Biological Terrorism Anthrax

1. Biological Terrorism Anthrax

2. History • Caused by Bacillus anthracis • Human zoonotic disease • Spores found in soil worldwide • Primarily disease of herbivorous animals • Sheep, goats, cattle • Many large documented epizootics • Occasional human disease • Epidemics have occurred but uncommon • Rare in developed world

3. Bioweapon Potential • Many countries have weaponized anthrax • Former bioweapon programs • U.S.S.R.,U.S.,U.K., and Japan • Recent bioweapon programs • Iraq • Attempted uses as bioterrorism agent • WW I: Germans inoculated Allied livestock • WW II: Alleged Japanese use on prisoners

4. Bioweapon Potential • Features of anthrax suitable as BT agent • Fairly easy to obtain, produce and store • Spores easily dispersed as aerosol • Moderately infectious • High mortality for inhalational (86-100%)

5. Bioweapon Potential • Aerosol method of delivery • Most likely method expected in BT attack • Would cause primarily inhalational disease • Spores reside on particles of 1-5 μm size • Optimal size for deposition into alveoli • Form of disease with highest mortality • Would infect the largest number of people

6. Bioweapon Potential • Dispersed as powder • Frequent letter hoaxes since 1997 • Recent letter deliveries • Highest risk is for cutaneous • Inhalational theoretically possible • Particle size • Likelihood of aerosolization • GI theoretically possible • Spores > hands > eating without handwashing

7. Bioweapon Potential • Sverdlovsk, Russia 1979 • Accidental release from anthrax drying plant • 79 human cases • All downwind of plant • 68 deaths • Some infected with multiples strains

8. Bioweapon Potential • Estimated effects of inhalational anthrax • 100 kg spores released over city size of Washington DC • 130,000 – 3 million deaths depending on weather conditions • Economic impact • $26.2 billion/100,000 exposed people

9. Epidemiology • Three forms of natural disease • Inhalational • Rare (<5%) • Most likely encountered in bioterrorism event • Cutaneous • Most common (95%) • Direct contact of spores on skin • Gastrointestinal • Rare (<5%), never reported in U.S. • Ingestion

10. Epidemiology • All ages and genders affected • Occurs worldwide • Endemic areas - Africa, Asia • True incidence not known • World 20,000-100,000 in 1958 • U.S. 235 total reported cases 1955-1994 • 18 cases inhalational since 1900, last one 1976 • Until 2001, last previous case cutaneous 1992

11. Epidemiology • Mortality • Inhalational 86-100% (despite treatment) • Era of crude intensive supportive care • Cutaneous <5% (treated) – 20% (untreated) • GI approaches 100%

12. Epidemiology • Incubation Period • Time from exposure to symptoms • Very variable for inhalational • 2-43 days reported • Theoretically may be up to 100 days • Delayed germination of spores

13. Epidemiology • Human cases – historical risk factors • Agricultural • Exposure to livestock • Occupational • Exposure to wool and hides • Woolsorter’s disease = inhalational anthrax • Rarely laboratory-acquired

14. Epidemiology • Transmission • No human-to-human • Naturally occurring cases • Skin exposure • Ingestion • Airborne • Bioterrorism • Aerosol (likely) • Small volume powder (possible) • Foodborne (unlikely)

15. Epidemiology • Transmission • Inhalational • Handling hides/skins of infected animals • Microbiology laboratory • Intentional aerosol release • Small volume powdered form • In letters, packages, etc • Questionable risk, probably small

16. Epidemiology • Transmission • Cutaneous • Handling hides/skins of infected animals • Bites from arthropods (very rare) • Handling powdered form in letters, etc. • Intentional aerosol release • May see some cutaneous if large-scale

17. Epidemiology • Transmission • Gastrointestinal • Ingestion of meat from infected animal • Ingestion of intentionally contaminated food • Not likely in large scale • Spores not as viable in large volumes of water • Ingestion from powder-contaminated hands • Inhalational of spores on particles >5 m • Land in oropharynx

18. Microbiology • Bacillus anthracis • Aerobic, Gram positive rod • Long (1-10μm), thin (0.5-2.5μm) • Forms inert spores when exposed to O2 • Infectious form, hardy • Approx 1μm in size • Vegetative bacillus state in vivo • Result of spore germination • Non-infectious, fragile

