(CNN) If you eat raw or undercooked fish, you risk developing an infection from parasites. 
 
 One of the most gruesome is tapeworm, a species of digestive tract-invading parasites that includes Diphyllobothrium nihonkaiense, or the Japanese broad tapeworm. 
 
 Though this worm was commonly believed to infect only fish in Asia, a study published Wednesday in the Centers for Disease Control and Prevention's monthly journal Emerging Infectious Diseases says wild salmon caught in Alaska had also been infected by this parasite. 
 
 Based on those results, researchers warn that salmon caught anywhere along the Pacific coast of North America may be infected. 
 
 Meet the tapeworm 
 
 The most common fish tapeworm is Diphyllobothrium latum. In 1986, scientists identified another member of this family, the Japanese broad tapeworm, and believed it had been responsible for about 2,000 infections reported to that point, making it the second most common cause of tapeworm infection. 
 
 However, continuing to study the tapeworms using new molecular methods, researchers funded by the Czech Science Foundation discovered they'd been wrong. 
 
 Almost all of the previous cases of tapeworm infections occurring in Japan, South Korea and the Pacific coast of Russia had actually been caused by Japanese tapeworms rather than D. latum. In fact, Japanese tapeworm larvae, known as plerocercoids, could be found in salmon caught off the coasts of eastern Russia and Japan. 
 
 Could Japanese tapeworms also be infecting salmon caught in the United States? 
 
 In July 2013, a team of scientists examined 64 wild Alaskan salmon. After filleting the musculature into narrow slices, the scientists observed these and the internal organs of each fish under a magnifying glass. 
 
 They discovered larvae, between 8 and 15 millimeters long, that continually elongated and contracted (as worms are known to do). With gene sequencing, they were identified as Japanese tapeworms. 
 
 Based on the study results, four species of Pacific salmon are known to carry Japanese tapeworm infections: chum salmon, masu salmon, pink salmon and sockeye salmon. Because these salmon are exported on ice -- unfrozen -- and then appear in restaurants around the world, infections caused by the Japanese tapeworm may occur anywhere, from China to Europe, from New Zealand to Ohio. 
 
 Few have symptoms 
 
 Compared with an infection resulting from D. latum, "we think this Japanese version would not be any different, although very little is actually known about this variant of tapeworms," said Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University School of Medicine who was not involved in the new study. 
 
 Because the Japanese version is from the same family of tapeworms, illness and symptoms should be largely the same, he said. 
 
 But D. latum and related species (including the Japanese tapeworm) can grow up to 30 feet long, according to the CDC 
 
 "Actually, most of the people who are infected don't have symptoms," Schaffner said. Some feel a little bit of abdominal discomfort, some have nausea or loose stools, and some even lose a little weight. 
 
 Most often, tapeworm leads to only minor symptoms, but in exceptional cases the infection can turn into a serious medical problem, according to Roman Kuchta, lead author of the study and a research scientist at the Academy of Sciences of the Czech Republic. 
 
 "Massive infections may result in intestinal obstruction" and painful inflammation of the bile ducts, said Kuchta. "The infections can have a substantial emotional impact on patients and their families, because segments are evacuated over a long period of time. More severe cases may require specialized consultations and complementary analyses, which are costly." 
 
 Along with emotional impact and expenses, there's also the initial shock -- terror, really -- of discovery. 
 
 "The reason you know you have tapeworms is you look in your stool and you find bits of tapeworm floating in the water -- and that usually panics you enormously," Schaffner said. After all, tapeworm infection is very unusual in the United States. 
 
 After discovering that you're infected, you can collect a sample from your toilet bowl and send it to a lab for testing, and then, with your doctor's help, the tapeworm can be identified and "treated very effectively," Schaffner said. 
 
 According to Dr. Patrick Okolo, chief of gastroenterology at Lenox Hill Hospital in New York, the medications used are not typical antibiotics but specialized drugs targeting specific types of parasites. 
 
 Though the study suggests that infections by Japanese tapeworm may be much more common in the US than anticipated, there's still "no evidence at all about how common it is," Schaffner said. 
 
 "Is this a teeny-tiny proportion of the population, or is this something the average family doctor better learn about?" he asked. 
 
 Other options: cooking or freezing 
 
 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." 
 
 Schaffner admits the new study has given him "a little bit of pause -- because I like salmon sushi." 
 
 He said talk of "emerging infections" or new infections comes about, in part, because new scientific methods are able to identify them. 
 
