viral diarrhea
TRANSCRIPT
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Viral Diarrhea
Chris E. Forsmark, M.D.
Division of Gastroenterology, Hepatology, and Nutrition
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Virus Types
• Viral gastroenteritis– Rotavirus– Caliciviruses– Adenovirus– Astrovirus– Others (Torovirus, coronavirus,pestivirus)
• Viral colitis– Cytomegalovirus
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Magnitude of the Problem
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0-5 mo 6-11 mo 1 yr 2 yr 3 yr 4 yr
Episodes/yr
Bull WHO 1992
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Magnitude of the Problem
• Developing countries– 2.6 episodes/child/year in children < 5– 700 million episodes/year– 3-5 million deaths/year
• United States– Approx 180,000 hospitalizations/year in
children < 5– Mortality rare
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Viral Gastroenteritis in Children
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Rotavirus
• Discovered in 1973
• Worldwide distribution
• All children exposed by age 4-5
• Double stranded RNA virus
• Several groups (A-E vs G-P)
• Most common cause of viral diarrhea– 35% hospitalized, 10% community
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Rotavirus
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Rotavirus
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Rotavirus
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Rotavirus structure
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Transmission of Rotavirus
• Fecal-oral
• Contaminated water supplies
• Poor hygiene
• Food
• Fomites
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Rotavirus: Clinical Syndromes
• Childhood gastroenteritis– Endemic in tropics– Winter in temperate zone
• Outbreaks– Day care centers– Hospitals
• Immunocompromised adults
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How does Rotavirus cause diarrhea?
• Injures intestinal epithelium– Malabsorption
• Increases secretion by epithelium
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Diarrhea Classification• Pathophysiology
– Osmotic– Secretory– Exudation– Abnormal motility
• Duration– Acute (< 6 weeks)– Chronic (> 6 weeks)
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Osmotic diarrhea
• Def: Increased amounts of poorly absorbed, osmotically active solutes in gut lumen
• Interferes with reabsorption of water
• Solutes are ingested– magnesium– sorbitol– malabsorption of food (mucosal injury, lactase
deficiency)
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Secretory diarrhea
• Excess secretion of electrolytes, fluid across mucosa
• Usually coupled with decrease in absorption
• Watery, high-volume diarrhea with dehydration
• Enterotoxins: Cholera, E. coli, food poisoning, Rotavirus (?), Norwalk virus (?)
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Rotavirus Clinical Syndromes
• Asymptomatic carriers• Diarrheal illness
– 2-3 day incubation period
– diarrhea, vomiting fever 3-7 days
– high infectivity
• Complications– dehydration
– chronic diarrhea
– dissemination
– NEC
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Diagnosis of rotavirus
• Electron microscopy– Small intestine– Stool
• Antigen in stool– commercial ELISA– research PCR, nucleic acid probes
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Therapy for rotavirus
• Rehydration– ORT– Intravenous
• Probiotics– lactobacilllus GG
• Bismuth
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Oral rehydration solutions
Components WHO Ricelyte Pedialyte
Na (mEq/L) 90 50 45
K (mEq/L) 20 25 20
Cl (mEq/L) 80 45 35
Citrate (mEq/L) 30 34 30
Glucose (g/L) 20 30 25
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Prevention of Rotavirus
• Natural immunity 93% protective (sIgA)
• Vaccination– heterologous rotavirus (bovine, rhesus)– reassortment rotavirus (rhesus-human)– nonreplicating particles– naked DNA
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Calicivirus
• Norwalk virus and “Norwalk-like”
• “Sapporo-like” viruses
• Vesivirus
• Lagovirus
• All single stranded RNA viruses
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Norwalk virus
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Norwalk virus
• “winter vomiting disease” 1968, Norwalk OH
• Cause 40% of nonbacterial epidemics
• Explosive epidemics– camps, cruise ships, nursing homes
• Food borne illness– raw shellfish
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Food-borne illnessAgent 1981-89 1990-98Norwalk 33% 45%
C. perfringens 14% 12%
Salmonella 11% 11%
Staph areus 7% 3%
B cereus 7% 2%
Campylobacter 4% 3%
E Coli 0157 1% 4%
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Shellfish-borne infections
Agent 1894-1990 1991-98Norwalk 3% 52%
Vibrio 2% 37%
Unidentified 56% 7%
Salmonella 23% 0%
Hepatitis A 13% < 1%
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Norwalk virus: Clinical Features• 24-48 hour incubation period
• vomiting prominent
• diarrhea 1-3 days
• less severe than rotavirus
• affects all ages– antibodies in 60% of adults
• complications rare– immunocompromised
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How does Norwalk virus cause diarrhea?
• Infection affects proximal small bowel
• Patchy mucosal injury
• Malabsorption
• ? Excess secretion
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Norwalk virus
Before ingestion 2 days 6 days
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Diagnosis of Norwalk virus
• Clinical diagnosis (exclude rotavirus)
• Immune EM
• Serology of antibody response
• enzyme immunoassays
• RT-PCR
• oligonucleotide probes
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Treatment of Norwalk virus
• Rehydration
• Supportive measures– bismuth– antidiarrheals (Lomotil, Immodium)
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Other viruses causing gastroenteritis
• Astrovirus– children, outbreaks
• Adenovirus– children, prolonged course
• Torovirus– children, bovine pathogen
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Cytomegalovirus
• Herpesvirus
• Immune competent– Mononucleosis-type syndrome
• Immunocompromised– retinitis– hepatitis– gastrointestinal involvement (colon)
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Cytomegalovirus colitis