Intestinal Flukes Clinical Presentation

  • Author: Asim A Jani, MD, MPH, FACP; Chief Editor: Michael Stuart Bronze, MD   more...
 
Updated: Feb 14, 2011
 

History

Humans become infected with intestinal flukes by consuming contaminated food and water that consists of or contains the second intermediate hosts (eg, vegetation, snails, fish).

Most infected persons are asymptomatic and exhibit no physical signs.

Individuals with moderate infection present with occasional loose stools, some weight loss, malaise, and, occasionally, generalized abdominal pain.

Severe infection, in which toxic diarrhea alternating with constipation and hunger pangs are the first symptoms to appear, usually occurs near the end of the incubation period. As the infection progresses and the worm burden increases, edema of the face, abdominal wall, and lower limbs occurs, as well as ascites and generalized abdominal pain. Anorexia, nausea, and vomiting are also common. The diarrhea persists, becoming greenish-yellow and exceptionally malodorous.

In persons infected with H heterophyes, embolization of the eggs can lead to myocarditis, chronic heart failure, and/or cerebral emboli.

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Physical

In mild infections, patients are asymptomatic on physical examination.

In severe infections, patients are asthenic, with gray and harsh skin and edema of the face and lower extremities.

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Causes

Intestinal flukes are endemic in areas that contain abundant snail hosts (eg, China, Vietnam, India, other parts of Asia. Table 1. Common Intestinal Trematode Infections*

(Open Table in a new window)

InfectionSourceGeographic Distribution
FasciolopsiasisFreshwater plants (water caltrop, water chestnut)China, Thailand, Bangladesh, India
EchinostomiasisTadpoles, freshwater snails, fish, frogsIndonesia, Philippines, Taiwan, Thailand
HeterophyiasisFishEgypt, Iran, Tunisia, Turkey
MetagonimiasisFish (cyprinid)Far East, Spain, Eastern Europe
*Adapted with permission from Tribble D, Wagner KF. Trematode infections. Infectious Disease Practice. 1996;20:69-73.

Table 2. Commonly Associated Exposures and Clinical Features of Certain Intestinal Trematodes* (Open Table in a new window)

InfectionSourceClinical Features
Alaria americanaUndercooked frog legsDisseminated fatal thoracic, gastrointestinal, retroperitoneal, and CNS manifestations; intraocular infections
Echinostomiasis (16 species)Freshwater fish, aquatic plants, clams, snails, mollusks, contact with aquatic birdsMay be asymptomatic; mild abdominal pain, bloating, dyspepsia, diarrhea, eosinophilia
Fibricola speciesTadpolesAbdominal pain, diarrhea, fever, eosinophilia
Fasciolopsis speciesWater chestnut, water calthrop, water bamboo, water morning glory lotus and water hyacinthMay be symptomatic; may be subclinical; gastritis, nausea, diarrhea, eosinophilia; generalized edema in persons with heavy infection burden
Gastrodiscoides speciesVegetables, aquatic plantsOften asymptomatic; may manifest as abdominal pain and diarrhea in severe cases
Watsonius watsoniWater bambooSevere diarrhea
Fischoederius elongatesAquatic plantsEpigastric pain and vomiting
Heterophyes speciesMullets, fish; brackish waterMay be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss
Gymnophalloides seoiOystersFever, abdominal pain, anorexia, weight loss, diarrhea, pancreatitis
Carneophallus brevicaecaShrimpFatal when infection involves CNS and heart
Brachylaima ruminaePoultry, ratsAbdominal pain, diarrhea
Metagonimiasis speciesFish (ayu, golden carp)May be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss
Nanophyetus salmincolaUndercooked fish (eg, salmon, trout, steelhead)May be symptomatic; mild diarrhea, abdominal pain
*Adapted from Berger SA, Marr JS. Human Parasitic Diseases Sourcebook. 1st ed. Sudbury, MA: Jones and Bartlett; 2006.
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Contributor Information and Disclosures
Author

Asim A Jani, MD, MPH, FACP  Clinician-Educator and Epidemiologist, Consultant and Senior Physician, Florida Department of Health; Diplomate, Infectious Diseases, Internal Medicine and Preventive Medicine

Asim A Jani, MD, MPH, FACP is a member of the following medical societies: American Association of Public Health Physicians, American College of Physicians, American College of Preventive Medicine, American Medical Association, American Public Health Association, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Coauthor(s)

Chi Hiong U Go, MD  Assistant Professor, Department of Internal Medicine, Texas Tech University Health Science Center at Odessa

Chi Hiong U Go, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine

Disclosure: Nothing to disclose.

Paul Chen  University of Texas Southwestern Medical School

Disclosure: Nothing to disclose.

Burke A Cunha, MD  Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Specialty Editor Board

Thomas E Herchline, MD  Professor of Medicine, Wright State University, Boonshoft School of Medicine; Medical Director, Public Health, Dayton and Montgomery County, Ohio

Thomas E Herchline, MD is a member of the following medical societies: Alpha Omega Alpha, Infectious Diseases Society of America, and Infectious Diseases Society of Ohio

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Ronald A Greenfield, MD  Professor, Department of Internal Medicine, University of Oklahoma College of Medicine

Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology

Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubist Honoraria Speaking and teaching; Forest Pharmaceuticals Speaking and teaching

Eleftherios Mylonakis, MD  Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital

Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD  Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

Additional Contributors

The author would like to acknowledge Paul Chen, BS, ScM (2008) in Genetic Epidemiology, Johns Hopkins University Bloomberg School of Public Health, whose contributions and insights were invaluable for the revision of this article.

