Fish tapeworm, or
The CDC states that humans get Diphyllobothrium most often by eating uncooked or undercooked fish, such as salmon, that is infected with tapeworm larvae. Once inside the host, the larvae then grow.
Four species of Pacific salmon, according to the study, are known to carry the Japanese tapeworm infections: chum salmon, masu salmon, pink salmon and sockeye salmon. The salmon are exported on ice -- fresh and unfrozen -- to restaurants worldwide. There was no mention in the study of infection in farm-raised salmon.
Despite their presence in human food, the worms in canned salmon are cooked and present little risk to humans eating them. “Even if someone ate a live parasite in a piece of raw salmon, humans are not the preferred host, so the parasite wouldn't survive,” Mastick said.
Most infections are asymptomatic. However symptoms can include abdominal discomfort, diarrhea, vomiting, and weight loss. Vitamin B12 deficiency leading to pernicious anemia may occur.
Those who prefer the safe side can stick with adequately frozen or cooked fish, according to the CDC. “Cooking for 145 Fahrenheit for four or five minutes will destroy the tapeworm,” said Okolo, who was also not involved in the study. “Freezing fish under certain conditions will also destroy the worm and its larvae.”
The chance of finding a worm in your salmon or sushi is very low, and while ingesting one can potentially lead to an infection, this doesn't happen very often. According to the FDA fewer than 10 cases are diagnosed in the U.S. every year, although many others may be unreported.
Cooking fish to an internal temperature of 140°F will kill all fish nematodes and tapeworms. Normal cooking procedures generally exceed this temperature.
Oshiro says worms are more often found in salmon because they spend part of the time in fresh water. He explained that typically farm raised salmon will not have worms. “If you are insisting on eating something raw, yeah make sure to stay away from from the wild caught salmon,” Oshiro explained.
It is in fact a highly unappealing substance called coagulated protein, or albumin. A lot of people think the white substance is fat and so try and wipe it away, but it's actually completely safe. As the fish cooks, albumin is pushed out of the muscle fibres before coagulating at the surface.
Worm parasites only cause health problems when inadequately prepared fish are eaten (proper freezing and normal cooking kill the worms). The worms are not passed from person to person. Swallowing a live parasitic worm may not cause any illness if it passes through the intestine and is excreted.
However, for consumers who catch fish fresh, most home freezers have temperatures at 0 to 10 degrees, which may not be cold enough to kill parasites because it can take up to 7 days at -4 degrees or below to kill parasites, especially in large fish, according to the FDA.
Fish tapeworm, or Diphyllobothrium spp, is acquired by eating raw or undercooked freshwater or anadromous fish (ie, sea fish that spawn in freshwater rivers, such as salmon).
More than 90% of some wild-caught fish is estimated to be infected with at least parasite eggs, while more than 75% of filets from wild-caught salmon contain parasitic worms.
These parasites are usually killed by cooking the fish to a temperature of at least 145°F for fifteen seconds. The Food Code and the Texas Food Establishment Rules require that fish that are to be consumed raw or undercooked be frozen at a temperature and time guaranteed to kill parasites.
If you really want to feast on fish but paranoia has now gotten the best of you, there is an at-home method you can try: fish candling. This method has you place a bright light beneath a fillet of fish so you can see the shadows of any worms present.
Early studies reported high levels of PCBs and other contaminants in farmed salmon – higher than in some species of wild salmon, such as pink salmon. Follow-up studies haven't confirmed this and the consensus among scientists and regulators is that farmed salmon and wild salmon are safe foods.
That white slimy stuff is called albumin, and it's actually just a harmless (albeit pretty gross-looking) protein that solidifies as salmon cooks.
Large tuna are considered parasite free and can be purchased raw without being frozen. Certain aquacultured fish, such as salmon, may also be parasite free. The supplier must stipulate in writing that the fish meets certain requirements that deem it free from parasites.
“In general, killing parasites requires freezing and storing fish at a surrounding temperature of minus 4 degrees Fahrenheit or colder for seven days; or freezing at a surrounding temperature of minus 31 degrees or colder until the fish is solid and storing at the same temperature for 15 hours; or freezing at a ...
Freezing mitigates the risk of human illness by inactivating parasites in fish that will be consumed raw or undercooked.
Freeze the fish at -31°F or below until solid AND store it at or below -4° F for at least 24 hours. Freezing requirements apply to aquacultured fish that are fed live feed. There is a reduced hazard of parasites in aquacultured fish raised under specific conditions.