional
lymph nodes known as buboes (bubonic plague). Plague may also be transmitted via aerosol
and by inhalation of sputum droplets from coughing patients. In such instances, a primary
pneumonic form may develop and, in the absence of prompt therapy, progress rapidly to
death within 2-3 days. Intentional release by belligerents or terrorist groups would
presumably involve aerosolization, but could also involve the release of infected fleas.
Plague may be considered a lethal agent. Signs and Symptoms: Pneumonic plague has an incubation period of 2-3 days, and begins with high fever, chills, headache, hemoptysis, and toxemia, progressing rapidly to dyspnea, stridor, and cyanosis. Death results from respiratory failure, circulatory collapse, and bleeding diatheses. Bubonic plague has an incubation period of 2 to 10 days, and presents with malaise, high fever, and tender lymph nodes (buboes). Bubonic plague may progress spontaneously to the septicemic form, with spread to the CNS, lungs, and elsewhere. Diagnosis: To facilitate prompt therapy, plague must be suspected clinically. A presumptive diagnosis may also be made by Gram or Wayson stain of lymph node aspirates, sputum, or CSF. The plague bacillus may be readily cultured from aspirates of buboes or from the blood of septicemic patients. Treatment: Early administration of antibiotics is quite effective, but must be started within 24 hours of onset of symptoms in pneumonic plague. The treatment of choice is streptomycin (30 mg/kg/day IM in 2 divided doses x 10 days) or gentamicin (2 mg/kg, then 1.0-1.5 mg/kg q 8 hrs x 10 days). Intravenous doxycycline (200 mg, then 100 mg q 12 hrs x 10-14 days) is also effective; chloramphenicol should be added in cases of plague meningitis. Supportive therapy for pneumonic and septicemic forms is typically required. Defense: A licensed, killed vaccine is available. The primary vaccination series consists of a 1.0 ml IM dose initially, followed by 0.2 ml doses at 1-3 months and 3-6 months. Booster doses are given at 6, 12 and 18 months and then every 1-2 years. As this vaccine appears in animal experiments to offer no protection against aerosol exposure, victims of a suspected attack with aerosolized plague, or respiratory contacts of coughing patients, should be given doxycycline (100 mg po bid x 7 days or the duration of exposure, whichever is longer). Decontamination and Isolation: Drainage and secretion precautions should be employed in managing patients with bubonic plague; such precautions should be maintained until the patient has received antibiotic therapy for 48 hours and has demonstrated a favorable response to such therapy. Care must be taken when handling or aspirating buboes to avoid aerosolizing infectious material. Strict isolation is necessary for patients with pneumonic plague. Outbreak Control: In the event of the intentional release of plague into an area, it is possible that local fleas and rodents could become infected, thereby initiating a cycle of enzootic and endemic disease. Such a possibility would appear more likely in the face of a breakdown in public health measures (such as vector and rodent control) which might accompany armed conflict. Care should be taken to rid patients and contacts of fleas utilizing a suitable insecticide; flea and rodent control measures should be instituted in areas where plague cases have been reported. |