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Life cycle of Fasciolopsis buski. Image reproduced from the Division of Parasitic Disease, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
The life cycle of Fasciolopsis. Immature eggs are discharged into the intestine and stool and become embryonated in water. The eggs then release miracidia, which invade a suitable snail intermediate host, in which the parasites undergo several developmental stages (sporocysts, rediae, cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic plants, which are eaten by mammalian hosts (humans and pigs), who become infected. After ingestion, the metacercariae excyst in the duodenum and attach to the intestinal wall, where they develop into adult flukes (20-75 mm X 8-20 mm) in approximately 3 months and attach to the intestinal wall of the mammalian hosts. The adults have a life span of about one year. Image reproduced from the Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
Egg of Fasciolopsis buski. Images reproduced from the Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
Adult fluke of Fasciolopsis buski. Image reproduced from the Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
The life cycle of Heterophyes. The adult parasites release embryonated eggs (each with a fully developed miracidium), which are then passed in the host's feces. After ingestion by a suitable snail (first intermediate host), the eggs hatch and release miracidia, which penetrate the snail's intestine. Snails of the genera Cerithidea and Pirenella are important hosts in Asia and the Middle East, respectively. The miracidia undergo several developmental stages in the snail (sporocysts, rediae, cercariae). Many cercariae are produced from each redia. The cercariae are released from the snail and encyst as metacercariae in the tissues of a suitable freshwater or brackish-water fish (second intermediate host). The definitive host becomes infected by ingesting undercooked or salted fish that contains metacercariae. After ingestion, the metacercariae excyst, attach to the mucosa of the small intestine, and mature into adults (measuring 1-1.7 mm X 0.3-0.4 mm). Heterophyes heterophyes infects humans, various fish-eating mammals (eg, cats, dogs), and birds. Image reproduced from the Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
Life cycle of Metagonimus. The adult parasites release fully embryonated eggs (each with a fully developed miracidium), which are then passed in the host's feces. After ingestion by a suitable snail (first intermediate host), the eggs hatch and release miracidia, which penetrate the snail's intestine. Snails of the genus Semisulcospira are the most common intermediate host for Metagonimus yokogawai. The miracidia undergo several developmental stages in the snail (sporocysts, rediae, cercariae). Many cercariae are produced from each redia. The cercariae are released from the snail and encyst as metacercariae in the tissues of a suitable freshwater or brackish-water fish (second intermediate host). The definitive host becomes infected by ingesting undercooked or salted fish that contains metacercariae. After ingestion, the metacercariae excyst, attach to the mucosa of the small intestine, and mature into adults (measuring 1-2.5 mm X 0.4-0.75 mm). M yokogawai infects humans, fish-eating mammals (eg, cats, dogs), and birds. Image reproduced from the Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Ga.
Table 1
InfectionSourceGeographic Distribution
FasciolopsiasisFreshwater plants (water caltrop, water chestnut)China, Thailand, Bangladesh, India
EchinostomiasisTadpoles, freshwater snails, fish, frogsIndonesia, Philippines, Taiwan, Thailand
HeterophyiasisFishEgypt, Iran, Tunisia, Turkey
MetagonimiasisFish (cyprinid)Far East, Spain, Eastern Europe
*Adapted with permission from Tribble D, Wagner KF. Trematode infections. Infectious Disease Practice. 1996;20:69-73.
Table 2. Commonly Associated Exposures and Clinical Features of Certain Intestinal Trematodes*
InfectionSourceClinical Features
Alaria americanaUndercooked frog legsDisseminated fatal thoracic, gastrointestinal, retroperitoneal, and CNS manifestations; intraocular infections
Echinostomiasis (16 species)Freshwater fish, aquatic plants, clams, snails, mollusks, contact with aquatic birdsMay be asymptomatic; mild abdominal pain, bloating, dyspepsia, diarrhea, eosinophilia
Fibricola speciesTadpolesAbdominal pain, diarrhea, fever, eosinophilia
Fasciolopsis speciesWater chestnut, water calthrop, water bamboo, water morning glory lotus and water hyacinthMay be symptomatic; may be subclinical; gastritis, nausea, diarrhea, eosinophilia; generalized edema in persons with heavy infection burden
Gastrodiscoides speciesVegetables, aquatic plantsOften asymptomatic; may manifest as abdominal pain and diarrhea in severe cases
Watsonius watsoniWater bambooSevere diarrhea
Fischoederius elongatesAquatic plantsEpigastric pain and vomiting
Heterophyes speciesMullets, fish; brackish waterMay be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss
Gymnophalloides seoiOystersFever, abdominal pain, anorexia, weight loss, diarrhea, pancreatitis
Carneophallus brevicaecaShrimpFatal when infection involves CNS and heart
Brachylaima ruminaePoultry, ratsAbdominal pain, diarrhea
Metagonimiasis speciesFish (ayu, golden carp)May be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss
Nanophyetus salmincolaUndercooked fish (eg, salmon, trout, steelhead)May be symptomatic; mild diarrhea, abdominal pain
*Adapted from Berger SA, Marr JS. Human Parasitic Diseases Sourcebook. 1st ed. Sudbury, MA: Jones and Bartlett; 2006.
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