Intestinal Flukes Follow-up
- Author: Joseph Adrian L Buensalido, MD; Chief Editor: Michael Stuart Bronze, MD more...
Further Outpatient Care
Health education is essential; proper washing and thorough cooking of vegetables or fish are essential to prevent egg ingestion.
Further Inpatient Care
Antispasmodics may relieve abdominal pain.
Iron supplements may be used to treat anemia, which may require transfusions in severe cases.
Vitamin C (ascorbic acid) may be administered to facilitate iron absorption.
Eliminating the intermediate host snail is the key to controlling infection with intestinal flukes.
Proper cleaning and processing of raw vegetables by immersing in boiling water for a few seconds, followed by peeling and washing in clean water, is important in preventing infection with intestinal flukes, especially in endemic areas.
Night soil (human excreta) and pig excreta should not be used as fertilizers.
Metacercariae are not necessarily inhibited or destroyed by interventions such as smoking or freezing; and the practice of fish pickling is ineffective. Irradiation practices may be of benefit in managing the burden of metacercariae in the process of food preparation.
Many strategies to control opisthorchiasis have been used in Thailand. The strategies include mass drug administration and education to decrease the consumption of raw fish. Over the last decade, these methods have changed the epidemiology of O viverrini infection in Thailand. In the past, O viverrini infections were characterized as heavy infections that were concentrated in particular villages. Now, because of these strategies, O viverrini infections have become "lighter" but more widespread in terms of geographic distribution.
Parasitic helminths reside in immunologically exposed extracellular locations within their hosts, yet they are capable of surviving for extended periods. To enable this survival, these parasites have developed complex and multifaceted mechanisms to subvert or suppress host immunity. There are studies on the immunomodulation by helminth parasites of ruminants and the parasite-derived molecules involved in driving this modulation. Such immunomodulatory molecules have considerable promise as vaccine targets.
Triclabendazole 10 mg/kg as a single dose is the preventive chemotherapy for fascioliasis and is recommended in subdistricts, villages, or communities with clustering of cases. The WHO recommends that all school-aged children (aged 5-14 years) or all residents should be given the preventive chemotherapy every 12 months.
Praziquantel 40 mg/kg as a single dose is the preventive chemotherapy for clonorchiasis and opisthorchiasis and is recommended in all people residing in areas where the prevalence of infection is 20% and above. Among people who live in areas with less than 20% prevalence, the recommendation is to administer preventive chemotherapy (1) to everyone every 24 months or (2) every 12 months to those who eat raw fish.
Light infections may resolve spontaneously within one year, even without treatment. The prognosis may be grave in patients with heavy infection.
Immunocompromised hosts may be at an increased risk of complications. For example, G seoi worms were found to penetrate into colonic lymphoid tissue in a patient with colon cancer.
Instruct patients on proper food preparation to avoid infection with intestinal flukes. Thoroughly cooking fish and mollusks is always recommended.
Educational interventions that emphasize avoidance of fecal contamination of water where fish and aquatic plants thrive are recommended to prevent intestinal trematode infections.
Neglected Tropical Diseases. World Health Organization. Available at http://www.who.int/neglected_diseases/diseases/en/.
Toledo R, Munoz-Antoli C, Esteban JG. Intestinal Trematode Infections. Toledo R, Fried B. Digenetic Trematodes, Advances in Experimental Medicine and Biology. New York: Springer Science+Business Media; 2014. 766: 201-240.
Chai JY, Shin EH, Lee SH, Rim HJ. Foodborne intestinal flukes in Southeast Asia. Korean J Parasitol. 2009 Oct. 47 Suppl:S69-102. [Medline]. [Full Text].
Fürst T, Sayasone S, Odermatt P, Keiser J, Utzinger J. Manifestation, diagnosis, and management of foodborne trematodiasis. BMJ. 2012 Jun 26. 344:e4093. [Medline].
Toledo R, Esteban JG, Fried B. Current status of food-borne trematode infections. Eur J Clin Microbiol Infect Dis. 2012 Aug. 31 (8):1705-18. [Medline].
