zoonoses and communicable diseases common to ... - PAHO/WHO

ANTHRAX 21Wood, R.L., R. Harrington, D.R. Hubrich. Serotypes of previously unclassified isolates ofErysipelothrix rhusiopathiae from swine in the United States and Puerto Rico. Am J Vet Res42:1248–1250, 1981.ANTHRAXICD-10 A22.0 cutaneous anthrax; A22.1 pulmonary anthrax;A22.2 gastrointestinal anthraxSynonyms: Malignant pustule, malignant carbuncle, charbon, hematic anthrax,bacterial anthrax, splenic fever, woolsorters’ disease.Etiology: Bacillus anthracis, an aerobic, nonmotile, gram-positive bacillus 3–5microns long that forms centrally located spores. It should be differentiated from B.cereus, which is quite similar. One of the media used to differentiate them is thegamma phage specific for B. anthracis. The etiologic agent is found in a vegetativestate in man and animals. When exposed to oxygen in the air, it forms spores thatare highly resistant to physical and chemical agents.In nature, B. anthracis occurs in a virulent form—the pathogenic agent ofanthrax—and in an avirulent form. Virulence is determined by a capsule that inhibitsphagocytosis and an exotoxin, both of which are plasmid mediated. In turn, the toxinconsists of three protein factors: the protective antigen, the lethal factor, and theedema factor. None of these factors is toxic by itself. When injected intravenouslyat the same time, the protective antigen and the lethal factor are lethal in some animalspecies. The combination of the protective agent and the edema factor producesedema when injected subcutaneously (Little and Knudson, 1986).Geographic Distribution: Worldwide, with areas of enzootic and sporadicoccurrence.Occurrence in Man: The infection in humans is correlated with the incidence ofthe disease in domestic animals. In economically advanced countries, where animalanthrax has been controlled, it occurs only occasionally among humans. Some casesstem from the importation of contaminated animal products. Human anthrax is mostcommon in enzootic areas in developing countries, among people who work withlivestock, eat undercooked meat from infected animals, or work in establishmentswhere wool, goatskins, and pelts are stored and processed. The incidence of humanillness in developing countries is not well known because those sick with the diseasedo not always see a doctor, nor do doctors always report the cases; in addition, thediagnosis often is based only on the clinical syndrome.According to data from recent years, epidemic outbreaks continue to occurdespite the availability of excellent preventive measures for animal anthrax and,therefore, for the occurrence of the disease in humans. There are some hyperendemicareas, as was shown in Haiti when an American woman contracted the infec-