Can parasites cause cancer?
- Parasites are a type of infection that need to live on, or in another animal to survive
- Three parasites can cause liver and bladder cancer
- In the UK, cancers caused by these infections are very rare, and other things you can do are more likely to reduce your risk of cancer
Three types of parasite can cause cancer in humans. They are:
- Two small liver worms (Clonorchis sinensis and Opisthorchis viverrini)
They can cause bile duct cancer (a type of liver cancer). The parasites are more common in certain regions, such as Asian countries China, Thailand, Korea, Vietnam, Laos and Cambodia. Both these parasites are spread through contaminated food, particularly through undercooked fish.
- A blood worm (Schistosoma haematobium)
It can cause bladder cancer. It is common in Sub-Saharan Africa and the Middle East. This parasite lives in water in these regions, so it is best not to swim in slow-flowing waters there to avoid infection.
All three of these parasites are very rare in the UK, and very few cases of cancers will be caused by them.
More research is needed to understand how parasites cause cancer. But, it’s likely they disrupt the normal function of cells in a number of ways. For example, they could encourage cells to divide more than usual, or stay alive longer. Inflammation caused by the parasites can also lead to damage.
If you’re concerned about your exposure to these parasites, you can talk to your GP.
International Agency for Research on Cancer. Monographs on the Evaluation of Carcinogenic Risks to Humans: Biological Agents. Vol 100 B. (2012).
Brown et al. The fraction of cancers attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. Br J Cancer. 118, 1130-1141 (2018).