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 This view is supported by Jayde Ferguson, a co-author of the new study and a scientist at Alaska Department of Fish and Game. 
 
 "The tapeworm itself is probably not new -- it's just that more skilled parasitologist started looking for it. Identifying these parasites is challenging," said Ferguson. "This was simply a more detailed evaluation of the Diphyllobothrium that has occurred here for over a millennium." 
 
 Still, there's another important reason "old" infections from one part of the globe emerge as "new" infections on another part of the globe, said Schaffner. 
 
 "Because we do things that we haven't done before," Schaffner said. "Now, we have these fresh caught fish that can be transported anywhere and eaten raw. ... I am sure we will be on the lookout for this kind of tapeworm going forward." ||||| Japanese tapeworm found in Alaskan-caught salmon 
 
 Here's the gross news first: A tapeworm found in fish from Asia has now been found in Alaskan salmon. 
 
 The Centers for Disease Control recently posted an article in its Emerging Infectious Disease journal, stating that Diphyllobothrium nihonkaiense has been found in wild pink salmon from Alaska. Due to that reason, the CDC wrote that "salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw." 
 
 (Pair that info with the nightmare fact that tapeworms can grow up to 30 feet long, according to the CDC.) 
 
 The good news, however, is that this doesn't necessarily mean you need to swear off salmon sashimi completely. On the upside, the FDA really is here to protect you: As the Seattle Times points out, all raw fish served and sold in the United States is frozen — according to FDA standards — in order to kill parasites such as this new one mentioned. 
 
 Jayde Ferguson, co-author of the study and fish pathologist with the Department of Fish and Game, confirmed there isn't much concern with eating raw salmon in a restaurant, other than the usual concerns about eating uncooked seafood. 
 
 "If it was anything that was of concern, increased risk or anything like that from a management standpoint, we would have said something," Ferguson told the Alaska Dispatch News. "They're wild animals — they're going to have parasites, they're out in nature." 
 
 There is some concern in regards to those who have caught the fish themselves or have bought it freshly caught from someone else, and want to eat their salmon raw — in those instances, consumers should freeze their fish first, for at least a few days. 
 
 Unfortunately, there aren't many surefire signs that you have a tapeworm, CNN stated. Like other tapeworms, the symptoms could include abdominal pains, nausea, loose stools and weight loss. Once the tapeworm is identified, however, it can be effectively treated. 
 
 If this all sounds too gross for you, and you would rather be extra cautious, you can also cook your salmon at 145 degrees Fahrenheit for four or five minutes to destroy the tapeworm. ||||| When it comes to consumers, commercial sushi and ceviche — what you'd order in a restaurant or grocery store — shouldn't be a problem. The Alaska Food Code requires businesses to freeze fish before serving in order to control the parasite hazard, Stryker said. It's recommended that people who want to eat raw or undercooked fish that they've caught themselves (or bought fresh) should freeze their fish first for the same reason. ||||| Volume 23, Number 2—February 2017 
 
 Research Letter 
 
 Diphyllobothrium nihonkaiense Tapeworm Larvae in Salmon from North America 
 
 Roman Kuchta , Mikuláš Oros, Jayde Ferguson, and Tomáš Scholz 
 
 Author affiliations: Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic (R. Kuchta, T. Scholz) ; Slovak Academy of Sciences, Košice, Slovak Republic (M. Oros) ; State of Alaska Department of Fish and Game, Anchorage, Alaska, USA (J. Ferguson) 
 
 Cite This Article 
 
 Abstract Diphyllobothriosis is reemerging because of global importation and increased popularity of eating raw fish. We detected Diphyllobothrium nihonkaiense plerocercoids in the musculature of wild pink salmon (Oncorhynchus gorbuscha) from Alaska, USA. Therefore, salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw. 
 
 The Japanese broad tapeworm, Diphyllobothrium nihonkaiense (Yamane, Kamo, Bylund et Wikgren, 1986) (Cestoda: Diphyllobothriidea) is the second most common causative agent of diphyllobothriosis in humans; ≈2,000 cases have been reported, mainly from northeastern Asia (1). However, recent studies that used molecular methods indicate that the number of human cases caused by this tapeworm may have been highly underestimated (1). In addition, increasing popularity of eating raw fish is probably responsible for the increased number of imported cases in regions where this infection is not endemic (1). 
 
