Tapeworms whose eggs turn cancerous within the body. Wonderful.
Wash your hands & cook raw vegetables
A report in the New England Journal of Medicine details this latest aid to sleepless nights. It involves a collaboration between Dr Atis Muehlenbachs of the US Centers of Disease Control (who had picked up the original case) and Dr Peter Olson of the Natural History Museum, London (a specialist in dwarf tapeworms) (hmm).
The Centers for Disease Control and Prevention (CDC) is based in Atlanta, Georgia, USA & is the leading Federal Health agency in the USA & worldwide.
The Natural History Museum (NHM), London is probably best known for it’s collection of dinosaurs housed at Cromwell Road, South Kensington (the building is almost as wonderful as the vast array of natural history exhibits that it houses). You really should read the Wikipedia entry on the NHM; it’s early history is a hoot. It is funded by the Government & has 850 staff; many of those (such as Dr Olson) are world-renowned experts on some aspect of natural history.
This story began in January 2013 with a 41-year old man in a hospital in Medellin, Columbia. He had fatigue, fever, cough, and a weight loss of several months’ duration. In addition, he had been diagnosed with a HIV infection in 2006, but had not adhered to his treatment plan. There were H. nana eggs and Blastocystis hominis cysts in his poo. CT scans showed lung, liver and adrenal (a gland above the kidneys) nodules. In short, all the signs of multiple, malignant cancer, with one problem: no conventional cancer cells on biopsy (not human, and just a tenth of the size of a human cell). The Columbian doctors consulted with the CDC via telediagnosis plus sent them paraffin-embedded tissues.
It took months for the CDC to be able to unravel the mystery. Eventually, molecular testing identified high levels of tapeworm DNA in the tumours (which is when Dr Olson got involved). Unfortunately for the patient the delays were fatal; three days after the worm DNA was discovered he died.
Prepare now to get horrified... This starts bad & steadily gets worse.
The dwarf tapeworm H. nana is the most popular human tapeworm worldwide. Up to 75 million people are estimated to be carriers. In some parts of the world, it is estimated that ¼ of all children are infected (are you boiling those veg?). Worse, the infection is typically asymptomatic (the host does not know that they are infected).
H. nana is unique among tapeworms in that it can complete its life cycle in the small intestine, without the need for an intermediate host.
A H. nana infection is generally limited to the gastrointestinal tract. The BBC spoke to Dr Olson, and he explained that around 90% of the worm’s body is given over to reproduction as it spews out thousands of eggs into the small intestine every day. The internal lining of the intestine contains many thousands of villi (the word comes from the Latin & means "shaggy hair"). Those tapeworm embryos invade the villi. Whilst within the villi they transform into larvae. At that stage they then break out of the villi as young tapeworms & attach to the mucosal lining of the small intestine, just like their parents. In this way, a single tapeworm infestation can exponentially proliferate into a very high parasitic burden.
The previous paragraph has sketched out the normal development of a tapeworm infestation, and that is one of the conditions suffered by the Medellin patient. However, in his case one or more H. nana embryos themselves developed cancer (note: not the patient himself, but a tapeworm embryo within his body developed cancer). Thus, the patient died from tapeworm tumours.
The CDC/NHM speculation is that one (or more?) H. nana embryos penetrated beyond the villi & entered the patient’s body. Whilst there it became cancerous and--in the classic pattern which defines cancerous cells--duplicated itself repetitively, forming cancerous nodules. That cancerous infestation became malignant, and thus further cancer nodules began to form elsewhere in the body, eventually over-whelming his body’s defences & killing the patient.
This is the first known case of human-located tumours formed from cancerous parasitic worm tissue. The article authors speculate that many other cases could exist worldwide, but are occurring undiagnosed.
--------- Alex Kemp