Tuesday, December 15, 2009

I'll have my bear steak (or cougar) well-done, please

You don't hear much about trichinosis much these days.  But when I was a kid, you heard a lot more.  Maybe that was because my father was a doctor.

Trichinosis is a disease you used to get from eating undercooked pork.   In the 1930s, autopsies showed that one in six people in the US had been infected with Trichinella, the worm that causes trichinosis.

It's nasty.  Tiny worms are coiled up in little cysts (capsules) in the muscles of the pig.  When you eat the cysts, the worms are released into your gut, where they quickly mature, mate, and then release larvas.  Yes, the worms in your gut make you a little sick, but they don't last long before your immune system kicks them out.

Now for round two.  "The greatest injury occurs during the migration of the larvas, when half a billion or more of them may simultaneously bore through the body.  At this time there are excruciating muscular pains, muscular disturbance and weakness, fever, anemia, and swellings of various parts of the body.  It is during this stage of the disease that death may occur, and about a third of the sufferers die.  If the victim survives this period, the larvas become encysted and the symptoms subside, though there may be permanent damage to the muscles."*  The larvas head for the most active muscles in the body--the diaphragm, the eye muscles, the tongue.  Sometimes they even bore into the brain, although for most Americans, this is not considered an active "muscle."

A Canadian graduate student tried to murder his roommates by feeding them meat infected with Trichinella.

How do the pigs get the Trichinella worm?  They get it from eating pork scraps in their garbage, or from eating infected rats that croak on the farm.  An ounce of infected pork sausage may contain a hundred thousand encysted worms.*  Not a pretty picture.

So that's why we cook our pork well--and doubtless the reason why for centuries, customs of both Jews and Muslims have prohibited eating pork.

The first line of defense in the US is laws that require the cooking of any meat in garbage fed to pigs.  Of course, most people know enough to cook their pork thoroughly.   Consequently, the number of serious cases of trichinosis is down, and only about .013 of the pigs in the US are infected.

The wildlife connection

True, the little larvas coiled up inside muscles are hitchhiking in a pig, waiting for their chance to be eaten and mate in a glorious orgy inside the pig's gut.  But what does this have to do with wildlife?

"There are fewer than 10 cases of trichinosis a year in the United States, and in recent years, bear meat has accounted for almost all of the nonpork cases, according to a recent report from the Centers for Disease Control and Prevention.  Black bear, specifically.  Other infections came from walrus meat, deer, wild boar — and one case of cougar."

"Two patients who became ill said they had eaten raw bear meat while stuffing it into sausage. But most of the meat had been cooked: stir-fried, boiled, broiled, baked, microwaved or cooked over an open fire. In some cases, the meat was both boiled and fried."  Source  Apparently, the meat hadn't been cooked enough--it has to reach 160 degrees inside, so use a meat thermometer.  "Well-done" isn't good enough.

Now that trichinosis from pork has been largely eliminated, people are getting it from eating wild game.  Trichinosis is a disease of omnivores and carnivores--rats, bears, cougars,... and humans.

Knowing a little about trichinosis, besides saving your life, can help you navigate the debate about hunting and reintroducing predators like cougars or wolves.  T.R. Mader has a blog that crusades against predators, often with piles of fascinating facts, such as "54% of 899 Montana cougars tested positive for Trichinella."  He says that one reason against allowing cougar populations to increase is because cougars carry trichinosis--the "disease would be curtailed with predator control."

Big deal.  A couple of hunters a year are going to get trichinosis from eating the undercooked cougar they shot.  And if they are dumb enough to do that, they deserve a Darwin Award.

*Ralph Buchbaum.  Animals without Backbones.

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More fun and games
Case study of a woman with trichinosis.
Photo of trichinella cyst in muscle.

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