Traveller’s diarrhoea is most commonly caused by
**Core Concept**
Traveller’s diarrhoea is a gastrointestinal disorder that occurs in individuals visiting or living in areas with inadequate sanitation, contaminated water, and poor food handling practices. The condition is characterized by a sudden onset of loose, watery stools, often accompanied by abdominal cramps, bloating, and fever.
**Why the Correct Answer is Right**
The most common cause of traveller’s diarrhoea is bacterial infection, particularly by enterotoxigenic *Escherichia coli* (ETEC). ETEC produces heat-labile (LT) and heat-stable (ST) toxins that stimulate the intestinal mucosa to secrete excess water and electrolytes, leading to diarrhoea. Other bacterial pathogens, such as *Salmonella*, *Shigella*, and *Campylobacter*, can also contribute to traveller’s diarrhoea.
**Why Each Wrong Option is Incorrect**
**Option A:** Viral gastroenteritis, caused by rotaviruses, noroviruses, and adenoviruses, is a leading cause of diarrhoea worldwide but is not the most common cause of traveller’s diarrhoea.
**Option B:** Fungal infections, such as *Candida*, are opportunistic pathogens that can cause diarrhoea in immunocompromised individuals but are not typically associated with traveller’s diarrhoea.
**Option C:** Parasitic infections, like giardiasis and cryptosporidiosis, can cause diarrhoea in individuals travelling to areas with poor sanitation, but they are less common causes of traveller’s diarrhoea.
**Clinical Pearl / High-Yield Fact**
To prevent traveller’s diarrhoea, it is essential to practice good hygiene, such as washing hands frequently with soap and water, avoiding undercooked or raw meat, and choosing safe food and water sources.
**Correct Answer:** C. Campylobacter.