Gastroenteritis Viruses

Question 1

Examples of gastroenteritis viruses

Answer 1

1. Rotavirus (reovirus - resp enteric orphan virus)
2. Norwalk virus (calcivirus)
3. Others - astrovirus, adenovirus, parvovirus

Question 2

Structure of rotavirus

Answer 2

• naked virions, double shelled capsid with icosahedral symmetry, characteristic wheel appearance
• ds RNA, 11 segments, capable of genetic reassortment

Question 3

Variations of rotavirus

Answer 3

• classified into groups A-E
• several human & animal serotypes eg G1-4, G9
• common antigens on inner capsid, type-specific antigens on outer capsid, neutralising antigen encoded by VP7 gene

Question 4

Epidemiology of rotavirus

Answer 4

• large viral load in stools - oral faecal transmission
• nosocomial
• may be asymptomatic before age 6m due to partially protective maternal Abs/IgA in breast milk
• most children have Abs by age 6

Question 5

Symptoms of rotavirus

Answer 5

1. Gastroenteritis - major causative agent in young children 6m - 2y
   - Diarrhea, vomiting, abdominal pain, fever, dehydration
   - Virus infects & damages absorptive epithelial enterocytes of small intestinal villi resulting in enzyme deficiency & defective transport

Question 6

Diagnosis of rotavirus (3)

Answer 6

1. Tissue Culture - difficult to propagate human strains
2. Viral Detection - stool specimen, EM, ELISA, latex agglutination, PCR, hybridization w cDNA probes
3. Serology
   - CFT
   - ELISA for specific IgM

Question 7

Treatment of rotavirus (4)

Answer 7

1. Oral live attenuated vaccines - good for inf that enter through GIT
   - RotaTea (Merck) - pentavalent, 3 doses
   - Rotarix (GSK) - monovalent, 2 doses
   - should complete vaccination by 6m of age
2. Omit bottled milk - nutrient rich, may cause sec infection
3. Correction of dehydration & electrolyte imbalance (ORS)
4. Prevent/reduce transmission
   - proper sanitation, clean water supply, breastfeeding
   - isolate cases, good hygiene practices in hospitals

Question 8

Features of Norwalk virus

Answer 8

• most important etiological agent of epidemic viral GE in adults - causes GE
• epidemics assoc w water, food, shellfish
• rapid onset, mild, self limiting, lasts 1-2 days, highly infectious
• diarrhea, fever, nausea, vomiting, abdominal cramps

Question 9

Diagnosis of Norwalk virus

Answer 9

• RT-PCR
• EM
• ELISA for detecting antibody

Question 10

Treatment of Norwalk virus

Answer 10

1. Supportive treatment - rehydration

2. No vaccine