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19 Cards in this Set
- Front
- Back
Anthrax
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• Caused by Bacillus anthracis, a non-motile Gram-positive rod
• Natural disease of herbivores • Produces three exotoxins: – Edema factor – Lethal factor – Protective antigen • Not contagious |
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Cutaneous Anthrax
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• Route of infection: Direct inoculation of spores
• Incubation period: 1-7 days (may be up to 14 d) • Clinical findings – Pruritic macule -> vesicle ->round ulcer -> black eschar over 1-2 weeks – Surrounding edema/erythema but painless – +/- painful regional lymphadenopathy • Untreated, ~ 5%-20% fatality rate |
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Cutaneous Anthrax: Diagnosis
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• Vesicular fluid or border of skin lesion:
– Gram stain, culture and sensitivity – PCR • Skin biopsy – Culture and PCR (fresh frozen) – Immunohistochemistry (formalin-fixed) • Serology: – Acute- and convalescent-phase serum IgG (ELISA IgG antibody against protective antigen) |
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Inhalational Anthrax
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• Route of infection: Inhalation of spores (1-5 microns in size) into terminal bronchioles and alveoli
• Incubation period ~ 1-6 d (range 1- ?100 d) |
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Inhalational Anthrax
Pathogenesis |
• Once deposited, inert spores reside within alveoli (days – weeks)
• Spores taken up by alveolar macrophages -> regional lymph nodes • Spores germinate, producing vegetative cells that proliferate within macrophages, produce toxins and enter the bloodstream |
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Inhalational Anthrax
Clinical manifestations |
• Initial symptoms resemble “flu”
• Late symptoms include high fevers, vomiting, respiratory distress, and necrotizing hemorrhagic mediastinitis • Fatal within 24-36 hours if treatment delayed |
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Inhalational Anthrax
Diagnosis |
• Non-specific physical findings
• CXR: mediastinal adenopathy, pleural effusions • Gm stain/culture (or PCR) of blood, pleural fluid, and CSF – Large Gm (+) rods – Rough, grayish colonies - non-hemolytic, non-motile • Suspect cultures should be sent to NYCDOH/CDC |
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Inhalational Anthrax
Treatment |
• Antibiotics are effective against vegetative B. anthracis but not against the spore form
• Mortality rate 100% despite aggressive Rx in “advanced disease” but is lower with early treatment |
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Anthrax Vaccine
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• Culture supernatant (protective antigen) of attenuated, non-encapsulated strain
• Protective against cutaneous (human data) and possibly inhalational anthrax (animal data) • Injections at 0, 2, 4 wks & 6, 12, 18 mos; followed by yearly boosters • 83% serologic response after 3 doses, 100% after 5 • Current vaccine supplies are limited |
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Inhalational Anthrax
Prevention |
• Primary prevention
Vaccination of persons most at risk for exposure to anthrax spores • Post exposure prophylaxis Vaccination of persons who have been exposed to aerosolized anthrax spores to prevent delayed spore germination and inhalational disease |
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Anthrax
Post-Exposure Prophylaxis |
• Disease can be prevented as long as therapeutic antibiotic levels maintained until all spores cleared or controlled by immune defenses
• Viable spores demonstrated in mediastinal lymph nodes of monkeys 100d post-exposure • Start oral antibiotics ASAP after exposure – Antibiotics for 100 days without vaccine – Antibiotics for 30 days with 3 doses of vaccine (0, 2 and 4 weeks) |
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Smallpox as a Bioterrorist Weapon
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• Infectious via aerosol
• Rapid person-to-person transmission • Worldwide immunity has waned • Severe morbidity and mortality • Clinical inexperience • Potential to overwhelm medical care and public health systems (large-scale vaccine campaigns) |
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Smallpox
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• Incubation period 12-14 d (range 7-17 d)
• Vaccination of contacts within 4 days of exposure is effective in preventing illness • Contagiousness begins with onset of rash • Isolation measures effective in controlling outbreaks even with limited vaccine use |
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Smallpox
Pathogenesis |
• Implantation on oral or respiratory mucosa
• Migration to regional lymph nodes • Initial asymptomatic viremia – day 3 or 4 • Multiplication in reticuloendothelial tissues • Secondary symptomatic viremia – ~ day 8 |
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Smallpox
Clinical Features |
• Incubation period is 12-14 days (7-17d)
• Abrupt onset of high fever, malaise, rigors, vomiting, backache, and headache • Followed in 2-3 d by maculopapular rash • Generally not infective until rash appears |
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Smallpox
Exanthem |
• Maculopapular rash
• Starts on face (including oral mucosa), forearms, or pharynx (centrifugal distribution) • Spreads to trunk and legs • Lesions on palms and soles common • Macules/papules -> vesicles -> pustules • Synchronous development • Deeply embedded in dermis |
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Smallpox
Diagnosis |
• Requires astute diagnostician to distinguish from varicella or erythema multiforme
• Swab of vesicular/pustular fluid or removal of scab for culture, EM, variola-specific PCR assay at CDC BSL4 laboratory |
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Smallpox v Chickenpox
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Small pox
• Incubation 7-17 days • Prodrome 2-4 days • Distribution Centrifugal • Evolution Synch • Depth of lesion Dermal Chicken pox • Incubation 14-21 days • Prodrome Minimal • Distribution Centripetal • Evolution Asynch • Depth of lesion SubQ |
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Smallpox
Medical Management |
• Even one suspect case is an international emergency requiring immediate reporting to public health authorities
• Strict quarantine with both respiratory and wound isolation (negative airflow pressure and HEPA filtration) • No proven Rx (cidofovir effective in vitro) |