Tapeworms are quite bad. They can infect people, lay eggs, and cause symptoms such as diarrhea and weakness. And they can guzzle the body for life. But clinicians are shocked to find that they can do something worse: infect people with tumors.
Researchers at the Centers for Disease Control and Prevention have discovered cancer cells that come from a common tapeworm that can take origin in people with a damaged immune system and source malignant-like tumors.
This is the first known case of a person infected with cancer cells offshoot from a parasite – in this case from Hymenolepis nana, a dwarf tapeworm.
Prevalence of Hymenolepis nana in humans
Almost 75 million people can be infected with H. nana at one time which indicates it is the most common tapeworm infection in humans. Humans become infected with tapeworms by eating food contaminated with rats or insects or by drinking the feces of another infected person.
Children are often affected. Most infected people are asymptomatic. Compromised immune systems functioning like HIV-infected people who consume steroids will develop tapeworms.
About 3,000 species of tapeworms are known to infect animals. However, H. nana is the only one that can complete its entire life from egg to adult tapeworm in the human gut. Therefore, the number of H. nana in the gut is multiplied, especially in people with a declining immune system and unable to fight against the parasite.
Researchers believe that a mechanism that allows parasites such as H. nana to escape the human immune system can reproduce tapeworm cells in Colombian humans uncontrollably.
H. nana infections are common in areas where hygiene and handwashing are difficult. When traveling in less developed regions, people should defend themselves by washing their hands with soap and warm water and washing, peeling, or cooking all raw vegetables and fruits in safe water before eating.
In 2013, Colombian doctors asked the CDC to help diagnose curious lung and lymph node biopsies in a 41-year-old HIV-positive man. Tumors look like human cancer, but initial CDC laboratory studies have shown that cancer-like cells are not human. This disclosure initiated an almost three-year search for the reason for the man’s infection.
Researchers at the Infectious Diseases Pathology Branch, a CDC unit that investigates cases of inexplicable morbidity and mortality, first asked if it was infrequent cancer or an anonymous infection.
The progression pattern is as clear as cancer, with many cells overcrowded into small spaces and proliferating rapidly. But the tiny cell sizes are about 10 times smaller than normal human cancer cells. The researchers also labeled the cells together, which is unusual for human cells.
They went through the research thoroughly – they did a lot of tests – before taking the DNA from H. nana tapeworm in a male tumor in mid-2013. Unfortunately, the male died 72 hours later.
Finding out how to help a patient with the same disease can be difficult for physicians – drugs to treat tapeworm infections may not be effective against tapeworm cancer cells in humans. It is unclear whether human cancer treatment will help, although scientists think it may be beneficial.
Clinicians in developing countries should be conscious of the potential for similar diseases, especially if they have patients with weak immune systems with tumors.