Thursday, 30 January 2014

Toxoplasma gondii - Andrew Alexander’s Terrifying Parasite

“I felt like Frankenstein,” Alice Smellie quotes Andrew Alexander in the MailOnline. The Downton Abbey star apparently picked up a “terrifying” parasite more than a year ago and waited months for a diagnosis. When that diagnosis came, it was disturbing, no doubt, but “terrifying” is a bit over the top. (Admittedly, the prevailing dramatic and negative response to anything parasitic could account for the terror.)

The series Downton Abbey is set in the early 1900s.
No one was worried about toxoplasmosis then, but
other parasites were much more common in England
  than they are today.
      Image by JB + UK_Planet; CC BY 2.0

Toxoplasma gondii, a Terrifying Parasite

Alexander had Toxoplasma gondii – often simply called toxoplasma. Smellie writes that the not-so-terrifying toxoplasmosis is actually “an incredibly common bacterial infection.” She’s right that it’s common; in fact, as many as a third of people living in the UK are infected with the parasite. But T. gondii is not a bacterium, it’s a protozoan.

What qualifies T gondii as a disturbing, and concerning, parasite? A handful of things:

  • It lives in your tissues, including the brain, and once you have it, you have it forever. 
  • A first exposure during pregnancy can have truly terrifying implications for the fetus. 
  • If you have it and your immune system falters (with AIDS for instance), reactivation of the infection can be fatal. 
  • There is evidence that T. gondii can change behavior, and it is implicated in some forms of mental illness. 
  • Acute infection can make you look like Frankenstein. (Well, it can cause swollen lymph nodes but it usually doesn’t).

Andrew Alexander’s Forever Parasite

Most people who walk around with T. gondii in their tissues never know they have it. The acute infection is typically mild and goes undiagnosed. Perhaps one or two in ten infected people have more severe symptoms like Alexander: flu-like symptoms with fever, headache, sore throat, achy muscles, swollen lymph nodes. Within a few weeks, even these people usually feel better, though it can take much longer.

When good health returns, it means that the immune system has won the battle – at least for now. The parasite is no longer multiplying rapidly and spreading; it has formed tiny cysts and basically gone dormant. In the parasite’s perfect world, a carnivore eventually eats the host and the parasite gets to infect that carnivore next. I suspect, however, that Andrew Alexander’s bradyzoites have reached a dead end.

How Did Andrew Alexander Catch Toxoplasma gondii?

Most people catch T. gondii in one of two ways:

  • By eating meat that is not fully cooked. Lots of people eat rare, or raw, meat; domestic and wild animals are often infected with T. gondii. The meat you buy from the butcher might well contain bradyzoites. 
  • By swallowing infective oocysts that have been passed in cat feces. Cats are the only host in which T. gondii multiplies sexually, and during acute infection, a cat passes millions of oocysts.

Smellie’s article relates that Alexander became ill after returning from Africa. Did he catch T. gondii there? Possibly. But he could have picked it up just about anywhere. This parasite is ubiquitous. Where was he one to three weeks before becoming ill? That’s where he got it.

Further reading:

Drisdelle, Rosemary. Parasites: Tales of Humanity's Most Unwelcome Guests. University of California Press. 2010

Smellie, Alice. "I looked like Frankenstein... the cast gathered round as if I was about to expire: Downton's Andrew Alexander reveals his battle with a terrifying parasitic infection." MailOnline; Oct 12, 2013.

"Toxoplasmosis: Toxoplasma Infection." The Center for Food Security and Public Health, Institute for International Cooperation in Animal Biologics. May 2005

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