Years ago, I happened to read “New Guinea Tapeworms and Jewish Grandmothers” by Dr. Robert Desowitz, an entertaining little book about… parasites.  Or rather, how ecological perturbations affect human relationships with them.  Not surprisingly, many of Dr. Desowitz’s anecdotes concerned well-intentioned but poorly thought-out interventions in the 3rd world.  For example, dams erected to provide cities with hydroelectric power frequently increased the incidence of schistosomiasis (”snail fever”) – a debilitating parasitic disease transmitted to humans by snails flourishing in the man-made reservoirs.  Likewise, irrigation systems often became breeding grounds for the mosquitos that transmit malaria. 

Of course, Desowitz didn’t neglect the developed world either: although schistosomiasis is non-existent in the US and malaria has largely been eradicated, there were other “critters” to write about: Giardia, tapeworms, pinworms, etc.  As various “gross out” ads for “detox” nostrums indicate, they’re never far away.  Even our relatively sanitized existence hasn’t eliminated them completely.

As it turns out, perhaps that’s not such a bad thing.  While those ubiquitous detox ads portray parasites as uniformly awful, the fact remains that human beings evolved with them.  And research has shown that pre-agricultural humans were likely pretty damn healthy, despite their presence.  Is it possible that parasites – at least certain kinds – may be relatively benign… or may even make some positive contribution(s) to the health of their hosts (i.e., us)?

That’s the message of this BBC article, which discusses some recent British/Vietnamese research:

Infection with hookworm and other parasitic worms is endemic in Vietnam, but rates of asthma and other allergies are low.

British and Vietnamese scientists gave local children treatment to clear their body of worms.

They found this led to an increase in dust mite allergy among the children.

Thanks to improved hygiene, practices parasitic worms have been mostly eradicated among human populations living in developed countries.

However, experts believe that over millions of years of co-evolution worms have found methods to dampen down host immune responses to prolong their own survival inside humans.

This relationship seems to have become so intertwined that without gut worms or other parasites, our immune system can become unbalanced, which, in turn, could contribute to the development of asthma and other allergies.

This reinforces something I wrote about earlier this year - it’s possible to be too hygienic.  Researchers like Dr. Joel Weinstock at Tufts University have pointed out the possible connection between intestinal worms and immune health via animal and human experiments. The above research provides some additional confirmation of this hypothesis… which may ultimately lead to a greater understanding of what makes the human immune system tick.

Because of the “ewwwww” factor, it can be tough to think of some parasites as our “pals”, but then again, life is full of surprises, ain’t it?

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