Guides for Emergency Response: Biological Agent or Weapon: Plague
Guides for Emergency Response: Biological Agent or Weapon: Plague AGENT: Plague is a zoonotic (communicable from animals to humans under natural conditions) disease caused by Yersinia pestis. Under normal conditions, humans become infected as a result of contact with rodents, and their fl eas. Th e transmission of gramnegative coccobacillus is by the bite of the infected fl ea, Xenopsylla cheopis, the oriental rat fl ea, or the human fl ea, Pulex irritans. Under normal conditions, three syndromes are recognized: bubonic, primary septicemic, or pneumonic. If a situation develops into a biological warfare or terrorist attack, the plague bacillus would probably be delivered by vectors (fl eas) causing the bubonic variety or, more likely, by aerosol causing the pneumonic type. Bubonic plague is the most common form, and has a secondary formation of large regional lymph nodes called buboes. Blood may clot in the vessels, and may show up in blackened fi ngers and toes. “Natural” plague most oft en is caused by the bite of a fl ea that had dined on infected rodents; a secondary source would be by sputum droplets inhaled from coughing victims. Th ere is a limited incidence of plague in the southwestern desert of the United States. Usually, the rodents die of plague, fl eas feed on the rodents’ bodies, plague multiplies in the fl ea, fl ea becomes unable to bite normally, fl ea gets apprehensive and bites everything, and everything the fl ea bites gets infected with plague. Some U.S. plague victims have been infected by household cats. “Un-natural” plague, the result of terrorist or enemy action, could possibly be an aerosol, or less likely, a release of plaguecarrying fl eas, forms of dissemination that may develop into pneumonic plague leading to quick death. Pneumonic plague is an extremely virulent form, can be transferred from person-to-person, and vaccine seems to have little eff ect on it. During World War II, the Japanese established Unit 731 in Mukden, Manchuria, and carried out experiments in biological warfare on prisoners of war from the United States, Britain, Australia, and New Zealand. Th ey tried aerosolizing plague but were unsuccessful.