It's hard to make the case for fish parasites (which yes, this article is going to do). For one thing, most people love eating fish; personally, I resisted when I was younger but succumbed as an adult. Fish are tasty, healthy, and can be prepared in a variety of ways.
More important, though, is the fact that most people hate parasites. And it's kind of hard not to, especially when there are stories like this one from The Washington Post in January floating around the internet:
It was a Monday in August last year when the man showed up in the emergency room of UCSF Fresno's Community Regional Medical Center clutching a plastic grocery bag and asking doctors to treat him for tapeworms — parasites that can invade the digestive tract of animals and humans. Banh said he didn't think too much of it; he had heard patients express similar concerns about tapeworms in the past.
Banh opened the sack.
Inside, he said, was a cardboard toilet paper tube — with a tapeworm wrapped around it.
Banh said the worm was dead when he saw it but noted the man told him “it was alive when he pulled it out and it was wiggling in his hand.” Banh stretched it out on the ER floor and measured it — all 5½ feet of it, he said in an interview Friday with The Washington Post.
“It got long enough that some of it was sneaking out of him,” he said about the parasite.
And yes — it is believed that the man in that story contracted the fish parasite by eating sashimi, another term for raw or undercooked fish.
"Animals get sick and carry pathogens, just like people, and there is an elevated risk of contracting a food-borne illness when eating raw meat or fish," Dr. Jillian Fry, Project Director of the Public Health & Sustainable Aquaculture Project at Johns Hopkins Bloomberg School of Public Health, told Salon. "Sensitive populations, like pregnant women and people with a compromised immune system, should avoid eating raw meat or fish for this reason. When consuming raw fish, consumers should eat at reputable businesses with good food handling practices."
She added, "The possibility of a tapeworm infection is very unappetizing, but it is not a reason to avoid eating fish; the current risk level is low and there are effective and safe treatments for tapeworms."
Fry's verdict was echoed in the abstract of a 2005 article in the journal Clinical Infectious Diseases called "Sushi Delights and Parasites: The Risk of Fishborne and Foodborne Parasitic Zoonoses in Asia," which warned that the growing popularity of Japanese cuisine carried with it certain unpleasant health risks:
Because of the worldwide popularization of Japanese cuisine, the traditional Japanese fish dishes sushi and sashimi that are served in Japanese restaurants and sushi bars have been suspected of causing fishborne parasitic zoonoses, especially anisakiasis. In addition, an array of freshwater and brackish-water fish and wild animal meats, which are important sources of infection with zoonotic parasites, are served as sushi and sashimi in rural areas of Japan. Such fishborne and foodborne parasitic zoonoses are also endemic in many Asian countries that have related traditional cooking styles. Despite the recent increase in the number of travelers to areas where these zoonoses are endemic, travelers and even infectious disease specialists are unaware of the risk of infection associated with eating exotic ethnic dishes.
In short: While stories like the fish parasite one from January are unappealing, to say the least, the reality is that we should not be concerned about there being too many parasites. We should be worried about how changes to our environment — and, specifically, global warming — might be causing an ecologically dangerous reduction in the number of parasites.
"Ironically, one of the very few 'positive' impacts of global warming could be a decrease in some of the most horror-inducing parasites like tapeworm," Michael E. Mann, a distinguished professor of atmospheric science at Penn State University, joked in an email to Salon. After referring me to a New York Times article from last year by Carl Zimmer, Mann said, "I’m being intentionally a bit glib here of course, because the demise of parasites in general could have larger negative ramifications for food webs and ecosystems."
He added, "Loss of species, in general, is not a good thing."
This notion was shared by Zimmer's article, which argued that "as much as a tapeworm or a blood fluke may disgust us, parasites are crucial to the world’s ecosystems. Their extinction may effect entire food webs, perhaps even harming human health." After detailing an extensive study led by University of California, Berkeley graduate student Colin J. Carlson on how global warming will impact parasite species, Zimmer described the impact that the mass extinction of various parasitic species may have on the planet (the study projected that roughly 30 percent of them could disappear).
Mr. Carlson said that climate change would do more than just drive some species extinct. Some parasites would move into new territory.
Deer ticks, for example, spread Lyme disease, and climate change models suggest they have a rosy future as they expand northward. “We’re not worried about them going extinct,” said Mr. Carlson.
Migrating parasites like these will arrive in ecosystems where other parasitic species are disappearing. With less competition, they may be able to wreak more havoc — and not just on animal hosts. Many human diseases are the result of parasites and pathogens jumping from animal species to our own.
“If parasites are keeping disease down in wildlife, they might also be indirectly keeping them down in humans,” Mr. Carlson said. “And we might lose that.”
There are two lessons that can be learned from these stories:
1. While you shouldn't shy away from exotic cuisines that you love out of fear, it is important to exercise caution about what you put into your body. Because raw and undercooked seafood can often be riddled with parasites, make sure that you do not eat those foods unless you know they are being sold by reputable stores, restaurants and other vendors.
2. Parasites, both those that come from fish and animals that live in other types of hosts, play an important role in our ecosystem. It is important to look at the planet beyond the interests of our own species and appreciate how even the most disgusting organisms can still be essential for its survival.
This last point doesn't mean that we have to like parasites. It just means we have to recognize that they are still important.
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