plague, anthrax.ppt
- 1. Plague History & Significance 14th Century: “Black Death” responsible for >20 million deaths in Europe Used as a BW agent by Japan in WW II Studied by Soviet and, to a smaller extent, U.S. BW programs 1995: Larry Wayne Harris arrested for illicit procurement of culture via mail
- 2. Plague Epidemiology Caused by Yersinia pestis About 10-15 cases/year U.S. Mainly SW states Human plague occurs from bite of an infected flea (bubonic) Only pneumonic form of plague is spread person- to-person Last case of person-to-person transmission in U.S. occurred in 1924
- 3. Yersinia Pestis Gram negative, non-motile, non- spore-forming bacillus Resistant to freezing temperature and drying, killed by heat and sunlight Source: Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases, Fort Collins, CO
- 4. Plague Case Definition Characterized by fever, chills, headache, malaise, prostration, & leukocytosis that manifests in one or more of the following clinical forms: ◦ Regional lymphadenitis (bubonic) ◦ Septicemia w/o evident bubo (septicemic) ◦ Plague pneumonia ◦ Pharyngitis & cervical lymphadenitis (pharyngeal) MMWR 1997;46(RR-10)
- 5. Plague Case Definition, cont. Laboratory criteria for diagnosis: Presumptive Elevated serum antibody titers to Y. pestis F1 antigen (w/o documented 4-fold change) in a patient with no history of plague vaccination OR Detection of F1 antigen in a clinical specimen by fluorescent assay Confirmatory Isolation of Y. pestis from a clinical specimen OR 4-fold or greater change in serum antibody titer to Y. pestis F1 antigen MMWR 1997;46(RR-10)
- 6. Plague: Case Classification Suspected: Clinically compatible case w/o presumptive or confirmatory lab results Probable: Clinically compatible case with presumptive lab results Confirmed: Clinically compatible case with confirmatory lab results MMWR 1997;46(RR-10)
- 7. Plague Clinical Forms Bubonic plague Most common naturally-occurring form Mortality 60% untreated, <5% treated Primary or secondary septicemic plague Pneumonic plague Most likely BT presentation From aerosol or septicemic spread to lungs Survival unlikely if treatment not initiated w/in 24 hours of the onset of symptoms
- 8. Pneumonic Plague Clinical Presentation Incubation: 1-6 days (usually 2-4 days) Acute onset of fever with cough, dyspnea, and chest pain Hemoptysis characteristic; watery or purulent sputum also possible Prominent GI symptoms may be present, including nausea, vomiting, diarrhea, and abdominal pain
- 9. Pneumonic Plague Clinical Presentation Other symptoms include headache, chills, malaise, myalgias Rarely, cervical bubo present Rapid progression to respiratory failure & shock
- 10. Bubonic Plague Incubation: 2-8 days Sudden onset nonspecific symptoms: fever, chills, malaise, muscle aches, headache Regional lymphadenitis (buboes) Swollen, very painful lymph nodes Typically inguinal, femoral, axillary, or cervical Erythema overlying skin May have surrounding edema Concurrent with or shortly after onset of other symptoms
- 11. Septicemic & Bubonic Plague Source: CDC NVBID
- 12. Plague Infection Control Person-to-person transmission via respiratory droplets Standard respiratory droplet precautions Treatment = 10 days antibiotics Case isolation for at least the first 48 hrs of antibiotic treatment Bubonic plague - standard precautions
- 13. Plague Infection Control Antibiotic prophylaxis for close contacts Duration: 7 days or duration of risk of exposure + 7 days Close contacts refusing prophylaxis: Observe 7 days after last exposure and treat if fever or cough develop Bubonic contacts: Observe 7d and treat if symptoms develop
- 14. Bacillus Species The genus Bacillus includes large aerobic, spore-forming, Gram-positive rods occurring in chains. Most members of this genus are saprophytic organisms prevalent in soil, water, air and on vegetation, such as Bacillus subtilis & B. cereus . Some are insect pathogens, such as B. thuringiensis . This organism is also capable of causing disease in humans. B. cereus can grow in foods and cause food poisoning by producing either an enterotoxin (diarrhea) or an emetic toxin (vomiting).
- 15. Morphology and identification A. Typical Organisms The typical cells, measuring 1 × 3–4 μm, have square ends and are arranged in long chains; spores are located in the center of the bacterial cell.
- 16. Colonies of B. anthracis are flat or slightly convex with irregular edge and have a ground-glass appearance in transmitted light. B. Culture Hemolysis is uncommon with B anthracis but common with B cereus. B. anthracis B. cereus …..Morphology and identification Gelatin is liquefied by B. cereus. B. anthracis growth in gelatin stabs resembles an inverted fir tree. Bacillus cereus colonies are large flat and dry.
- 17. Diagnostic Laboratory Tests Specimens to be examined are fluid or pus from a local lesion, blood, pleural fluid, and cerebrospinal fluid in inhalational anthrax associated with sepsis and stool or other intestinal contents in the case of gastrointestinal anthrax. • Stained smears Gram stain show chains of large gram-positive rods Culture When grown on blood agar plates, the organisms produce Non-hemolytic gray to white, tenacious colonies with a rough texture and a ground-glass appearance. Comma-shaped outgrowths (Medusa head, “curled hair”) may project from the colony. In semisolid medium, anthrax bacilli are always non- motile.
- 18. - Definitive identification requires lysis by a specific anthrax - bacteriophage, - Detection of the capsule by fluorescent antibody, - identification of toxin genes by polymerase chain reaction (PCR), - Enzyme-linked immunoassay (ELISA) Clinical laboratories that recover large gram-positive rods from blood, cerebrospinal fluid, or suspicious skin lesions, which phenotypically match the description of B anthracis as mentioned, should immediately contact their public health laboratory and send the organism for confirmation. …..Diagnostic Laboratory Tests