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40 Cards in this Set
- Front
- Back
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What is the difference between acute vs. chronic gastroenteritis?
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Acute = rapid onset with or without accompanying symptoms; less than 2 weeks duration
Chronic = greater than 2 weeks duration |
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What is the difference between viral vs. bacterial diarrhea?
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Viral diarrhea is NOT usually bloody.
Viral gastroenteritis is more prevalent than bacterial. |
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All diarrheal viruses are naked or enveloped?
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Naked.
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Give examples of diarrheal viruses.
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Rotavirus
Calciviruses Astrovirus Enteric adenoviruses |
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What is the virus family and morphology of rotavirus?
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Family: Reoviridae
naked - dsRNA - segmented (11) double-shelled capsid (outer shell necessary for attachment) |
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Why is it called rotavirus?
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On EM looks like hubbed-wheel - "rota"
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What are some other reoviruses?
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Orthoreovirus -> minor GE
Orbivirus --> colorado tick fever |
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Which 2 surface proteins are present on the outer capsid of rotavirus and what is their significance?
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VP4 and VP7
- antibodies to these surface proteins are protective - VP4 determines P serotype - VP7 determines G serotype |
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What happens when the rotavirus attaches to a cell membrane?
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Cleavage of VP4 --> VP5 and VP8
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How are structural proteins synthesized from the dsRNA of rotavirus?
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RNA-dep RNA pol synthesizes mRNAs from the 11 segments;
dsRNA is made using ss mRNA as a template |
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What are viroplasms?
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Large inclusion bodies formed for viral assembly
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Where does the double-shelled rotavirus go after it aquires VP4?
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Buds into the rER where it aquires VP7 and accumulates in the lumen of the ER
*envelope from ER is lost with maturation |
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How is rotavirus spread?
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Fecal-oral
-outbreaks common in daycares and hospital settings -water borne -asymptomatic and symptomatic shedding -possibly resp secretions |
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Where is the major site of infection for rotavirus?
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After ingestion of virus it travels through the stomach to its major site of infection: the small intestine
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How does rotavirus cause diarrhea?
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Damage to enterocytes results in decreased absorption capacity and fluid loss
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What can occur secondary to enterocyte destruction?
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Sloughing of mature villous enterocytes results in brush border diarrhea leading to further fluid loss and metabloic acidosis
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What kind of immunity is elicited in rotavirus infection?
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Humoral and mucosal immunity is elicited.
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Can you be infected with rotavirus more than once?
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Most are infected in childhood but can be infected more than once even in the same season.
Protective immunity from initial infection is incomplete but will be less severe infection. |
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What are the clinical features of rotavirus?
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Abrupt onset of fever adn vomitting, followed by explosively watery diarrhea (non-bloody)
Mild dehydration, metabolic acidosis and electrolyte abnormal |
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What is used for rotavirus diagnosis?
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Rapid tests available to test for hospital outbreaks.
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What is treatment for rotavirus?
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Supportive.
Gradual re-introduction of feeding to prevent malnutrition. No antivirals. |
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How do you prevent rotavirus?
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It is highly stable in the environment.
Lysol and 95% alcohol effective. **Hand washing is single most effective measure! -contact isolation in hospitals |
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Why was the Rotashiled rotavirus vaccine removed?
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Released for routine immunization but removed after one year due to increased incidence of intussusception.
Now newly developed vaccines available - Rotateq, Rotarix --> G seroptypes 1-4 --> P serotype 8 |
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What is the morphology of calciviridae family?
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+ssRNA - naked
(lack of envelope = resistant to env like rotavirus) |
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What are some examples of calciviruses?
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Norovirus (found on cruise ships)
Snow mountain-like virus Sapporo-like virus Hep E virus |
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How are progeny replicated?
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Similar to rotavirus:
Replication and assembly in cytoplasm; particles released by host cell death |
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How is calcivirus spread?
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Fecal-oral.
Can be food or water borne No season, found in all ages. |
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What is the clinical manifestation of calciviruses?
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Clinical syndrome similar to rotavirus except with flu-like symptoms.
- usually shorter duration than rotavirus |
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How is calcivirus diagnosed? treated?
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No rapid test kits.
Research assays. Treat: Supportive and rehydration. NO VACCINE WASH HANDS |
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What is the morphology of astrovirus?
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Has a "star-shape" = 5-6 points
+ssRNA - naked Seven serotypes |
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What age group has highest attack rate of astrovirus?
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Highest rate in children under age 2 years.
-daycare outbreaks |
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What are the clinical manifestations of astrovirus?
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Indistinguishable from rotavirus except that the disease is milder.
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How is astrovirus diagnosed? treated?
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No rapid tests.
Research assays. Treat: supportive and oral rehydration. NO VACCINE |
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What is morphology of adenoviruses?
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Large - naked - dsDNA
Capsid has 12 pentons (antenna-like from vertices) |
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Which serotypes of adenovirus cause GE?
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Serotypes 40 and 41 are associated with GE.
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How common is enteric adenovirus?
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Second most common cause of viral GE in hospitalized patients.
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What are the clinical manifestations of enteric adenovirus?
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-Has longer incubation period than most enteric viruses. (8-10d)
-symptoms like other enteric viruses but with respiratory symptoms -low grade fever, vomitting and diarrhea |
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What is the gold-standard for diagnosis of adenovirus?
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Tissue culture BUT unlike other adenovirus serotypes, enteric adenovirus are not detected in tissue culture!!
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How are enteric adeno diagnosed?
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EM, rapid test kits, DNA probes
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How is enteric adenovirus treated?
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No antivirals.
Vaccine is available but not used routinely becuase only covers a few serotypes. (given to military) WASH HANDS |
