Anthrax

Anthrax is an acute zoonosis caused by Bacillus anthracis, primarily a disease of herbivores (cattle, sheep, horses). Humans become infected after contact with sick animals. Mainly cutaneous anthrax, then pulmonary and intestinal; it may be complicated by bacteremia and meningitis with high fatality. Natural cases have declined with economic development and improved sanitation, but anthrax has been used as a bioweapon. From September 22 to November 28, 2001, the US had multiple bioterrorism anthrax events: 23 cases (12 cutaneous, 11 inhalation), 5 deaths, all inhalation. Anthrax damages host tissues with hemorrhagic infiltration, necrosis, and severe edema plus systemic toxemia. Its high infectivity and fatality make it a major global concern.

Common Symptoms

Vesicle; bleeding tendency; pleural effusion; dyspnea; septicemia; convulsions; toxemia; eschar; pruritus

Causes and Pathogenesis

(1) Etiology: Respiratory infection initially resembles a common cold/flu for days, then progresses to severe/fatal respiratory failure; without immediate post-exposure treatment, mortality is nearly 100%; the lethal inhaled dose is 10,000-20,000 spores. Historically it affected ranch workers handling livestock excreta/hides, hence woolsorter's disease. Cutaneous anthrax appears 1-2 weeks after infection as an itchy lesion/black eschar progressing to a large painless necrotic ulcer (painlessness distinguishes it); untreated fatality is 20% but nearly zero with treatment. Intestinal infection causes hematemesis, severe diarrhea, acute enteritis, and anorexia; untreated fatality is 100%. (2) Pathogenesis: When resistance declines (malnutrition, chronic disease), spores enter skin wounds/respiratory/digestive tracts, germinate, and produce toxins. Healthy hosts with low spore burden may have asymptomatic infection. Protective antigen/capsule allow survival and transport to nodes; proliferation causes bacteremia. Two toxin proteins increase host susceptibility and inhibit neutrophils. Toxin directly damages microvascular endothelium increasing permeability, reducing effective volume and microperfusion, causing hypercoagulability, DIC, and septic shock; the organism also mechanically obstructs capillaries causing thrombosis. Main pathology is hemorrhagic infiltration, necrosis, and edema; cutaneous anthrax is carbuncle-like; lungs show capillary thrombosis with gelatinous mediastinitis; intestinal lesions center on the ileocecal valve; meninges show intense congestion with inflammatory cells and organisms in the subarachnoid space.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Health education: 1. Manage sources: isolate suspected patients, especially pulmonary anthrax; report immediately; burn secretions, excreta, dressings, leftover food, and room waste; cremate corpses; handle sick/dead animals the same way; quarantine livestock from endemic areas for 5 days; veterinary supervision at all stages. 2. Cut transmission: disinfect contaminated hides with iodine, chloride of lime, chloramine, ethylene oxide, or peracetic acid; disinfect wastewater; centralize waste wool; factories should be outside villages, downwind, away from water. 3. Protect susceptibles: workers and veterinarians should know prevention methods; wear protective clothing/masks; no smoking/eating; wash/disinfecct after work; treat skin wounds immediately with 2% iodine tincture; antibiotics for close contacts/carriers. 4. Vaccination: China uses the live attenuated percutaneous scarification vaccine giving immunity within 2 days lasting 1 year; emergency vaccination during outbreaks; A16R spore aerosol vaccination (100 million organisms/person, >80% seroconversion) is safe and effective; the best measure is vaccinating animals in endemic areas.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.