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

26 BACTERIOSESpened in the 1974 epizootic in Texas (USA), during which 218 cattle, 6 horses, and1 mule died. Eighty-three percent of the fields where the outbreak took place hadacid pH soil and 94% had subsoil with an alkaline pH (Whitford, 1979).Contaminated animal by-products, especially bone meal and blood meal used asfood supplements, can also give rise to distant foci of infection.Another mode of transmission is cutaneous entry through insect bites, but this isconsidered of minor epidemiologic importance.Role of Animals in the Epidemiology of the Disease: Animals are essential.Anthrax is transmitted to humans by animals or animal products. Transmissionbetween humans is exceptional.Diagnosis: The presence of the etiologic agent must be confirmed by microscopicexamination of stained smears of vesicular fluid (in man), edemas (in swine), andblood (in other animals); by culturing the microorganism from the liquid aspiratedfrom malignant pustules or from blood samples of a dead or dying animal; and byinoculation of laboratory animals (guinea pigs and mice). If the material is contaminated,cutaneous inoculation (by scarification) should be used. The use of antibioticsquickly reduces the possibility of isolating the etiologic agent.The fluorescent antibody technique applied to fresh stains or blood smears canprove useful for presumptive diagnosis. Smears of blood or other bodily fluids canalso be stained using the Giemsa or Wright method to make the pink capsule thatsurrounds the bacillus stand out. The Ascoli precipitation test has limited value dueto its limited specificity, but is still used in some laboratories for animal products,from which the agent cannot be isolated.The ELISA and Western Blot tests can be used to detect antibodies to the protectiveantigen in individuals who have had anthrax and from whom the agent cannotbe isolated, i.e., in retrospective studies (Thurnbull et al., 1986; Sirisanthana et al.,1988; Harrison et al., 1989). Antibodies have also been found in people living nearanimal reserves in Africa who have been exposed to anthrax in wild animals withoutbecoming ill themselves (Thurnbull et al., 1991).Control: In man, the prevention of anthrax is based mainly on: (a) control of theinfection in animals; (b) prevention of contact with infected animals and contaminatedanimal products; (c) environmental and personal hygiene in places whereproducts of animal origin are handled (adequate ventilation and work clothing); (d)medical care for cutaneous lesions; and (e) disinfection of fur and wool with hotformaldehyde. Occupational groups at risk may benefit from vaccination with theprotective antigen.The human vaccine used in the US and Great Britain is acellular and consists ofa filtrate of B. anthracis culture from a nonencapsulated strain that is adsorbed withaluminum hydroxide. This vaccine is not very potent and may not protect against allfield strains. In the countries of Eastern Europe and in China, a live attenuated sporevaccine is administered by scarification.In animals, anthrax control is based on systematic vaccination in enzootic areas.Sterne’s avirulent spore vaccine is indicated because of its effectiveness and safety.The vaccine consists of spores from the nonencapsulated 34F2 strain with an adjuvant—usuallya saponin—and is currently used worldwide, with a few exceptions.It is suitable for all domestic animal species. However, goats sometimes have severe