 In 1986, the Japanese broad tapeworm was recognized as a human parasite separate from the most common broad fish tapeworm, Diphyllobothrium latum, in Japan (2). The validity of the Japanese broad tapeworm was later confirmed by molecular data, especially the cox1 gene sequences (1). Evidence indicates that virtually all previous cases of diphyllobothriosis in humans in Japan, South Korea, and the Pacific coast of Russia that were attributed to D. latum tapeworms were caused by D. nihonkaiense tapeworms (1,3). Moreover, D. klebanovskii (Muratov et Posokhov, 1988) from the Pacific coast of Russia was recently synonymized with the Japanese broad tapeworm (1,4). 
 
 Studies on the transmission of the Japanese broad tapeworm in Japan and eastern Russia (Primorsky Region) have identified 4 species of Pacific salmon as the principal sources of human infection: chum salmon (Oncorhynchus keta), masu salmon (O. masou), pink salmon (O. gorbuscha), and sockeye salmon (O. nerka). These anadromous fish become infected in brackish water along the coast of the North Pacific Ocean (1,5). Tapeworm larvae infective for humans (plerocercoids) have been described in only a few studies performed in eastern Russia and Japan, (e.g., as plerocercoids type F from the musculature of chum salmon in Kamchatka, Russia) (2,6,7). 
 
 For decades, the possible occurrence of the Japanese broad tapeworm on the Pacific coast of North America was ignored, but since 2008, human infection with adult tapeworms and natural infection of carnivores (wolves and bears) with adult tapeworms have been confirmed by use of molecular markers (1,8–10). We report finding Japanese broad tapeworm plerocercoids in North America. Our main intent is to alert parasitologists and medical doctors about the potential danger of human infection with this long tapeworm resulting from consumption of infected salmon imported (on ice) from the Pacific coast of North America and elsewhere. 
 
 Figure 
 
 Video 
 
 In July 2013, we examined 64 wild Pacific salmon of 5 species:1 chinook salmon (O. tshawytscha), 1 coho salmon (O. kisutch), 23 pink salmon, 8 rainbow trout (O. mykiss), and 31 sockeye salmon in south-central Alaska, USA. The salmon were collected by angling (under permit no. SF2013–218) or obtained from local fishermen. The musculature was filleted to narrow slices, and internal organs were observed under a magnifying glass. Several morphotypes of diphyllobothriid plerocercoids were found, including a single larva in the musculature of pink salmon collected in Resurrection Creek (near Hope, Alaska). This plerocercoid, which was later identified as that of the D. nihonkaiense tapeworm, was found unencysted, deep in the musculature of the anterior part of the fish, near the spinal cord (Figure). It was highly motile, had a retracting scolex, and was 8–15 mm long, depending on the state of elongation or contraction (Figure; Video). After fixation with hot water, the plerocercoid was 10 mm long, had an elongate scolex 1.05 mm long and 0.60 mm wide, and possessed 2 narrow bothria opened on the apical end (Figure). The sequences of the cox1 and 28S rRNA genes (lsrDNA) were almost identical to those of the Japanese broad tapeworm available in the GenBank database (sequence similarities of 99% [GenBank accession no. KY000483] and 100% [KY000484], respectively), thus providing unequivocal support that this plerocercoid was a larva of the D. nihonkaiense tapeworm reported from North America. 
 
 This report provides additional evidence that salmon from the Pacific coast of North America may represent a source of human infection. Because Pacific salmon are frequently exported unfrozen, on ice, plerocercoids may survive transport and cause human infections in areas where they are not endemic, such as China, Europe, New Zealand, and middle and eastern United States (1). It is probable that most diphyllobothriosis cases originally attributed to D. latum may have been caused by D. nihonkaiense tapeworms. For more effective control of this human foodborne parasite, detection of the sources of human infection (i.e., host associations), and critical revision of the current knowledge of the distribution and transmission patterns of individual human-infecting tapeworms are needed. 
 
 Dr. Kuchta is a researcher at the Institute of Parasitology, Czech Academy of Sciences. His research interests include biology, phylogeny, and molecular diagnosis of parasitic helminths, mainly those that cause diphyllobothriosis and sparganosis. 
 
 Acknowledgments 
 
 We thank Jan Brabec for the new sequences of studied material. This work was supported by the Czech Science Foundation (grant no. P506/12/1632); the Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic (RVO: 60077344); the Grant Agency VEGA (no. 2/0159/16); and the Slovak Research and Development Agency (no. APVV-15-0004). 
 
