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The flashcards below were created by user
cornpops
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burden of diarrheal diseases
found in areas that lack access to safe drinking water
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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
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reservoir and transmission
- humans, non-human animals, environment
- primarily fecal-oral
- - fecal contamination of hands or food products
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diarrhea
more liquid bowel movements than normal for the individual in a day
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types of infectious diarrhea
- secretory diarrhea - acute, watery, lasts hours or day
- invasive (inflammatory) diarrhea - acute, bloody
- persistent diarrhea - lasts 14 days or longer
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human digestive system
- segregated from the internal body
- mediates selective exchange - absorb nutrients, exclude pathogens
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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
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rotavirus
- leading cause of severe, acute diarrhea among infants and young children
- dsRNA
- 5 species (A-E) - Type A causes most infections in humans
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rotavirus epidemiology
- reservoir = human
- transmission = fecal-oral
- - small infectious dose, can survive a long time on hands, intermediate vehicles important
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rotavirus pathogenesis
infect small intestine, cause inflammation -> blunting of microvilli
immunity - most children have antibody by age 2
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rotavirus clinical manifestations
- diarrhea
- occasional vomiting
- additional risks for immunocompromised children
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rotavirus diagnosis and treatment
diagnosis - enzyme immunoassay, latex agglutination, DNA probes, RT-PCR
treatment - IV fluids, oral rehydration therapy
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norovirus
- ssRNA
- 5 distinct genotypes, 3 infect humans
- most common cause of outbreaks of viral gastroenteritis in adults
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norovirus reservoir and transmission
reservoir = human
- transmission = fecal-oral
- -infectious vomit, food, low infectious dose, survives well on surfaces, resistant to disinfectants
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norovirus pathogenesis
- small intestine disease
- immunity - most people seem highly susceptible to infection
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norovirus clinical manifestations
- milder than rotavirus
- vomiting
- diarrhea
- shorter duration of symptoms
- occasional deaths
- asymptomatic infection
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norovirus diagnosis and treatment
diagnosis - clinical, RT-PCR
treatment - oral rehydration with fluids, IV fluids, palliative (antisecretory agents)
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norovirus prevention
- food-handler restrictions
- food and water precautions
- person-to-person and environmental control
- no vaccine
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cholera
- severe, watery diarrhea
- caused by Vibrio cholerae
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cholera types
biotypes = classical and El Tor - based on agglutination
serotypes = based on O antigens,
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cholera reservoir and transmission
reservoir = free-living in brackish waters and estuaries, associated with copepods
- transmission = fecal-oral
- - water usually intermediate vehicle
- sometimes food
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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
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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
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cholera diagnosis and treatment
diagnosis - clinical, rapid test kits, culture
treatment - oral rehydration therapy
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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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