You have been logged out of VisualDx or your session has expired.

Please reload this page and sign into VisualDx to continue.

..
  VisualDx Mobile   Select Language

Get VisualDx Mobile

There are VisualDx mobile apps available for iOS and Android devices.

You will need a VisualDx account to use the mobile apps.



Already have an account? Sign In or
sign up for a free trial.

Users with VisualDx accounts earn CME credits for using VisualDx.

Already have an account? Sign In or
sign up for a free trial.

Create a Personal Account

E-mail (username)
Password
Verify Password
First Name
Last Name

Personal Account Created

Mobile Access

You can now download VisualDx for your iOS and Android devices. Launch the VisualDx app from your device and sign in using your VisualDx personal account username and password.

CME Certification

Sign in with your personal account to earn and claim CME credits through VisualDx. Credits can be earned by building a differential or looking up a diagnosis.

Version: 7.13.1441   (build df7aed4)
Select Language


Select Region

Send us your feedback

E-mail
Message
This field is required

Oops! There was an issue during submission. Please try again. If the problem persists, email feedback@visualdx.com with your feedback.

Thank You!

We appreciate your feedback and you will be hearing from us soon.

OK

Share This Page

Thank You!

We have sent an e-mail with a link to the current page.

OK

E-mail This Patient Information Sheet

Thank You!

We have sent an e-mail with this patient information.

