Question
Enumerate viruses causing gastroenteritis. Add a note on Morphology, Pathogenesis ,Lab diagnosis and prevention of rotavirus infection (2+6)
Answer
Viruses causing gastroenteritis: Rotavirus (double-stranded RNA, Reoviridae — the leading cause of severe dehydrating diarrhoea in infants/young children); Norovirus (calicivirus — a leading cause of outbreaks in all age groups); Adenovirus (enteric serotypes 40/41); Astrovirus.
Rotavirus infection — morphology, pathogenesis, laboratory diagnosis, and prevention
Morphology: a non-enveloped, double-stranded, segmented (11 segments) RNA virus with a characteristic wheel-like (“rota” = wheel) triple-layered icosahedral capsid structure visible on electron microscopy — an outer capsid layer, an inner capsid layer, and a core layer enclosing the segmented genome.
Pathogenesis: the virus infects and damages mature enterocytes at the tips of small intestinal villi, causing villous atrophy/blunting, which reduces intestinal absorptive surface area and disaccharidase enzyme activity — producing an osmotic component to the diarrhoea (unabsorbed carbohydrate drawing water into the lumen); the viral NSP4 protein additionally acts as a viral enterotoxin, directly stimulating intestinal chloride secretion, contributing a secretory component as well.
Laboratory diagnosis: ELISA (antigen detection in stool) — the most widely used rapid method; electron microscopy of stool — historically important, direct visualization of the characteristic wheel-shaped virions, now largely superseded; RT-PCR — increasingly used, high sensitivity and allows genotyping.
Prevention: rotavirus vaccine (live attenuated oral vaccine — monovalent, pentavalent, or India’s indigenous ROTAVAC), given in early infancy (2–3 doses, e.g., 6, 10, 14 weeks); has dramatically reduced hospitalizations and mortality from severe rotavirus gastroenteritis; general hygiene/sanitation measures (hand hygiene, safe food/water) provide additional but less effective protection given the virus’s high environmental stability and low infectious dose.
Treatment: primarily supportive — oral or intravenous rehydration therapy, since no specific antiviral treatment is available.