Chris Froome’s Parasite – What is Bilharzia Anyway?

Chris Froome is an outstanding athlete, despite having apparently suffered repeatedly with schistosomiasis. Image by Brian Townsley: CC BY 2.0

Chris Froome is an outstanding athlete, despite having apparently suffered repeatedly with schistosomiasis. Image by Brian Townsley: CC BY 2.0

About 160 years ago, Theodor Bilharz discovered the cause of a disease that manifested as chronic bloody urine, and thus gave that disease his name.

Although the term bilharzia is still used, today the disease is known as schistosomiasis in medical circles, and the tiny worms that cause it are Schistosoma spp., S. haematobium, S. mansoni; with S. japonicum being the most common.

According to a July 16 Velo News article by Andrew Hood, Tour de France yellow jersey leader, Chris Froome (Team Sky) “has been struggling with bilharzia over the past several seasons.”

Unfortunately, anyone hoping to learn anything about schistosomiasis from that article will come away considerably misinformed.

Bilharzia – The Parasite

The schistosomes are flukes that live in the blood. Male and female worms are typically found in pairs living in the small blood vessels around the bladder or intestine, depending on the species. Mature females deposit eggs in those vessels – eggs which may be swept away by the bloodstream, or may be lodged in blood vessel walls and eventually break through into surrounding tissue. Gradually they make their way through to the bladder lumen where urine collects, or the intestinal lumen, and are thence passed to the outside world with the urine or feces.

A pair of schistosomes magnified many times. The male wraps himself around the long thin female, seen lying diagonally at upper left. Image from Otis Historical Archives of “National Museum of Health & Medicine," CC BY 2.0.

This is a pair of schistosomes magnified many times. The male wraps himself around the long thin female, seen lying diagonally at upper left. Image from Otis Historical Archives of “National Museum of Health & Medicine,” CC BY 2.0.

The eggs do not hatch inside the human body and give rise to more parasites: they need fresh water and a snail host in order to develop. If they find their way into fresh water, the eggs hatch, releasing a microscopic swimming stage of the parasite, which will invade a snail if it finds the right species. Inside the snail, the parasites multiply, eventually releasing many swimming parasites that are now infective to humans.

This is the stage at which Chris Froome would have stepped into the water. He would not have seen the parasites, for they are far too small, but they are attracted to human skin and burrow through it quickly, entering the bloodstream and traveling to the liver. There, they mature for a time before migrating to the blood vessels where they will spend the rest of their lives producing eggs.

Click to Read Page Two: Where did Chris Froome Get Schistosomiasis?

© Copyright 2013 Rosemary Drisdelle, All rights Reserved. Written For: Decoded Science

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  • gtalcstories

    Mrs Drisdelle

    A few questions.

    Froome says he contracted the disease at some point in late 2009/early 2010, and he has recieved treatment for it on at least 4 occasions (December 2010, June 2011, March 2012, January 2013). He also says he will recieve another treatment of Biltricide after the tour. Does it surprise you that it has taken 4 treatments (5 by next time) and over 2 and a half years of treatment? Is this not unusually long ? and does it surprise you that over this period Froome has been able to compete right at the top of professional cycling.

    Secondly Froome has said repeatedly that Bilharzia is “never cured” that its “not something that disappears”. He explains this by saying (in that velonews article) that eggs hatch in the body and lay more eggs, thus becoming a never ending disease.

    Isn’t this completely wrong? Why is Froome so horribly misinformed about the disease that allegedly ruined the first half of his cycling career. Surely someone must have gave him this information as its quite a stretch to think that he made it all up himself.

    Also, what implications do you think having Bilharzia would have on the UCI biological passport? Doesn’t Bilharzia cause reduced hemoglobin/red cell ratio?

  • Rosemary Drisdelle

    Of course I can’t comment on any individual case, nor am I an infectious disease specialist. The literature indicates that repeated treatment with praziquantel (Biltricide) is typically not required (unless there’s reinfection, or the medication isn’t administered/taken properly).

    Schistosomiasis is, in a sense, incurable, if there is organ damage due to eggs remaining in the body. Thus, a person could suffer ill effects even if the worms themselves are gone. Whether or not this is true in any individual case depends on how many parasites there are, how long the person is infected, and how the immune system responds.

    Schistosome eggs do not hatch inside the body, and even if they did, the parasites could not mature to adults. The life cycle absolutely requires the snail intermediate host. But as I mentioned above, the eggs are a problem in other ways.

    Adult schistosomes do feed on the blood, and there is some evidence that blood parameters are affected. Again, how much would vary from one person to another.

    It’s not so unusual for someone to have a poor understanding of a medical condition. Parasites are complicated, and misunderstood even by many physicians. There is much misinformation about them.

    Thanks for your comments.