It took three years of research to understand after the parasitic tapeworm spooked experts by transmitting cancer to its host, a likely rare set of circumstances that nonetheless happened.
- The 41 year-old man was HIV-positive when he presented to the hospital, compromising his immune system
- The CDC found a tapeworm was in his gut, carrying abnormal cancer cells
- The parasite’s cancerous cells caused tumors in its host due to the compromised immune system
- There are currently 75 million people with tapeworms, and 37 million people with HIV
Back in 2013, a 41 year-old man presented to the doctors in Colombia with a cough, fever, weight loss, and complaints of weakness. The patient was HIV-positive and reportedly had not been taking his medication. After biopsies, the medical health professionals found unusual cancerous cells in his lymph nodes and lungs.
While they were definitely cancer cells, they were 10 times smaller than those presenting in humans. They multiplied quickly, and some were even fusing together, which is highly uncommon for us. The doctors asked for help from researchers at the Centers for Disease Control and Prevention (CDC).
Dr. Atis Muehlenbachs, from the CDC’s Infectious Disease Pathology Branch (IDPB), that specifically investigates mysterious diseases, discovered the presence of a dwarf tapeworm (Hymenolepis nana) in the patient’s stool samples. According to the investigator, this was a highly unexpected find, considering it turned out the cancer was actually in the taperworm.
The dwarf tapeworm, or H. nana, is a parasitic transparent platyhelmith that can grow up to 44 millimeters in length, and 1 millimeters in width. It’s not an uncommon occurrence. In fact, out of all the 3,000 types of tapeworm, H. nana is the most frequently met. Due to its ability of completing its entire life cycle within the gut of its host, it’s a particularly successful kind of parasite.
Normally, its effects are very slight. The carriers will hardly be aware, and there are reportedly 75 million people currently infected. It’s only when the infection is particularly severe that symptoms appear, such as anorexia, headaches, diarrhea, and abdominal pain.
Its host, the 41 year old man, actually developed tumors due to the cancerous cells within the tapeworm, as found by Dr. Muehlenbachs. Unfortunately, the patient died 72 hours after being diagnosed. In spite of finding the cause, there was no time to save the patient, but has paved the way to a startling discovery.
It was never believed before that it was possible for a cancer-carrying parasite to cause tumors in a human host. The likely explanation for this highly unusual situation was suggested to happen in people with compromised immune systems. For example, the patient who was HIV-positive.
Due to the infection, the common parasite was able to transfer its incredibly abnormal cancer cells to the host. It’s particularly worrying because the dwarf tapeworm is the most frequently met, and there are currently around 37 million people around the world with HIV. Furthermore, it’s not the only condition that would compromise a human’s immune system.
This will likely open up new directions of investigation, adding tapeworms to the list of conditions that might heighten the risk for cancer.