33: Bioterrorism – Anthrax & Smallpox – Flashcards
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advantages of biological agents as weapons
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easy to obtain (in soil!), inexpensive to produce, can disseminate over large geo area, overwhelm medical services and create panic, perpetrators escape easily
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ideal bioterrorism microbe
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infectious via aerosol, stable in environment, susceptible civial population, high morbidity and mortality, person-to-person transmission (plague, smallpox), difficult to Dx/Tx, previously developed for biowarfare
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Bacillus anthracis: microbial characteristics
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large aerobic spore-forming gram (+) rod
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bacillus vs corynebacterium on gram stain
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both gram (+) rods, but corynebacteria cluster together, vs bacillus are clean and separated
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cutaneous anthrax: transmission
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contact with spore-contaminates: textile, raw hides, etc.
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Dx: textile worker develops eschar
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cutaneous anthrax
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Dx: hide sorter develops painless black wound
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cutaneous anthrax
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cutaneous anthrax: clinical course
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inoculation > papular lesion > vesicular with surrounding edema > painless black eschar
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GI anthrax: transmission
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ingestion of contaminated/undercooked meat > spores germinate in intestine > after up to 1 week incubation, bloody diarrhea/fever/vomiting (severe gastroenteritis) with TREATED case fatality up to 75%!
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*inhalational anthrax: clinical course
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inhalation of anthrax spores > 3-40 day incubation period > nonspecific flu Sx >* TRANSIENT IMPROVEMENT > rapid deterioration: high fever, dyspnea, shock > death if untreated
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form of anthrax with transient improvement
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inhalational anthrax
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inhalational anthrax: pathogenesis
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inhalation of 2 um particles > ingestion by alveolar M0's > move to hilar LNs > germination, production of anthrax toxin > hemorrhagic necrosis of nodes and mediastinum (WIDENS); gelatinous pleural effusion, producing atelectasis (anthrax PS) > bacteremic seeding of other organs > hemorrhagic meningitis
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B. anthracis: virulence factors
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capsule (antiphagocytic) and 3 toxins: PA: B part of A-B toxin, cleaved on surface to provide channel for entry of EF (edema factor: activates adenylate cyclase > cAMP > EDEMA) and LF (MAPKK pathway > cell death)
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*telltale signs of inhalational anthrax
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widened mediastinum WITHOUT pulmonary infiltrates (pneumonia) since germination of spores occurs in hilar LNs, not lung; accompanying fever, tachycardia, tachypnea, "toxic" appearance
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how to confirm inhalational anthrax Dx
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sputum culture/PCR, CSF gram stain/culture (hemorrhagic meningitis), serology: IgG
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hemorrhagic mediastinal LNs on CT: Dx, and how to confirm
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inhalational anthrax; confirm with sputum culture/PCR, CSF gram stain/culture (hemorrhagic meningitis), serology: IgG
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patient with widened mediastinum on CXR: Dx, and how to confirm
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inhalational anthrax; confirm with sputum culture/PCR, CSF gram stain/culture (hemorrhagic meningitis), serology: IgG
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inhalational anthrax: treatment approach
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ciprofloxacin or doxycycline, PLUS additional Abx (vancomycin, Pen G) - treat for long enough to prevent germination of additional spores (2 months)
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cutaneous anthrax: treatment approach
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ciprofloxacin or doxycycline, no additional Abx, and only for 7-10 days
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anthrax: treatement and prevention for different types
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cutaneous: ciprofloxacin or doxycycline for 7-10 days; if inhalational, ADD additional Abx and extend for 60 days (logn enough to prevent germination of additional spores); PROPHYLAXIS: same Rx, > 60 days because spores can germinate well after exposure
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anthrax vaccine: component, and demographic
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against protective antigen; reserved for military and occupational exposures
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anthrax patients who require isolation
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NONE - not spread person-to-person (but spores remain viable for decades - an issue for vets and animal husbandry)
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cousins of smallpox virus
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vaccinia, molluscum contagiosum, cowpox
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smallpox virus: genome
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dsDNA
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eradication success of Smallpox
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success using vaccinia vaccine, but repositories maintained at CDC and Russia (possible bioterror agent because high potential for morbidity, mortality, person-to-person transmission, and unpreparedness)
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smallpox: transmission
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*infectious during rash, which follows fever (isolate at fever stage); person-to-person spread via aerosols/droplets, stays in fomites but dies in environment: up to 10 new cases per original case
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*when to isolate smallpox patients
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keep them at home, but stay away once they get fever - precedes rash stage, which is infectious
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smallpox: clinical course and infectivity
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1-3 week incubation, fever, then 2-3 days later: monomorphic nodular rash appears on mouth/face first, then spreads to trunk and legs; most infectious during first week of rash, when oral lesions (enanthem) ulcerate > ++ virus in saliva; no longer infectious after all scabs of rash have fallen off (3-4 weeks after rash onset)
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when is smallpox patient most infectious?
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oral rash (enanthem) - the lesions ulcerate and produce ++ virus in saliva
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smallpox: treatment, prognosis
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NO Rx (unlike anthrax); case-fatality ~ 30%
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*Dx: monomorphic nodular rash
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smallpox (vs chicken pox - different stages of maturity)
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major* vs minor features of smallpox
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*MAJOR: fever prodrome 1-4 days before nodular RASH that is MONOMORPHIC anywhere on body; minor criteria: first appears on mouth/face/forearms, with slow evolution; toxic appearance
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first sign of smallpox illness
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fever - when contacts need to be isolated
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chickenpox vs smallpox
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TIMELINE: similar incubation periods, but fever first in smallpox; LOCATION: chicken pox = trunk, smallpox = face/extremities, *including palms/soles; RASH: chicken pox: different stages, vs smallpox: monomorphic throughout body; DX: both can use culture/PCR of vesicular fluid, but smallpox Dx at CDC, vs chickenpox can also be Dx with serum IgM, Tzanck smear
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features of vaccinia virus
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live (unattenuated) strain that provides cross-immunity to smallpox virus
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*how to determine that smallpox vaccination was succsesful
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must be evidence that vaccinia virus has replicated in recipient: get "Jennerian vesicle" after ~ 1 week, which evolves to form a scab and falls off with scarring at week 3
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*side effects of smallpox vaccine
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flu-like with tender regional LNs; serious side-effects possible: viremia, encephalitis, eczema vaccinatum, myocarditis, autoinnoculation of other sites on body
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smallpox vaccine: contraindications
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patient or household contacts have immunosuppression, eczema (vaccine causes eczema vaccinatum); also allergy to Rx within vaccine
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smallpox public health approach
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isolate suspected cases in home and notify Health Dept; vaccinate during first few days after exposure - could be protective; then isolate when fever occurs