Biswal DK, Ghatani S, Shylla JA, Sahu R, Mullapudi N, Bhattacharya A, et al. An integrated pipeline for next generation sequencing and annotation of the complete mitochondrial genome of the giant intestinal fluke, Fasciolopsis buski (Lankester, 1857) Looss, 1899. PeerJ. 2013 Nov 12. 1:e207. [Medline]. [Full Text].
Kumar V. The digenetic trematodes, Fasciolopsis buski, Gastrodiscoides hominis and Artyfechinostomum malayanum, as zoonotic infections in South Asian countries. Ann Soc Belg Med Trop. 1980 Dec. 60(4):331-9. [Medline].
Seo M, Shin DH, Guk SM, Oh CS, Lee EJ, Shin MH, et al. Gymnophalloides seoi eggs from the stool of a 17th century female mummy found in Hadong, Republic of Korea. J Parasitol. 2008 Apr. 94(2):467-72. [Medline].
Bhattacharjee HK, Yadav D, Bagga D. Fasciolopsiasis presenting as intestinal perforation: a case report. Trop Gastroenterol. 2009 Jan-Mar. 30(1):40-1. [Medline].
Chai JY. Echinotomes in humans. Fried B, Toledo R, eds. The Biology of Echinostomes. New York, NY: Springer; 2009.
Toledo R, Esteban JG, Fried B. Immunology and pathology of intestinal trematodes in their definitive hosts. Adv Parasitol. 2006. 63:285-365. [Medline].
Cho YK, Ryang YS, Kim IS, Park SK, Im JA, Lee KJ. Differential immune profiles following experimental Echinostoma hortense infection in BALB/c and C3H/HeN mice. Parasitol Res. 2007 Apr. 100(5):1053-61. [Medline].
Sotillo J, Muñoz-Antoli C, Marcilla A, Fried B, Guillermo Esteban J, Toledo R. Echinostoma caproni: kinetics of IgM, IgA and IgG subclasses in the serum and intestine of experimentally infected rats and mice. Exp Parasitol. 2007 Aug. 116(4):390-8. [Medline].
Cortés A, Muñoz-Antoli C, Martín-Grau C, Esteban JG, Grencis RK, Toledo R. Differential alterations in the small intestine epithelial cell turnover during acute and chronic infection with Echinostoma caproni (Trematoda). Parasit Vectors. 2015 Jun 18. 8:334. [Medline].
Lee JJ, Kim HJ, Kim MJ, Yi Lee JW, Jung BK, Lee JY. Decrease of Metagonimus yokogawai endemicity along the Tamjin River basin. Korean J Parasitol. 2008 Dec. 46(4):289-91. [Medline]. [Full Text].
Yu JR, Chung JS, Huh S, Lee SH, Chai JY. PCR-RFLP pattern of three kinds of Metagonimus in Korea. Korean J Parasitol. 1997 Dec. 35(4):271-6. [Medline].
Belizario, VY Jr, Bersabe, MJ, de Leon, WU, et al. Intestinal heterophyidiasis: an emerging food-borne parasitic zoonosis in southern Philippines. Southeast Asian J Trop Med Public Health. 2001. 32; Suppl 2:36-42. [Medline].
Bunnag T, Sornmani S, Impand P. Potential health hazards of the water resources development: a health survey in the Phitsanulok Irrigation Project, Nan River Basin, Northern Thailand. Southeast Asian J Trop Med Public Health. 1980 Dec. 11(4):559-65. [Medline].
Chandra SS. Epidemiology of Fasciolopsis buski in Uttar Pradesh. Indian J Med Res. 1984 Jan. 79:55-9. [Medline].
Gilman RH, Mondal G, Maksud M. Endemic focus of Fasciolopsis buski infection in Bangladesh. Am J Trop Med Hyg. 1982 Jul. 31(4):796-802. [Medline].
Hadidjaja P, Dahri HM, Roesin R. First autochthonous case of Fasciolopsis buski infection in Indonesia. Am J Trop Med Hyg. 1982 Sep. 31(5):1065. [Medline].
Lo CT, Lee KM. Intestinal parasites among the Southeast Asian laborers in Taiwan during 1993-1994. Zhonghua Yi Xue Za Zhi (Taipei). 1996 Jun. 57(6):401-4. [Medline].
