Toxoplasma Parasite a Cure for Cancer?

Joanne Lynn Intile, DVM, MS, DACVIM
Published: August 12, 2014
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“Could cat feces help cure cancer?” My eyes widened as they scanned over the title of the website I’d stumbled across.

After pausing for a few moments to recover my composure and swallow a mild wave of nausea, I rolled my eyes sarcastically and thought, “Yet another misinterpretation of sound medical research written in the name of Internet propaganda for the sake of promoting Dr. Google.”

Yet, as I continued to read further, I found myself intrigued by the concept behind the scientists’ work. The experiments were (thankfully) not designed to establish cat poop as a cure-all for cancer, but rather on using a common intestinal parasite (sometimes found in cat poop) called Toxoplasma gondii to battle tumor cells.

Toxoplasma gondii (T. gondii) is a relatively simple organism found in the digestive tracts of many mammals. T. gondii can cause toxoplasmosis, a disease that is usually not a life-threatening condition, but which can result in flu-like symptoms and malaise. In immunocompromised people or animals, toxoplasmosis can be a much more serious problem, and in very rare cases, can even be fatal.

Infection with T. gondii occurs via four main mechanisms:

  • Ingestion of  T. gondii tissue cysts in undercooked meat
  • Ingestion of material contaminated with T. gondii oocysts
  • Via a blood transfusion or organ transplant
  • Transplacental transmission from a pregnant female to her offspring

T. gondii can infect any mammal, but as in real estate for people and single-celled parasites, it’s all about location, location, location. T. gondii thrives in the intestines of cats, and it's our feline friends who are considered the primary hosts for this creature.

Oocysts, which are the “offspring” of adult T. gondii, are shed in the feces of infected animals, including cats. This is the reason why doctors tell pregnant women to avoid scooping their cats’ litter boxes. If they were to become infected by accidentally ingesting oocysts shed in the waste, they could experience a miscarriage.

So what does this all have to do with cancer?

Regardless of the the cell of origin, cancer exists to some extent because the host’s immune system fails to recognize tumor cells as being “different” from healthy cells. Cancer cells work very hard to evade immune reactions and do this by two main mechanisms — they either work to suppress immune reactions or they work to keep themselves appearing as “normal” as possible.

Conventional anti-cancer treatments such as chemotherapy or radiation therapy work by causing damage to cells in a non-specific manner. These modalities attack both healthy and tumor cells with nearly equal fervor. This leads to issues with toxicity and also greatly limits the doses that can be administered safely.

These latter factors have led to a great interest in developing targeted therapies for treating cancer, including options immunotherapy (for example:…). Immunotherapy anti-cancer treatments attempt to use the host’s own immune system to fight off cancer cells in a specific and controlled manner.

The theory behind using T. gondii as an anti-cancer treatment stems from its ability to elicit a strong immune response within the host; a response designed to fight off the infection. By infecting people or animals who have cancer with the parasite, the hope is that the patient’s immune system will be more effectively primed to battle tumor cells previously hidden from attack.

Research with T. gondii has shown anti-tumor activity in mice with ovarian carcinoma and melanoma. Tumors were confirmed to reduce in size, and mice treated with T. gondii developed potent immune reactions. Perhaps the most exciting data showed that the mice with melanoma whose tumors reduced in size following treatment with T. gondii maintained their ability to withstand new tumor development when re-challenged with melanoma cells later on.

The long-term goal for the researchers is to develop an anti-cancer vaccine containing the weakened T. gondii organism. Unlike conventional vaccines, T. gondii will be used as a treatment for cancer, rather than a preventative measure.

I do question the efficacy of the vaccine in people and/or animals that have been previously exposed to T. gondii. Up to one-third of humans and many household pets test positive for prior contact with the parasite. I would be concerned that those individuals would already have immune systems that are geared towards fighting off T. gondii, and may actually eradicate it before enough time has passed to stimulate the immune response necessary to kill tumor cells.

Fortunately, treatment with T. gondii does not involve feces, feline or otherwise. Also reassuring is the strain of T. gondii used in the research is a purified and attenuated (meaning weakened) version of the organism that cannot replicate within the host and should not lead to the development of toxoplasmosis.

As for cat-poop being the cure all, I’ve leave you with my parting advice: Make sure to keep gloves on and maintain pristine hygiene when you scoop the litter box. And keep on hugging your feline friends with fervor. You never know when you might need one of them to save your life!

Dr. Joanne Intile


Could cat feces help cure cancer?; Medical News Today

Image: Olesya Kuznetsova / Shutterstock