Protozoal Infection
Protozoal infections are caused by single-celled parasitic organisms called protozoa. They enter the body through contaminated food or water, insect bites, or direct contact, and can affect the gut, blood, liver, or skin depending on the species involved. Across tropical regions generally, these infections are among the more common reasons travellers and residents seek medical attention.
Key points
- Single-celled parasites responsible for giardiasis, amoebiasis and cryptosporidiosis commonly spread through contaminated food or water and target the digestive tract.
- Typical symptoms include persistent diarrhoea, bloating and cramping, though amoebiasis can occasionally spread to the liver and cause fever.
- Overlapping symptoms with other gut illnesses often mean a stool or blood test is needed before starting metronidazole or another antiprotozoal medicine.
Common forms and what they look like
The most frequently encountered protozoal infections include giardiasis, amoebiasis, and cryptosporidiosis, all of which target the digestive tract. Typical symptoms are persistent loose stools or diarrhoea, bloating, stomach cramps, nausea, and fatigue. Giardia infections often cause notably foul-smelling, greasy stools. Amoebiasis can occasionally spread beyond the gut to the liver, causing pain in the upper right abdomen and fever.
How protozoal infections are treated
Treatment depends on which organism is responsible, so a stool sample or blood test is usually needed to confirm the diagnosis. Many intestinal protozoal infections respond well to metronidazole, an antiprotozoal medicine that disrupts the parasite’s ability to survive. Because symptoms overlap with other gut illnesses, self-treatment without a diagnosis risks missing the right medicine entirely. If symptoms persist beyond a few days, include blood in stools, or are accompanied by high fever, seek medical assessment promptly.