Chris Froome’s Parasite – What is Bilharzia Anyway?


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These Ethiopian children are receiving free antiparasitic medication at a clinic. Many of them have schistosomiasis. Image courtesy of US Army Africa: CC BY 2.0.

These Ethiopian children are receiving free antiparasitic medication at a clinic. Many of them have schistosomiasis. Image courtesy of US Army Africa: CC BY 2.0.

Where Did Chris Froome Get Schistosomiasis?

Schistosoma spp. only occur in certain places. Schistosomiasis is not directly transmissible from one human to another: the parasites have to have the snail in order to complete their life cycle. And schistosomes of humans depend on human urine and feces entering fresh surface waters. Where good sanitation exists, the parasites don’t flourish.

Hood quotes Froome as saying “I must have touched some contaminated water somewhere in Africa.”

Froome was born in Kenya and moved to South Africa in his teens. Both countries have S. haematobium, which lives near the bladder, and S. mansoni, which lives near the intestine. In a June 27 Telegraph article by Ian Chadband, Froome’s brother is quoted as saying that they used to fish and hunt in rice fields in Kenya.

“Those fields were riddled with bilharzia,” Chadband writes, “the debilitating parasitic infection which affected all three brothers for years and which seriously stunted Chris’s first years as a professional.”

So Froome’s 2010 bout with schistosomiasis was apparently not his first.

What is Schistosomiasis?

The symptoms of schistosomiasis are challenging to summarize because they vary widely between individuals, and at different stages of the disease. Some people have very few symptoms; some, especially those with many worms and long term untreated infections, suffer serious disability, even death. Unless he was unwise enough to go back into contaminated African waters recently, Froome is clearly well past the initial stages of the disease.

While eggs were making their way through the tissues to the bladder or intestine, Chris Froome may have felt generally unwell, with fever, rash, and abdominal pain. Many eggs don’t complete the trip, however, as the body’s immune system builds walls around them and traps them. Eggs that are carried off in the bloodstream become trapped in the liver, lungs, spleen, even the brain.

In chronic schistosomiasis these eggs trapped in organs, and  the immune response to them, can impede the flow of blood and cause serious disease. It is this chronic stage, caused by eggs in the bladder wall, intestinal wall, small blood vessels, and organs, that is responsible for the worst effects of the disease: lethargy, swollen abdomen, liver disease, lung disease, bladder cancer, seizures.

How Common is Schistosomiasis?

If Chris Froome has schistosomiasis, he’s got plenty of company. Far from being “almost unknown beyond rural Africa” as Hood’s article suggests, the World Health Organization estimates that 700 million of the world’s people are at risk of infection, with about 240 million infected.

Schistosomes known to infect humans are widespread in Africa and are also present in parts of the Middle East, South America, East and Southeast Asia, and the Caribbean.

Schistosomiasis is on the WHO list of neglected tropical diseases.

Bilharzia Treatment

Doctors use the drug praziquantel to treat schistosomiasis, typically in two or three doses for just one day. Although there have been sporadic reports of possible treatment failure, this approach usually eliminates the infection and side effects, if any, are typically mild and brief.

What praziquantel can’t do, even with repeated doses, is remove schistosome eggs that have been trapped in tissues and organs during a lengthy infection. Roberts and Janovy write in Foundations of Parasitology (2009) that:

“Appropriate chemotherapy can lead to reversal of and even resolution of much , but longstanding heavy infection can result in irreversible liver or bladder damage.”

Chris Froome’s Bilharzia

Although actual symptoms, diagnosis, and treatment are between the athlete and his medical team, with time spent in the habitat of this invasive parasite, Chris Froome’s bilharzia infection is much less unlikely than some have suggested.


Chadband, I. France 2013: The Incredible Rise of Chris Froome – and How He Was Almost Killed By a Hippo. (2013). The Telegraph. Accessed July 21. 2013.

Gilbert D. N. et al. The Sanford Guide to Antimicrobial Therapy 2011. (2011). Antimicrobial Therapy Inc.

Hood, A. Still Living With Bilharzia Parasite, Froome Says He Has No Drug Exemptions(2013). Velo News. Accessed July 21, 2013.

Roberts L. S. and Janovy, J. Jr. Foundations of Parasitology 8th ed. (2009). Boston: McGraw Hill.

World Health Organization. Schistosomiasis. Accessed July 21, 2013.

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