5. Diarrheal Diseases

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cornpops
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94752
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5. Diarrheal Diseases
Updated:
2011-07-26 05:07:41
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PH162A midterm2
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public health microbiology midterm 2 lecture 5
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  1. burden of diarrheal diseases
    found in areas that lack access to safe drinking water
  2. developed vs. developing countries
    • developing countries:
    • suffer most of burden from diarrheal diseases
    • majority of mortality

    • developed countries:
    • burden is mostly economic
    • contributing factors - centralization of food production and large food distribution network
  3. reservoir and transmission
    • humans, non-human animals, environment
    • primarily fecal-oral
    • - fecal contamination of hands or food products
  4. diarrhea
    more liquid bowel movements than normal for the individual in a day
  5. types of infectious diarrhea
    • secretory diarrhea - acute, watery, lasts hours or day
    • invasive (inflammatory) diarrhea - acute, bloody
    • persistent diarrhea - lasts 14 days or longer
  6. human digestive system
    • segregated from the internal body
    • mediates selective exchange - absorb nutrients, exclude pathogens
  7. defenses of the digestive system
    • high acidity of stomach
    • antibody IgA
    • phagocytic cells and tissues rich in lymphocytes underneath the mucosal membrane
    • endogenous (commensal) organisms in the intestine - compete with pathogens for nutrients, space, can have direct antimicrobial effects on pathogens
  8. rotavirus
    • leading cause of severe, acute diarrhea among infants and young children
    • dsRNA
    • 5 species (A-E) - Type A causes most infections in humans
  9. rotavirus epidemiology
    • reservoir = human
    • transmission = fecal-oral
    • - small infectious dose, can survive a long time on hands, intermediate vehicles important
  10. rotavirus pathogenesis
    infect small intestine, cause inflammation -> blunting of microvilli

    immunity - most children have antibody by age 2
  11. rotavirus clinical manifestations
    • diarrhea
    • occasional vomiting
    • additional risks for immunocompromised children
  12. rotavirus diagnosis and treatment
    diagnosis - enzyme immunoassay, latex agglutination, DNA probes, RT-PCR

    treatment - IV fluids, oral rehydration therapy
  13. rotavirus prevention
    • breastfeeding
    • vaccines
  14. norovirus
    • ssRNA
    • 5 distinct genotypes, 3 infect humans
    • most common cause of outbreaks of viral gastroenteritis in adults
  15. norovirus reservoir and transmission
    reservoir = human

    • transmission = fecal-oral
    • -infectious vomit, food, low infectious dose, survives well on surfaces, resistant to disinfectants
  16. norovirus pathogenesis
    • small intestine disease
    • immunity - most people seem highly susceptible to infection
  17. norovirus clinical manifestations
    • milder than rotavirus
    • vomiting
    • diarrhea
    • shorter duration of symptoms
    • occasional deaths
    • asymptomatic infection
  18. norovirus diagnosis and treatment
    diagnosis - clinical, RT-PCR

    treatment - oral rehydration with fluids, IV fluids, palliative (antisecretory agents)
  19. norovirus prevention
    • food-handler restrictions
    • food and water precautions
    • person-to-person and environmental control
    • no vaccine
  20. cholera
    • severe, watery diarrhea
    • caused by Vibrio cholerae
  21. cholera types
    biotypes = classical and El Tor - based on agglutination

    serotypes = based on O antigens,
  22. cholera reservoir and transmission
    reservoir = free-living in brackish waters and estuaries, associated with copepods

    • transmission = fecal-oral
    • - water usually intermediate vehicle
    • sometimes food
  23. cholera risk factors
    • residence in cholera endemic area
    • host factors - gastric acidity, blood group O, bottle feeding infants
    • strain factor - El Tor more asymptomatic infection
  24. cholera pathogenesis
    • infects small intestine
    • adherence factors = toxin co-regulated pilus, other pili
    • cholera toxin - activates adenylate cyclase, increased cAMP
    • infection can provide long-term immunity against same biotype
  25. cholera diagnosis and treatment
    diagnosis - clinical, rapid test kits, culture

    treatment - oral rehydration therapy
  26. cholera prevention
    • patients - disinfection of feces and anything it contacts
    • warnings about contaminated water sources
    • proper sewage treatment
    • water purification
    • surveillance to identify epidemics
    • vaccines

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