Agents Anthrax Access Pid Help |
 Description
of Agent: Anthrax is a highly lethal infection caused by infection with the
gram-positive bacterium, Bacillus anthracis. In naturally-acquired cases, organisms
usually gain entrance through skin wounds (causing a localized infection), but may be
inhaled or ingested. Intentional release by belligerents or terrorist groups would
presumably involve the aerosol route, as the spore form of the bacillus is quite stable
and possesses characteristics ideal for generation by aerosols. Signs and Symptoms: The incubation period for inhalation of anthrax is 1-6 days. Fever, malaise, fatigue, cough, and mild chest discomfort are rapidly followed by severe respiratory distress with dyspnea, diaphoresis, stridor, and cyanosis. Shock and death occur within 24-36 hours of the onset of severe symptoms. In cases of cutaneous anthrax, a papule develops, then vesicates, finally developing into a black eschar surrounded by moderate to severe edema. The lesions are usually painless. Without treatment, the disease may progress to septicemia and death, with a case-fatality rate of 20%. With treatment, fatalities are rare. Diagnosis: Physical findings are typically non-specific in inhalational cases, with initial complaints of malaise, fever, headache, and possibly substernal chest pain. A widened mediastinum is sometimes seen on x-ray late in the course of illness, and correlates with a pathologic finding of hemorrhagic mediastinitis, the "classic" presentation of inhalational anthrax. The bacterium may be detected by Gram stain of blood and by blood culture late in the course of illness. Treatment: Although usually ineffective in inhalational cases, once symptoms are present, antibiotic treatment with high-dose penicillin, ciprofloxacin, or doxycycline should nonetheless be administered. Although typically sensitive to penicillin, resistant isolates are readily produced in the laboratory. For this reason, in the case of an intentional release, and in the absence of antibiotic sensitivity data, treatment should be initiated with IV ciprofloxacin (400 mg q 8-12 hrs) or IV doxycycline (200 mg initially, followed by 100 mg q 12 hrs). Supportive therapy may be necessary. Defense: A licensed vaccine is available for those at risk of exposure. Vaccination is undertaken at 0, 2, and 4 weeks (initial series), followed by booster doses at 6, 12, 18 months and then yearly. Oral ciprofloxacin (500 mg po bid) or doxycycline (100 mg po bid) is useful in cases of known or imminent exposure. Following confirmed exposure, all unimmunized individuals should receive three 0.5 ml SQ doses of vaccine over 30 days, while those vaccinated with < 3 doses prior to exposure should receive an immediate 0.5 ml booster. Anyone vaccinated with the initial 3-dose series in the previous 6 months does not require boosters. All exposed personnel should continue antibiotic therapy for 4 weeks. If vaccine is unavailable, antibiotics may be continued beyond 4 weeks and should be withdrawn only under medical supervision. Decontamination and Isolation: Drainage and secretion precautions should be practiced. Anthrax is not known to be transmitted via the aerosol route from person to person. Following invasive procedures or autopsy, instruments and surfaces should be thoroughly disinfected with a sporicidal agent (high-level disinfectants such as iodine or 0.5% sodium hypochlorite). Outbreak Control: Although anthrax spores may survive in the environment for many years, secondary aerosolization of such spores (such as by pedestrian movement or vehicular traffic) generally presents no problem for humans. The carcasses of animals dying in such an environment should be burned, and animals subsequently introduced into such an environment should be vaccinated. Meat, hides, and carcasses of animals in affected areas should not be consumed or handled by untrained and/or unvaccinated personnel. |