OK

Image Contributors

Individuals

  • Christine Ahn MD
    Carl Allen DDS, MSD
    Brandon Ayres MD
    Howard P. Baden MD
    Robert Baran MD
    Keira Barr MD
    Gregory J. Basura MD, Ph.D
    Donald Belsito MD
    Jeffrey D. Bernhard MD
    Jesse Berry MD
    Victor Blanco MD
    Benjamin R. Bohaty MD
    William Bonnez MD
    Sarah Brenner MD
    Robert A. Briggaman MD
    Robert Brodell MD
    Roman Bronfenbrener MD
    Walter Brooks MD
    William Buckley MD
    Philip Bulterys MD, PhD (candidate)
    Susan Burgin MD
    Sonya Burton MD
    Sean P. Bush MD, FACEP
    Jeffrey Callen MD
    Scott Camazine MD
    Michael Cardwell
    Shelley D. Cathcart MD
    Robert Chalmers MD, MRCP, FRCP
    Chia-Yu Chu MD, PhD
    Flavio Ciferri MD
    Maria Rosa Cordisco MD
    Noah Craft MD, PhD
    John T. Crissey MD
    Harold E. Cross MD, PhD
    Charles E. Crutchfield III MD
    Adriana Cruz MD
    Donna Culton MD, PhD
    Bart J. Currie MBBS, FRACP, DTM&H
    Chicky Dadlani MD
    Alexander Dane DO
    C. Ralph Daniel III MD
    Thomas Darling MD, PhD
    William Delaney MD
    Damian P. DiCostanzo MD
    Ncoza Dlova MD
    James Earls MD
    Libby Edwards MD
    Melissa K. Egge MD
    Charles N. Ellis MD
    Rachel Ellis MD
    David Elpern MD
    Nancy Esterly MD
    Stephen Estes MD
    E. Dale Everett MD
    Janet Fairley MD
    David Feingold MD
    Jennifer J. Findeis-Hosey MD
    Benjamin Fisher MD
    Henry Foong MBBS, FRCP
    David Foster MD, MPH
    Brian D. Foy PhD
    Michael Franzblau MD
    Vincent Fulginiti MD
    Sunir J. Garg MD, FACS
    Kevin J. Geary MD
    Lowell Goldsmith MD, MPH
    Sethuraman Gomathy MD
    Bernardo Gontijo MD, PhD
    Kenneth Greer MD
    Kenneth G. Gross MD
    Alan Gruber MD
    Nathan D. Gundacker MD
    Akshya Gupta MD
    Vidal Haddad MSC, PhD, MD
    Edward Halperin MD, MA
    Ronald Hansen MD
    John Harvey
    Rizwan Hassan MD
    Michael Hawke MD
    Jason E. Hawkes MD
    Peter W. Heald MD
    David G. Hicks MD
    Sarah Hocker DO
    Ryan J. Hoefen MD, PhD
    Li-Yang Hsu MD
    William Huang MD
    Sanjana Iyengar MD
    Alvin H. Jacobs MD
    Saagar Jadeja MD
    Shahbaz A. Janjua MD
    Joshua J. Jarvis MD
    Kit Johnson
    Zachary John Jones MD
    Robert Kalb MD
    A. Paul Kelly MD
    Henry Kempe MD
    Loren Ketai MD
    Sidney Klaus MD
    Ashwin Kosambia MD
    Jessica A. Kozel MD
    Carl Krucke
    Mario E. Lacouture MD
    Joseph Lam MD
    Alfred T. Lane MD
    Edith Lederman MD
    Nahyoung Grace Lee MD
    Pedro Legua MD, PhD
    Robert Levin MD
    Bethany Lewis MD
    Sue Lewis-Jones FRCP, FRCPCH
    Taisheng Li MD
    Christine Liang MD
    Shari Lipner MD, PhD
    Adam Lipworth MD
    Jason Maguire MD
    Mark Malek MD, MPH
    Jere Mammino DO
    Ricardo Mandojana MD
    Lynne Margesson MD
    Thomas J. Marrie MD
    Maydel Martinez MD
    Ralph Massey MD
    Patrick McCleskey MD
    Karen McKoy MD
    Thomas McMeekin MD
    Josette McMichael MD
    Somchai Meesiri MD
    Joseph F. Merola MD
    Mary Gail Mercurio MD
    Anis Miladi MD
    Larry E. Millikan MD
    Dan Milner Jr. MD
    Zaw Min MD
    Stephanie Montero
    Alastair Moore MD
    Keith Morley MD
    Dean Morrell MD
    Samuel Moschella MD
    Rehan Naseemuddin MD
    Taimor Nawaz MD
    Vic Newcomer MD
    John Nguyen MD
    Matilda Nicholas MD
    Thomas P. Nigra MD
    Steven Oberlender MD, PhD
    Maria Teresa Ochoa MD
    Art Papier MD
    Lawrence Parish MD
    Tanner Parrent MD
    Mukesh Patel MD
    Lauren Patty-Daskivich MD
    David Peng MD, MPH
    Robert Penne MD
    Nitipong Permpalung MD
    Miriam Pomeranz MD
    Doug Powell MD
    Harold S. Rabinovitz MD
    Christopher J. Rapuano MD
    Sireesha Reddy MD
    Angela Restrepo MD, PhD
    Bertrand Richert MD, PhD
    J. Martin Rodriguez, MD, FACP
    Theodore Rosen MD
    Misha Rosenbach MD
    Scott Schiffman MD
    Robert H. Schosser MD
    Glynis A. Scott MD
    Carlos Seas MD, MSc
    Deniz Seçkin MD
    Daniel Sexton MD
    Paul K. Shitabata MD
    Tor Shwayder MD, FAAP, FAAD
    Elaine Siegfried MD
    Gene Sienkiewicz MD
    Christye Sisson
    Philip I. Song MD
    Mary J. Spencer MD, FAAP
    Lawrence B. Stack MD
    Sarah Stein MD
    William Van Stoecker MD
    Frances J. Storrs MD
    Erik J. Stratman MD
    Lindsay C. Strowd MD
    Erika Summers MD
    Belinda Tan MD, PhD
    Robert Tomsick MD
    Hensin Tsao MD, PhD
    Richard P. Usatine MD
    Jenny Valverde MD
    Vishalakshi Viswanath MD
    Susan Voci MD
    Lisa Wallin ANP, FCCWS
    Douglas Walsh MD
    Ryan R. Walsh MD
    George Watt MD
    Clayton E. Wheeler MD
    Sally-Ann Whelan MS, NP, CWOCN
    Jan Willems MD, PhD
    James Henry Willig MD, MPH
    Karen Wiss MD
    Vivian Wong MD, PhD
    Sook-Bin Woo MS, DMD, MMSc
    Jamie Woodcock MD
    Stephen J. Xenias MD
    Nathaniel Yohannes
    Lisa Zaba MD
    Vijay Zawar MD
    Bonnnie Zhang MD
    Carolyn Ziemer MD
    Jeffrey P. Zwerner MD, PhD


