Tapeworm-derived tumours are extremely rare, says Olson, who has documented a handful of other cases in patients whose immune systems were compromised.
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H. nana is the most common tapeworm in humans, infecting up to 75 million people worldwide at any given time.
Scientists at the U.S. Centers for Disease Control and Prevention (CDC) said Wednesday they have found the first known case of a person becoming ill from cancer cells that arose in a common parasite. The biopsy revealed cells that acted like cancer but were smaller than any known human cancer cells.
We know that many creatures, such as various sea animals, are susceptible to cancer, while others, like elephants, are nearly immune to it. But until now, scientists had not believed that any human parasite could harbor cancer cells or transfer them to people. Tapeworms can be eliminated with drugs, but it’s not clear if those drugs would clear up tumors.
But since both HIV and dwarf-tapeworm infection are common in the developing world, the case raises concerns, the CDC team said: Similar cases, if they do occur, could be misdiagnosed as human cancer. The tumor cells additionally gave the impression to be fusing collectively, the researchers discovered – a habits not usually seen in human cells.
No one ever knew tapeworms could get cancer, either, but the cells were clearly malignant. Finally the researchers found in the cells the DNA from a type of tapeworm called H nana. “So we’re very eager to learn about other cases and potentially those that we might have an opportunity to attempt treatment”.
Investigator’s at the CDC’s Infectious Diseases Pathology Branch (IDPB) discovered that a patient’s odd cancer-like tumors had initially developed as cancer cells within a tapeworm (Hymenolepis nana). As they investigated, the patient got worse and he died a few months later.
Olson believes that the tumorous tapeworm cells are rogue larvae that burrowed from the stomach into the lymph nodes of immunocompromised people (a healthy immune system would stop this invasion).
The dwarf tapeworm can spend its entire life cycle inside the human gut.
Doctors believe that worm-cancer is rare, but know many cases could be going undiagnosed.
Ways to avoid infection include washing hands with soap and warm water and by washing, peeling, or cooking raw vegetables and fruits before eating.
Although the tumors appeared similar to a human cancer, laboratory tests found that the cancer cells weren’t human. “It represents an enormous advance in our knowledge and raises questions about the conditions under which cells may become cancerous”.
Instead of dividing rapidly to create a new, adult tapeworm, the cells proliferated as cancer.
But on closer inspection the cancerous cells were clearly not human – they were tiny at just a tenth of the size of a human cell.
DNA sequencing revealed that they belonged to a tapeworm, which puzzled researchers because they didn’t look like a tapeworm and were invading organs outside the gastrointestinal tract.
Eggs of the dwarf tapeworm (Hymenolepsi nana).
It could even be that tapeworm infections in people get mistaken for cancer, the researchers said.
To study the parasites, CDC researchers contacted Peter D. Olson, a tapeworm expert at the Natural History Museum in London, who provided information about the worms’ genetic data and helped interpret the findings. “This study is an example of natural history and public health experts working together to uncover fascinating new details about the natural world”, he said in a CDC statement.
The CDC came to that conclusion after being brought in to consult on a perplexing case of a 41-year-old man who sought medical attention in Medellín, Colombia, for a cough along with fatigue, fever, and weight loss.
That’s why Olson thinks the patient’s compromised immune system may be to blame for the tumors.
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HIV infection is also widespread in numerous same places. The tumors didn’t directly cause his death (kidney failure did), but they did contribute to his decline, Muehlenbachs said.