Xu L, Jiang Z, Yu S. [Characteristics and recent trends in endemicity of human parasitic diseases in China]. Chung Kuo Chi Sheng Chung Hsueh Yu Chi Sheng Chung Ping Tsa Chih. 1995. 13(3):214-7. [Medline].
Rowel C, Fred B, Betson M, Sousa-Figueiredo JC, Kabatereine NB, Stothard JR. Environmental epidemiology of intestinal schistosomiasis in Uganda: population dynamics of biomphalaria (gastropoda: planorbidae) in Lake Albert and Lake Victoria with observations on natural infections with digenetic trematodes. Biomed Res Int. 2015. 2015:717261. [Medline].
Ashrafi K, Saadat F, O'Neill S, Rahmati B, Amin Tahmasbi H, Pius Dalton J, et al. The Endemicity of Human Fascioliasis in Guilan Province, Northern Iran: the Baseline for Implementation of Control Strategies. Iran J Public Health. 2015 Apr. 44 (4):501-11. [Medline].
Achra A, Prakash P, Shankar R. Fasciolopsiasis: Endemic focus of a neglected parasitic disease in Bihar. Indian J Med Microbiol. 2015 Jul-Sep. 33 (3):364-8. [Medline].
Chai JY, Jung BK, Kim DG, Kim JL, Lim H, Shin EH, et al. Heterophyid trematodes recovered from people residing along the Boseong River, South Korea. Acta Trop. 2015 Aug. 148:142-6. [Medline].
Liu ZX, Zhang Y, Liu YT, Chang QC, Su X, Fu X, et al. Complete Mitochondrial Genome of Echinostoma hortense (Digenea: Echinostomatidae). Korean J Parasitol. 2016 Apr. 54 (2):173-9. [Medline].
Chai JY, Sohn WM, Jung BK, Yong TS, Eom KS, Min DY, et al. Intestinal Helminths Recovered from Humans in Xieng Khouang Province, Lao PDR with a Particular Note on Haplorchis pumilio Infection. Korean J Parasitol. 2015 Aug. 53 (4):439-45. [Medline].
Jejaw A, Zemene E, Alemu Y, Mengistie Z. High prevalence of Schistosoma mansoni and other intestinal parasites among elementary school children in Southwest Ethiopia: a cross-sectional study. BMC Public Health. 2015 Jul 2. 15:600. [Medline].
Doanh PN, Nawa Y. Clonorchis sinensis and Opisthorchis spp. in Vietnam: current status and prospects. Trans R Soc Trop Med Hyg. 2016 Jan. 110 (1):13-20. [Medline].
Tribble D, Wagner KF. Trematode infections. Infectious Disease Practice. 1996. 20:69-73.
Quang TD, Duong TH, Richard-Lenoble D, Odermatt P, Khammanivong K. [Emergence in humans of fascioliasis (from Fasciola gigantica) and intestinal distomatosis (from Fasciolopsis buski) in Laos]. Sante. 2008 Jul-Sep. 18(3):119-24. [Medline].
Kajugu PE, Hanna RE, Edgar HW, McMahon C, Cooper M, Gordon A, et al. Fasciola hepatica: Specificity of a coproantigen ELISA test for diagnosis of fasciolosis in faecal samples from cattle and sheep concurrently infected with gastrointestinal nematodes, coccidians and/or rumen flukes (paramphistomes), under field conditions. Vet Parasitol. 2015 Sep 15. 212 (3-4):181-7. [Medline].
Worasith C, Kamamia C, Yakovleva A, Duenngai K, Wangboon C, Sithithaworn J, et al. Advances in the Diagnosis of Human Opisthorchiasis: Development of Opisthorchis viverrini Antigen Detection in Urine. PLoS Negl Trop Dis. 2015 Oct. 9 (10):e0004157. [Medline].
Teimoori S, Arimatsu Y, Laha T, Kaewkes S, Sereerak P, Sripa M, et al. Chicken IgY-based coproantigen capture ELISA for diagnosis of human opisthorchiasis. Parasitol Int. 2016 Apr 29. [Medline].
Sapero JJ, Lawless DK. The MIF stain-preservation technic for the identification of intestinal protozoa. Am J Trop Med Hyg. 1953 Jul. 2(4):613-9. [Medline]. [Full Text].