 References 
 
 Kuchta R , Scholz T , Brabec J , Narduzzi-Wicht B . Diphyllobothrium, Diplogonoporus and Spirometra. In: Xiao L, Ryan U, Feng F, editors. Biology of Foodborne Parasites Section III. Important Foodborne Helminths. Boca Raton (FL): CRC Press; 2015 . p. 299–326. Yamane Y , Kamo H , Bylund G , Wikgren BJP . Diphyllobothrium nihonkaiense sp. nov. (Cestoda: Diphyllobothriidae): revised identification of Japanese broad tapeworm. Shimane J Med Sci . 1986 ; 10 : 29 – 48 . Choi S , Cho J , Jung B-K , Kim D-G , Jeon SJ , Jeon H-K , et al. Diphyllobothrium nihonkaiense: wide egg size variation in 32 molecularly confirmed adult specimens from Korea. Parasitol Res . 2015 ; 114 : 2129 – 34 . DOI PubMed Arizono N , Shedko M , Yamada M , Uchikawa R , Tegoshi T , Takeda K , et al. Mitochondrial DNA divergence in populations of the tapeworm Diphyllobothrium nihonkaiense and its phylogenetic relationship with Diphyllobothrium klebanovskii. Parasitol Int . 2009 ; 58 : 22 – 8 . DOI PubMed Muratov IV . [A new type of diphyllobothriasis foci in the Far East] . Med Parazitol (Mosk) . 1992 ; 61 : 25 – 7 . PubMed Gorman-Kadoshnikov PB , Chizhova TP , Iakovleva TA . [A new type of Diphyllobothria plerocercoids from salmon of Kamchatka] . Med Parazitol (Mosk) . 1970 ; 39 : 237 – 9 . PubMed Dovgalev AS , Valovaya MA , Piskunova YA , Romanenko NA , Khobakova VI , Artamoshin AS . The morphology of human diphyllobothriasis agent in the Far East . Med Parazitol (Mosk) . 1991 ; 60 : 42 – 6 . PubMed Bryan HM , Darimont CT , Hill JE , Paquet PC , Thompson RC , Wagner B , et al. Seasonal and biogeographical patterns of gastrointestinal parasites in large carnivores: wolves in a coastal archipelago. Parasitology . 2012 ; 139 : 781 – 90 . DOI PubMed Catalano S , Lejeune M , Tizzani P , Verocai GG , Schwantje H , Nelson C , et al. Helminths of grizzly bears (Ursus arctos) and American black bears (Ursus americanus) in Alberta and British Columbia, Canada. Can J Zool . 2015 ; 93 : 765 – 72 . DOI Fang FC , Billman ZP , Wallis CK , Abbott AN , Olson JC , Dhanireddy S , et al. Human Diphyllobothrium nihonkaiense infection in Washington State. J Clin Microbiol . 2015 ; 53 : 1355 – 7 . DOI PubMed 
 
 Figures 
 
 Table of Contents – Volume 23, Number 2—February 2017
– It turns out that a parasite thought to be confined to fish from Asia is in fish around the US, too. Researchers identified the Japanese broad tapeworm, aka Diphyllobothrium nihonkaiense, in wild pink salmon caught off Alaska, they report in a study in the CDC's Emerging Infectious Diseases journal. "Therefore, salmon from the American and Asian Pacific coasts and elsewhere pose potential dangers for persons who eat these fish raw," write the researchers. However, Jayde Ferguson, a state wildlife official who co-authored the study, tells Alaska Dispatch News that the discovery shouldn't be much cause for alarm among consumers. "If it was anything that was of concern, increased risk or anything like that from a management standpoint, we would have said something," he says. "They're wild animals—they're going to have parasites, they're out in nature." The comfort for US sushi lovers is that the FDA requires that any fish sold or served raw be frozen first, which would kill any parasites, reports the Seattle Times. (Those who caught the fish themselves and planned to eat it raw would want to freeze it first as well, notes the San Francisco Chronicle.) The researchers cautioned that "Pacific salmon are frequently exported unfrozen," though that doesn't apply to the vast majority of Alaskan salmon. A preventive medicine professor at Vanderbilt University School of Medicine tells CNN most infected humans remain asymptomatic—some may feel slight abdominal discomfort or nausea—though there are rare cases in which the infection can turn serious. The CDC notes that cooking the fish also will annihilate Diphyllobothrium parasites. (A Canadian man bit into a piece of salmon and fell into a coma.)