19. Microbiology • Colony characteristics • Large (4-5mm) • Nonhemolytic • Opaque white, gray • Retain shape when manipulated (“egg white”) • Forms capsule at 37º C, 5-20% CO2

20. Microbiology • Classification • Same family: B. cereus, B. thuringiensis • Differentiation from other Bacillus species • Non-motile • Non β-hemolytic on blood agar • Does not ferment salicin • Note: Gram positive rods are usually labeled as “contaminants” by micro labs

21. Microbiology • Environmental Survival • Spores are hardy • Resistant to drying, boiling <10 minutes • Survive for years in soil • Still viable for decades in perma-frost • Favorable soil factors for spore viability • High moisture • Organic content • Alkaline pH • High calcium concentration

22. Microbiology • Virulence Factors • All necessary for full virulence • Two plasmids • Capsule (plasmid pXO2) • Antiphagocytic • 3 Exotoxin components (plasmid pXO1) • Protective Antigen • Edema Factor • Lethal Factor

23. Microbiology • Protective Antigen • Binds Edema Factor to form Edema Toxin • Facilitates entry of Edema Toxin into cells • Edema Factor • Massive edema by increasing intracellular cAMP • Also inhibits neutrophil function • Lethal Factor • Stimulates macrophage release of TNF-α, IL-1β • Initiates cascade of events leading to sepsis

24. Pathogenesis • Disease requires entry of spores into body • Exposure does not always cause disease • Inoculation dose • Route of entry • Host immune status • May depend on pathogen strain characteristics

25. Pathogenesis • Forms of natural disease • Inhalational • Cutaneous • Gastrointestinal • Determined by route of entry • Disease occurs wherever spores germinate

26. Pathogenesis • Inhalational • Spores on particles 1-5 m • Inhaled and deposited into alveoli • Estimated LD50 = 2500 – 55,000 spores • Dose required for lethal infection in 50% exposed • Contained in imperceptibly small volume

27. Pathogenesis • Inhalational • Phagocytosed by alveolar macrophages • Migration to mediastinal/hilar lymph nodes • Germination into vegetative bacilli • Triggered by nutrient-rich environment • May be delayed up to 60 days • Factors not completely understood • Dose, host factors likely play a role • Antibiotic exposure may contribute • Delayed germination after antibiotic suppression

28. Pathogenesis • Inhalational • Vegetative bacillus is the virulent phase • Active toxin production • Hemorrhagic necrotizing mediastinitis • Hallmark of inhalational anthrax • Manifests as widened mediastinum on CXR • Does NOT cause pneumonia • Followed by high-grade bacteremia • Seeding of multiple organs, including meninges

29. Pathogenesis • Inhalational • Toxin production • Has usually begun by time of early symptoms • Stimulates cascade of inflammatory mediators • Sepsis • Multiorgan failure • DIC • Eventual cause of death • Symptoms mark critical mass of bacterial burden • Usually irreversible by this time • Clearance of bacteria unhelpful as toxin-mediated • Early research on antitoxin promising

30. Pathogenesis • Cutaneous • Spores in contact with skin • Entry through visible cuts or microtrauma • Germination in skin • Disease begins following germination • Toxin production • Local edema, erythema, necrosis, lymphocytic infiltrate • No abscess or suppurative lesions • Eventual eschar formation

31. Pathogenesis • Cutaneous • Systemic disease • Can occur, especially if untreated • Spores/bacteria carried to regional lymph nodes • Lymphangitis/lymphadenitis • Same syndrome as inhalational • Sepsis, multiorgan failure

32. Pathogenesis • Gastrointestinal • Spores contact mucosa • Oropharynx • Ingestion • Aerosolized particles >5 m • Intestinal mucosa – terminal ileum, cecum • Ingestion • Larger number of spores required for disease • Incubation period 2-5 days

33. Pathogenesis • Gastrointestinal • Spores migrate to lymphatics • Submucosal, mucosal lymphatic tissue • Mesenteric nodes • Germination to vegetative bacilli • Toxin production • Massive mucosal edema • Mucosal ulcers, necrosis • Death from perforation or systemic disease

