MI4.1-4 | Diarrhoea & Dysentery — Summary & Reflection

REFLECT

Consider a community outbreak affecting 40 persons after a wedding feast. Which data points would help you decide between cholera, Shigella, viral diarrhoea, and food poisoning? Think through: incubation period, stool character, age distribution, attack rate, and the role of a single common source versus person-to-person spread. How would your empirical treatment differ if you had to act before laboratory results?

KEY TAKEAWAYS

Key takeaways from this SDL:

1. Definitions: Diarrhoea = ≥3 loose stools/day (secretory); dysentery = bloody/mucoid stools with tenesmus (invasive).
2. Spectrum of agents: Bacterial (Vibrio, Shigella, ETEC, Salmonella, Campylobacter), viral (Rotavirus #1 in Indian children, Norovirus for outbreaks), parasitic (E. histolytica, Giardia, Cryptosporidium).
3. Vibrio cholerae: Comma rod, TCBS yellow colonies, cholera toxin → ↑cAMP → massive rice-water stool.
4. Shigella: Very low infective dose, Shiga toxin in S. dysenteriae type 1, flask-shaped ulcers, PMNs in stool.
5. E. histolytica: Erythrophagocytosis = pathognomonic; cysts 4-nucleate; distinguish from E. dispar by PCR/antigen EIA.
6. Rotavirus: Winter peak, children, wheel-like EM, NSP4 enterotoxin, vaccine available.
7. Laboratory: Stool character + microscopy guides likely pathogen; TCBS for Vibrio; MacConkey/XLD for Shigella/Salmonella; fresh wet mount for parasites within 30 min.