Price DL. Comparison of three collection-preservation methods for detection of intestinal parasites. J Clin Microbiol. 1981 Dec. 14(6):656-60. [Medline]. [Full Text].
Wang LC. Improvement in the identification of intestinal parasites by a concentrated merthiolate-iodine-formaldehyde technique. J Parasitol. April 1998. 84(2):457-8. [Medline].
Jeon HK, Lee D, Park H, Min DY, Rim HJ, Zhang H, et al. Human infections with liver and minute intestinal flukes in Guangxi, China: analysis by DNA sequencing, ultrasonography, and immunoaffinity chromatography. Korean J Parasitol. 2012 Dec. 50(4):391-4. [Medline]. [Full Text].
Yang HJ, Guk SM, Han ET, Chai JY. Molecular differentiation of three species of Metagonimus by simple sequence repeat anchored polymerase chain reaction (SSR-PCR) amplification. J Parasitol. 2000 Oct. 86(5):1170-2. [Medline].
Yu JR, Chai JY. Metagonimus. Liu D, ed. Molecular Detection of Foodborne Pathogens. Boca Raton, Florida: CRC Press (Taylor & Francis Group); 2010. Ch 59.
Dzikowski R, Levy MG, Poore MF, Flowers JR, Paperna I. Use of rDNA polymorphism for identification of Heterophyidae infecting freshwater fishes. Dis Aquat Organ. 2004 Apr 21. 59(1):35-41. [Medline].
Kumchoo K, Wongsawad C, Vanittanakom P, Chai JY, Rojanapaibul A. Effect of niclosamide on the tegumental surface of Haplorchis taichui using scanning electron microscopy. J Helminthol. 2007 Dec. 81(4):329-37. [Medline].
Kolenyak-Santos F, Garnero C, de Oliveira RN, de Souza AL, Chorilli M, Allegretti SM, et al. Nanostructured Lipid Carriers as a Strategy to Improve the In Vitro Schistosomiasis Activity of Praziquantel. J Nanosci Nanotechnol. 2015 Jan. 15 (1):761-72. [Medline].
Soukhathammavong P, Odermatt P, Sayasone S, et al. Efficacy and safety of mefloquine, artesunate, mefloquine-artesunate, tribendimidine, and praziquantel in patients with Opisthorchis viverrini: a randomised, exploratory, open-label, phase 2 trial. Lancet Infect Dis. 2011 Feb. 11(2):110-8. [Medline].
Foodborne trematodiasis. World Health Organization. Available at http://www.who.int/mediacentre/factsheets/fs368/en/. March 2016;
Worasith C, Kamamia C, Yakovleva A, Duenngai K, Wangboon C, Sithithaworn J, et al. Advances in the Diagnosis of Human Opisthorchiasis: Development of Opisthorchis viverrini Antigen Detection in Urine. PLoS Negl Trop Dis. 2015. 9 (10):e0004157. [Medline].
McNeilly TN, Nisbet AJ. Immune modulation by helminth parasites of ruminants: implications for vaccine development and host immune competence. Parasite. 2014. 21:51. [Medline].
Seo M, Chun H, Ahn G, Jang KT, Guk SM, Chai JY. A case of colonic lymphoid tissue invasion by Gymnophalloides seoi in a Korean man. Korean J Parasitol. 2006 Mar. 44(1):87-9. [Medline]. [Full Text].
Adams M, Motarjemi Y. Basic Food Safety for Health Workers. 1999.
Ahn YK. [Intestinal flukes of genus Metagonimus and their second intermediate hosts in Kangwon-do]. Korean J Parasitol. 1993 Dec. 31(4):331-40. [Medline].
Berger SA, Marr JS. Human Parasitic Diseases Sourcebook. First ed. Sudbury, MA: Jones and Bartlett; 2006.
Bunnag D, Radomyos P, Harinasuta T. Field trial on the treatment of fasciolopsiasis with praziquantel. Southeast Asian J Trop Med Public Health. 1983 Jun. 14(2):216-9. [Medline].
Chai JY, Kim IM, Seo M. A new endemic focus of Heterophyes nocens, Pygidiopsis summa, and other intestinal flukes in a coastal area of Muan-gun, Chollanam-do. Korean J Parasitol. 1997 Dec. 35(4):233-8. [Medline].