Organizations

  • Am. Journal of Trop. Med & Hygiene
  • Armed Forces Pest Management Board
  • Blackwell Publishing
  • Bugwood Network
  • Centers For Disease Control and Prevention
  • Centro Internacional de Entrenamiento e Investigaciones Mèdicas (CIDEIM)
  • Dermatology Online Journal
  • East Carolina University (ECU), Division of Dermatology
  • International Atomic Energy Agency
  • Massachusetts Medical Society
  • Oxford University Press
  • Radiological Society of North America
  • Washington Hospital Center
  • Wikipedia
  • World Health Organization
ContentsSynopsisCodesLook ForDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsManagement PearlsTherapyReferences
Nanophyetiasis
Print
Other Resources UpToDate PubMed

Nanophyetiasis

Print Images (1)
Contributors: Zaw Min MD, FACP, James H. Willig MD, MSPH
Other Resources UpToDate PubMed

Synopsis

Nanophyetiasis is caused by the digenetic intestinal trematode Nanophyetus salmincola, a fish-borne parasite belonging to the family Troglotrematidae. Human infection with this intestinal fluke has been mainly reported from the coastal region of the Pacific Northwest of the United States. It is usually acquired by ingesting raw or undercooked freshwater parasite-infested salmonid fish (Pacific salmon), steelhead trout, or steelhead eggs. Cases of human infection acquired after handling of infected Pacific salmon fish have been reported.

The life cycle of N. salmincola requires 3 hosts: 2 intermediate hosts and 1 definite host. The eggs of N. salmincola are passed in the stool and hatch into larvae called miracidia, which penetrate and infect snails (the first intermediate host) commonly found in the Northwest. Within these snails, larvae mature into cercariae that leave the snails and infect and encyst in the flesh of salmonid fishes or non-salmonid fishes (the second intermediate host). Those infected fishes are ingested in raw or partially cooked fish by the definitive hosts, which include dogs and humans. Once in the human host, there is an incubation period of 1-15 weeks before clinical symptoms appear.

Dogs are typically infected by feeding off the remains of fresh fish or eating dead salmon on riverbanks. This trematode worm is not known to cause clinical disease in dogs, but it carries a rickettsial bacteria known as Neorickettsia helminthoeca, which is mostly known for its association with "salmon poisoning disease" in canids, a fatal disease if left untreated. However, there are no known reported cases of human infection by this rickettsial organism.

Human nanophyetiasis usually manifests 1 week after ingestion of infected fish or 1 month after handling fresh fish. Clinical manifestations are usually nonspecific and include fatigue, abdominal discomfort, nausea, vomiting with diarrhea, and weight loss. Asymptomatic infections are common. The first human case of nanophyetiasis was reported in 1956 when a researcher experimentally infected himself; this was followed by the first report of human intestinal infection with N. salmincola from eating infected salmonid fish in Washington State in 1987. Two years later, a case series of an additional 10 patients with nanophyetiasis was reported from the same geographic region. Interestingly, a biological technician was infected with N. salmincola after he necropsied more than a thousand fresh-killed coho salmon without protective gloves in Washington State. Accidental hand-to-mouth transmission occurred during this handling, and symptoms typical of nanophyetiasis started after 1 month. Additional evidence of human nanophyetiasis reported in the literature is sparse and has been lacking since 1990. It is likely to be underreported given its nonspecific symptoms and because it does not result in long-term morbidity and mortality.

Of note, another subspecies of Nanophyetus, known as Nanophyetus schikhobalowi, has reportedly been endemic in Eastern Siberia since 1931 with similar clinical features as its counterpart N. salmincola.

Peripheral eosinophilia (>500/µL) is a significant laboratory finding seen in up to 50% of the patients. Stool examination typically shows light brown eggs with a characteristic operculum at one end and a small blunt point at the other. The eggs are usually first detected in stool approximately 1 week after ingestion of infected fish.

There are as of yet no reported cases of mortality from human nanophyetiasis. All patients treated with an anti-helminth responded well and were cured. Reportedly, one-third of patients with positive stool examination were asymptomatic, which suggests that a significant proportion of infected individuals may go undiagnosed.

