The most common causative organism for Traveller’s diarrhoea is –
**Core Concept**
Traveller's diarrhoea is a common condition characterized by the passage of loose, watery stools, often accompanied by abdominal cramps, bloating, and urgency. The condition is typically caused by the ingestion of pathogens, such as bacteria, viruses, or parasites, that are commonly found in contaminated food and water.
**Why the Correct Answer is Right**
The most common causative organism for Traveller's diarrhoea is **Enterotoxigenic Escherichia coli (ETEC)**. ETEC produces heat-labile (LT) and heat-stable (ST) enterotoxins that stimulate the intestinal mucosa to secrete water and electrolytes, resulting in diarrhoea. This pathogen is commonly found in developing countries and is often associated with the consumption of contaminated food and water. ETEC is a major cause of diarrhoeal disease in travellers, especially those visiting areas with poor sanitation and hygiene.
**Why Each Wrong Option is Incorrect**
**Option A:** **Salmonella** is a common cause of food poisoning, but it is not the most common causative organism for Traveller's diarrhoea. While Salmonella can cause diarrhoea, it is often associated with specific food sources, such as poultry or eggs.
**Option B:** **Norovirus** is a common cause of viral gastroenteritis, but it is not typically associated with Traveller's diarrhoea. Norovirus is often spread through person-to-person contact or contaminated food and water, but it is not the most common cause of diarrhoea in travellers.
**Option C:** **Giardia lamblia** is a parasite that can cause diarrhoea, but it is not the most common causative organism for Traveller's diarrhoea. Giardia is often associated with contaminated water sources, but it is not as common as ETEC in causing diarrhoea in travellers.
**Clinical Pearl / High-Yield Fact**
ETEC is the most common cause of diarrhoeal disease in travellers, especially those visiting developing countries with poor sanitation and hygiene. To prevent ETEC infection, travellers should practice good hygiene, such as washing their hands regularly, avoiding undercooked food and water, and choosing reputable food and water sources.
**Correct Answer:** C.