Do you remember we learned about how science proved worms make kids stupid? It turned out worms can cause you cancer as well. In his article, Man Killed by His Tapeworm’s cancer in usa.com, Quinn reported that the tumors found in a Colombian man was not composed of human cells.
According to November 5th issue of the New England Journal of Medicine, in January 2013, 41 years old Colombian man presented with “fatigue, fever, cough, and weight loss of several month’s duration.” He was diagnosed with HIV in 2006 and was not being treated properly. This showed that the man’s immune system was not healthy. However, the study further reports that a CT scan showed tumors in his lungs, adrenal glands and lymph nodes, and stool examination showed H. nana eggs. H. nana, known as dwarf tapeworm, is the most common human tapeworm that can mature and self-reproduce inside the intestine. After dozens of tests, the researchers found tapeworm DNA in the tumors, which was “10 times smaller than human cancer cells.” The man slipped into coma and died 72 hours after the diagnosis of tapeworm cancer due to kidney failure.This was the very first documented and known case of “a person becoming sick from cancer cells that developed in a parasite.”
So, what are the correlations? Direct causality would be H. nana’s cancer caused his immune system to further weaken to death. Reverse causality would be his weak immune system caused H. nana’s cancer. Confounding of third variable could be his genes, non-adherence to HIV therapy, or unsanitary environment. And of course, it might have been a chance.
However, could you believe if I told you all four worked together? First, it is Colombia unsanitary environment that infected him with H. nana. Second, according to Dr. Atis Muehlenbachs, from the Centers for Disease Control and Prevention, H. nana’s cancer did kill him. However, it was only because his non-adherence to HIV therapy immunosuppressed him that when H. nana multiplied and reproduced in his gut, H. nana’s cells mutated and proliferated as malignant cancer, instead of dividing to create a new tapeworm. Further, his weak immune system couldn’t keep the cancer cells in his guts and caused them to spread to his other organs. Lastly, according to World Health Organization’s 2013 data, there are 35 million people people living with HIV/AIDS; moreover, up to 75 million people are estimated to be infected with parasites, however, very few parasites are able to self-reproduce with their hosts. Of all these people, this Colombian guy not only had HIV, was infected with self-reproducing parasites, and died of both. That’s one bad stroke of luck.
I researched more on how worms could do more than just make kids stupid and found out that there are parasites known to cause cholangiocarcinoma, liver/bile duct cancer. They are called Clonorchis sinensis and Opisthorchis viverrini. According to The Tumorigenic Liver Fluke Opisthorchis viverrini -multiple Pathways to Cancer, published in 2012, they are common in less developed Asian countries, where an estimate of 40 million people are infected by eating raw or uncooked fish that are already infected with these tiny parasites, liver flukes. These parasites can reside in their hosts’ bile duct for 10 years. Therefore, the activities of these parasites could wear away the lining of the bile duct and cause scarring. This can further cause bacterial infections that block bile duct, enlarged liver, and/or cancer.
Adapted from http://www.dpd.cdc.gov/DPDx/HTML/Opisthorchiasis.htm
Honestly, I am not too worried about being infected with parasites, although they can cause death. This is because it seems like worms are common in developing countries. What I got out of these studies is not only that worms cause cancer but that we need to figure out ways to provide clean water to those in need.