Several parasites have been identified as causes of cancer in humans. The most well-established carcinogenic parasites are:
## Trematodes (Flukes)
**Schistosoma haematobium**
– Causes urinary bladder cancer
– Prevalent in Africa and the Middle East
– Classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC)[1][6]
**Opisthorchis viverrini**
– Causes cholangiocarcinoma (bile duct cancer)
– Endemic in Southeast Asia, particularly northern Thailand
– Classified as a Group 1 carcinogen by IARC[2][6]
**Clonorchis sinensis**
– Also causes cholangiocarcinoma
– Endemic in China and Korea
– Classified as a Group 2A carcinogen (“probably” carcinogenic) by IARC[2][6]
## Other Potentially Carcinogenic Parasites
While not definitively proven, several other parasites have been associated with cancer development:
**Schistosoma japonicum**
– Linked to colorectal cancer and hepatocellular carcinoma
– Classified as a possible (Group 2B) carcinogen by IARC[6][9]
**Plasmodium falciparum**
– Associated with Burkitt lymphoma (indirectly)
– Classified as a probable (Group 2A) carcinogen by IARC[6][9]
**Opisthorchis felineus**
– Associated with bile duct cancer in Russia[6]
**Strongyloides stercoralis**
– Potentially linked to HTLV-1-induced lymphomas/leukemias and colon adenocarcinoma[9]
**Toxoplasma gondii**
– Suspected association with various tumors, including pituitary adenoma and ocular tumors[1]
**Cryptosporidium parvum**
– Associated with colorectal carcinoma[6]
It’s important to note that while these parasites have been linked to cancer development, the mechanisms are often complex and may involve chronic inflammation, oxidative stress, and interactions with other pathogens or environmental factors[9]. Prevention and early treatment of parasitic infections are crucial in reducing the risk of associated cancers.
Citations:
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC3671432/
[2] https://thewaitingroom.karger.com/knowledge-transfer/the-link-between-parasitic-fluke-infections-and-cancer/
[3] https://www.frontiersin.org/news/2019/03/27/helminth-worms-cause-cancer
[4] https://www.parasite-journal.org/articles/parasite/full_html/2012/02/parasite2012192p101/parasite2012192p101.html
[5] https://pubmed.ncbi.nlm.nih.gov/29052139/
[6] https://en.wikipedia.org/wiki/Carcinogenic_parasite
[7] https://portlandpress.com/bioscirep/article/38/5/BSR20180935/88561/Parasites-as-negative-regulators-of-cancer
[8] https://archive.cdc.gov/www_cdc_gov/media/releases/2015/p1104-parasite-tumors.html
[9] https://pmc.ncbi.nlm.nih.gov/articles/PMC5233816/
[10] https://www.cancer.org/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/parasites.html