Chai JY, Lee SH. Food-borne intestinal trematode infections in the Republic of Korea. Parasitol Int. 2002 Jun. 51(2):129-54. [Medline].
Chung DI, Moon CH, Kong HH, Choi DW, Lim DK. The first human case of Clinostomum complanatum (Trematoda: Clinostomidae) infection in Korea. Korean J Parasitol. 1995 Sep. 33(3):219-23. [Medline].
Drugs For Parasitic Infections. The Medical Letter. August 2004. 46(1189):e1-e12.
Drugs for Parasitic Infections. Medical Let Drugs Ther. 2004. [Full Text].
Eastburn RL, Fritsche TR, Terhune CA Jr. Human intestinal infection with Nanophyetus salmincola from salmonid fishes. Am J Trop Med Hyg. 1987 May. 36(3):586-91. [Medline].
Eckert J. Workshop summary: food safety: meat- and fish-borne zoonoses. Vet Parasitol. 1996 Aug. 64(1-2):143-7. [Medline].
Fernandes BJ, Cooper JD, Cullen JB, Freeman RS, Ritchie AC, Scott AA. Systemic infection with Alaria americana (Trematoda). Can Med Assoc J. 1976 Dec 4. 115(11):1111-4. [Medline].
Gai L, Ma X, Fu Y, Huang D. [Relationship between the rate of parasitic infection and the knowledge of prevention]. Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi. 1995. 13(4):269-72. [Medline].
Gajadhar AA, Scandrett WB, Forbes LB. Overview of food- and water-borne zoonotic parasites at the farm level. Rev Sci Tech. 2006 Aug. 25(2):595-606. [Medline].
Graczyk TK, Fried B. Echinostomiasis: a common but forgotten food-borne disease. Am J Trop Med Hyg. 1998 Apr. 58(4):501-4. [Medline].
Graczyk TK, Gilman RH, Fried B. Fasciolopsiasis: is it a controllable food-borne disease?. Parasitol Res. 2001 Jan. 87(1):80-3. [Medline].
Guk SM, Park JH, Shin EH, Kim JL, Lin A, Chai JY. Prevalence of Gymnophalloides seoi infection in coastal villages of Haenam-gun and Yeongam-gun, Republic of Korea. Korean J Parasitol. 2006 Mar. 44(1):1-5. [Medline]. [Full Text].
Harinasuta T, Bunnag D, Radomyos P. Efficacy of praziquantel on fasciolopsiasis. Arzneimittelforschung. 1984. 34(9B):1214-5. [Medline].
Kaul BK, Singhal GD, Pillai PN. Artyfechinostomum mehrai infestation with bowel perforation. J Indian Med Assoc. 1974 Oct 16. 63(8):263-5. [Medline].
Keiser J, Utzinger J. Food-borne trematodiases. Clin Microbiol Rev. 2009 Jul. 22(3):466-83. [Medline]. [Full Text].
Kim DG, Kim TS, Cho SH, Song HJ, Sohn WM. Heterophyid metacercarial infections in brackish water fishes from Jinju-man (Bay), Kyongsangnam-do, Korea. Korean J Parasitol. 2006 Mar. 44(1):7-13. [Medline]. [Full Text].
Leung TL, Poulin R, Keeney DB. Accumulation of diverse parasite genotypes within the bivalve second intermediate host of the digenean Gymnophallus sp. Int J Parasitol. 2009 Feb. 39(3):327-31. [Medline].
Liu LX, Harinasuta KT. Liver and intestinal flukes. Gastroenterol Clin North Am. 1996 Sep. 25(3):627-36. [Medline].
Maclean JD, Cross J, Mahanty S. Liver, lung, and intestinal fluke infections. Guerrant RL, Walker DH, Weller PF, eds. Tropical Infectious Diseases: Principles, Pathogens and Practice. 2nd ed. Philadelphia, PA: Churchill Livingstone; 2006. 1349 ff.
Malviya HC. The susceptibility of mammals to Fasciolopsis buski. J Helminthol. 1985 Mar. 59(1):19-22. [Medline].
Manjarumkar PV, Shah PM. Epidemiological study of Fasciolopsis Buski in Palghar Taluk. Indian J Public Health. 1972 Jan. 16(1):3-6. [Medline].
