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In praise of parasites

By Kenneth R. Weiss, Knowable Magazine

Kevin Lafferty gets more than his share of intimate disclosures from strangers about their anatomy and bodily functions.

Graphic details and pictures arrive steadily via email, from people all over the world — a prison inmate in Florida, a social psychologist in Romania, a Californian afraid he picked up a nasty worm in Vietnam — begging for help, often after explaining that doctors will no longer listen. Do I have bugs burrowing into my brain? Insects poking around under my skin? Creatures inching through my intestines?

Lafferty has learned to open letters and packages carefully. On occasion, they contain skin or other suspect samples in alcohol-filled vials.

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“Sorry to hear about your health troubles,” Lafferty wrote recently to one man who asked him to help identify a worm found wriggling in the toilet bowl. “Undercooked fish (and squid) can expose you to many different types of larval parasites that … can accidentally infect humans, sometimes making people sick.”

“The photo that you sent does not look like a tapeworm (or a parasite) to me, but it is not sufficient quality for identification,” he gently informed another, whose email included extreme close-up pictures of a white, bumpy tongue and noted that emergency hospitals keep referring the stricken man to “psychiatry.”

Lafferty is not a medical doctor — he’s a PhD ecologist who studies parasites, mostly in fish and other marine creatures, a fact he’s always careful to explain to his correspondents. He’s sympathetic to these desperate people, even if what ails them is more imagined than real. Parasites, after all, have wormed into every corner of the tapestry of life, including hooking up with human beings in the most unpleasant of ways.

Yet his own view of parasites is more expansive than that of veterinarians, physicians and public health researchers, who tend to vilify these freeloading worms, bugs and protozoans as nasty culprits behind outbreaks of disease. Lafferty reminds us that parasites are not lesser life forms hell-bent on exploiting the weak and degraded, but rather an overlooked, misunderstood and even glorious part of nature. He celebrates them.

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“Don’t get me wrong, I don’t want to be parasitized and I wouldn’t wish it on others,” he says in his laboratory at the University of California, Santa Barbara. But over three decades of studying parasites he has grown to admire their ingenious and complex lifestyles as they hitch rides on hosts that swim, run, crawl, climb or fly around the globe. He cut his scientific teeth studying parasitic worms that castrate their hosts (and thus, from an evolutionary standpoint, transform them into the living dead). In recent years, he’s become enthralled by tiny parasites that brainwash those they infect, turning them into zombies or pushing the hosts to engage in crazy, life-threatening behavior.

“Many of them are fabulous examples of evolution,” he says, “and sometimes incredibly beautiful in terms of the things they do to make a living on this planet.”

Parasites have an underappreciated importance, he adds — as indicators and shapers of healthy ecosystems. They thrive where nature remains robust, their richness and abundance keeping pace with biodiversity. They can serve important roles in maintaining ecosystem equilibrium. For all these reasons and others, he urges fellow scientists to take a more neutral view of them and adopt well-established theoretical approaches for studying diseases on land to better understand how marine parasites operate. If scientists want to better predict when infections and infestations will recede, remain innocuous or spiral out of control, he says, they need to start thinking like parasites.