34. Clinical Features • Symptoms depend on form of disease • Inhalational • Cutaneous • Gastrointestinal

35. Clinical Features • Inhalational • Asymptomatic incubation period • Duration 2-43 days, ~10 days in Sverdlovsk • Prodromal phase • Correlates with germination, toxin production • Nonspecific flu-like symptoms • Fever, malaise, myalgias • Dyspnea, nonproductive cough, mild chest discomfort • Duration several hours to ~3 days • Can have transient resolution before next phase

36. Clinical Features • Inhalational • Fulminant Phase • Correlates with high-grade bacteremia/toxemia • Critically Ill • Fever, diaphoresis • Respiratory distress/failure, cyanosis • Septic shock, multiorgan failure, DIC • 50% develop hemorrhagic meningitis • Headache, meningismus, delirium, coma • May be most prominent finding • Usually progresses to death in <36 hrs • Mean time from symptom onset to death ~3 days

37. Clinical Features • Laboratory Findings • Gram positive bacilli in direct blood smear • Electrolyte imbalances common • Radiographic Findings • Widened mediastinum • Minimal or no infiltrates • Can appear during prodrome phase

38. Clinical Features • Cutaneous • Most common areas of exposure • Hands/arms • Neck/head • Incubation period • 3-5 days typical • 12 days maximum

39. Clinical Features • Cutaneous – progression of painless lesions Papule – pruritic Vesicle/bulla Ulcer – contains organisms, sig. edema Eschar – black, rarely scars 24-36 hrs days

40. Clinical Features • Cutaneous • Systemic disease may develop • Lymphangitis and lymphadenopathy • If untreated, can progress to sepsis, death

41. Clinical Features • Gastrointestinal • Oropharyngeal • Oral or esophageal ulcer • Regional lymphadenopathy • Edema, ascites • Sepsis • Abdominal • Early symptoms - nausea, vomiting, malaise • Late - hematochezia, acute abdomen, ascites

42. Diagnosis • Early diagnosis is difficult • Non specific symptoms • Initially mild • No readily available rapid specific tests

43. Diagnosis • Presumptive diagnosis • History of possible exposure • Typical signs & symptoms • Rapidly progressing nonspecific illness • Widened mediastinum on CXR • Large Gram+ bacilli from specimens • Can be seen on Gram stain if hi-grade bacteremia • Appropriate colonial morphology • Necrotizing mediastinitis, meningitis at autopsy

44. Diagnosis • Definitive diagnosis • Direct culture on standard blood agar • Gold standard, widely available • Alert lab to work up Gram + bacilli if found • 6-24 hours to grow • Sensitivity depends on severity, prior antibiotic • Blood, fluid from skin lesions, pleural fluid, CSF, ascites • Sputum unlikely to be helpful (not a pneumonia) • Very high specificity if non-motile, non-hemolytic • Requires biochemical tests for >99% confirmation • Available at Reference laboratories

45. Diagnosis • Definitive diagnosis • Rapid confirmatory tests • Role is to confirm if cultures are negative • Currently available only at CDC • Polymerase Chain Reaction (PCR) • Hi sensitivity and specificity • Detects DNA • Viable bacteria/spores not required • Immunohistochemical stains • Most clinical specimens can be used

46. Diagnosis • Other diagnostic tests • Anthraxin skin test • Chemical extract of nonpathogenic B. anthracis • Subdermal injection • 82% sensitivity for cases within 3 days symptoms • 99% sensitivity 4 weeks after symptom onset • Not much experience with use in U.S. – not used

47. Diagnosis • Testing for exposure • Nasal swabs • Can detect spores prior to illness • Currently used only as epidemiologic tool • Decision for PEP based on exposure risk • May be useful for antibiotic sensitivity in exposed • Culture on standard media • Swabs of nares and facial skin • Serologies • May be useful from epidemiologic standpoint • Investigational – only available at CDC

48. Diagnosis • Environmental samples • Suspicious powders • Must be sent to reference laboratories as part of epidemiologic/criminal investigation • Assessed using cultures, stains, PCR • Air sampling • First responders • Handheld immunoassays • Not validated • Useful for detecting massive contamination

49. Diagnosis

50. Inhalational Influenza Pneumonia Community-acquired Atypical Pneumonic tularemia Pneumonic plague Mediastinitis Bacterial meningitis Thoracic aortic aneurysm Expect if anthrax Flu rapid diagnostic – More severe in young pts No infiltrate No prior surgery Bloody CSF with GPBs Fever Differential Diagnosis