Codes

ICD10CM:
B66.8 – Other specified fluke infections

SNOMEDCT:
417627005 – Disease due to nanophyetidae

Look For

Subscription Required

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

With widespread worldwide popularization of traditional Japanese fish dishes (sushi and sashimi), the primary differential diagnoses are fish-borne parasitic zoonoses:
  • Diphyllobothriasis – Caused by the fish tapeworm Diphyllobothrium latum. Sources of human infection are salmon and lake trout. GI symptoms are usually absent, except the adult worms sometimes protrude from the anus. Its infestation is known to be associated with vitamin B12 deficiency and anemia. No peripheral eosinophilia is noted. The diagnosis is based on the detection of ova or proglottids in the feces. Treatment of choice is a single dose of praziquantel (10-20 mg/kg).
  • Anisakiasis – Caused by infection with either the herring worm (Anisakis simplex) or the cod worm (Pseudoterranova decipiens). Human infection is acquired through ingestion of raw or undercooked marine fish. There are several different clinical presentations depending on the type. Gastric anisakiasis usually presents as acute abdominal pain, nausea, and vomiting within a few minutes to hours after ingestion of infected fish. Diagnosis is confirmed by direct visualization of the parasite in the stomach during upper GI endoscopy, and treatment – removal of the worm – is performed immediately. Intestinal anisakiasis mimics symptoms of acute intestinal obstruction by mucosal and intestinal wall thickening. The larvae only survive a few days in the human intestinal tract, and so decompression with a nasogastric tube is usually the only treatment needed. Rarely, there are reported cases of extraintestinal anisakiasis causing eosinophilic granuloma in other visceral organs, usually accompanied by systemic allergic reactions such as angioedema, urticaria, and peripheral eosinophilia. Serodiagnosis could be performed by the antigen-capture ELISA test with high (near 100%) sensitivity and specificity. Albendazole (400 or 800 mg for 1-3 weeks) has been regarded as an effective therapy.
  • Intestinal capillariasis – Caused by the nematode Capillaria philippinensis. Human infection occurs after ingestion of raw freshwater or brackish-water fish. It is endemic in Southeast Asia (especially the Philippines and Thailand), and sporadic cases have been reported in various regions (eg, Japan, South Korea, Taiwan, India, Egypt, Iran). Symptoms are varied, from abdominal pain and diarrhea to progressive weight loss, anorexia, cachexia, and death if left untreated. No peripheral eosinophilia is noted. Diagnosis is confirmed by the detection of eggs on stool specimens. Standard therapy is albendazole 200 mg once daily for 10 days.
  • Paragonimiasis – Caused by infection with Paragonimus lung flukes. Paragonimus westermani is the most common species of human infection in Asia. The source of infection is freshwater crabs. The larvae migrate through the peritoneal cavity and diaphragm to the pleural space and finally reach the lung parenchyma, where solid worm cysts are formed. GI symptoms are usually absent. Typical manifestations are fever, chronic cough, and hemoptysis. Diagnosis is confirmed by chest radiographic findings of nodular or cavitary lesions, along with detection of ova in the sputum, stool, or gastric aspirates. Patients are usually treated with high-dose praziquantel 75 mg/kg/day for 3 days.
  • GnathostomiasisGnathostoma spinigerum is the major causal nematode of the disease in Asia, Latin America, and Africa. Infection occurs due to ingestion of undercooked freshwater fish, frogs, or snakes. Gnathostomiasis typically manifests as migratory skin lesions and peripheral eosinophilia. GI symptoms are typically absent. When larvae migrate to the central nervous system (CNS), fatal eosinophilic meningoencephalitis may result. For cutaneous lesions, either albendazole (400 mg daily or twice daily for 21 days) or ivermectin (0.2 mg/kg once) is effective. A combination of albendazole and corticosteroid therapy is recommended in patients with CNS disease.
  • Angiostrongyliasis – Human infection is caused by the nematode Angiostrongylus cantonensis and occurs after ingestion of raw shellfish, snails, or slugs. The majority of human cases are reported in the South Pacific islands and Southeast Asia. It is another important cause of eosinophilic meningoencephalitis in endemic regions. Its treatment is controversial, and some authors recommend a combined albendazole and corticosteroid therapy.

Best Tests

Subscription Required

Management Pearls

Subscription Required

Therapy

Subscription Required

References

Subscription Required

Last Updated: 05/29/2014
Copyright © 2018 VisualDx®. All rights reserved.
Nanophyetiasis
Print 1 Images
Nanophyetiasis : Abdominal pain, Diarrhea, Fatigue, Nausea, Vomiting, Weight loss, Bloating, EOS increased
Copyright © 2018 VisualDx®. All rights reserved.