Manning GS, Ratanarat C. Fasciolopsis buski (Lankester, 1857) in Thailand. Am J Trop Med Hyg. 1970 Jul. 19(4):613-9. [Medline].
Mas-Coma S, Valero MA, Bargues MD. Chapter 2. Fasciola, lymnaeids and human fascioliasis, with a global overview on disease transmission, epidemiology, evolutionary genetics, molecular epidemiology and control. Adv Parasitol. 2009. 69:41-146. [Medline].
McDonald HR, Kazacos KR, Schatz H, Johnson RN. Two cases of intraocular infection with Alaria mesocercaria (Trematoda). Am J Ophthalmol. 1994 Apr 15. 117(4):447-55. [Medline].
Muttalib MA, Islam N. Fasciolopsis buski in Bangladesh-a pilot study. J Trop Med Hyg. 1975 Jun. 78(6):135-7. [Medline].
Park JH, Kim JL, Shin EH, Guk SM, Park YK, Chai JY. A new endemic focus of Heterophyes nocens and other heterophyid infections in a coastal area of Gangjin-gun, Jeollanam-do. Korean J Parasitol. 2007 Mar. 45(1):33-8. [Medline]. [Full Text].
Plaut AG, Kampanart-Sanyakorn C, Manning GS. A clinical study of Fasciolopsis buski infection in Thailand. Trans R Soc Trop Med Hyg. 1969. 63(4):470-8. [Medline].
Pungpak S, Radomyos P, Radomyos BE. Treatment of Opisthorchis viverrini and intestinal fluke infections with Praziquantel. Southeast Asian J Trop Med Public Health. 1998 Jun. 29(2):246-9. [Medline].
Radomyos B, Wongsaroj T, Wilairatana P. Opisthorchiasis and intestinal fluke infections in northern Thailand. Southeast Asian J Trop Med Public Health. 1998 Mar. 29(1):123-7. [Medline].
Radomyos P, Radomyos B, Tungtrongchitr A. Multi-infection with helminths in adults from northeast Thailand as determined by post-treatment fecal examination of adult worms. Trop Med Parasitol. 1994 Jun. 45(2):133-5. [Medline].
Shah PM, Udani PM, Manjarumkar PV. Fasciolopsis Buski infestation in children. Indian Pediatr. 1973 Dec. 10(12):721-4. [Medline].
Suntharasamai P, Bunnag D, Tejavanij S. Comparative clinical trials of niclosamide and tetrachlorethylene in the treatment of Fasciolopsis buski infection. Southeast Asian J Trop Med Public Health. 1974 Dec. 5(4):556-9. [Medline].
Taraschewski H, Mehlhorn H, Bunnag D. Effects of praziquantel on human intestinal flukes (Fasciolopsis buski and Heterophyes heterophyes). Zentralbl Bakteriol Mikrobiol Hyg [A]. 1986 Nov. 262(4):542-50. [Medline].
Waikagul J. Intestinal fluke infections in Southeast Asia. Southeast Asian J Trop Med Public Health. 1991 Dec. 22 Suppl:158-62. [Medline].
Wegner DH. The profile of the trematodicidal compound praziquantel. Arzneimittelforschung. 1984. 34(9B):1132-6. [Medline].
Wiwanitkit V, Nithiuthai S, Suwansaksri J. Motility of minute intestinal fluke, Haplorchinae spp, metacercariae in fish dishes prepared by different uncooked methods. MedGenMed. 2002 Mar 6. 4(1):8. [Medline].
Wiwanitkit V, Suwansaksri J, Chaiyakhun Y. High prevalence of Fasciolopsis buski in an endemic area of liver fluke infection in Thailand. MedGenMed. 2002 Jul 9. 4(3):6. [Medline].
|Fasciolopsiasis||Freshwater plants (water caltrop, water chestnut)||China, Thailand, Bangladesh, India|
|Echinostomiasis||Tadpoles, freshwater snails, fish, frogs||Indonesia, Philippines, Taiwan, Thailand|
|Heterophyiasis||Fish||Egypt, Iran, Tunisia, Turkey|
|Metagonimiasis||Fish (cyprinid)||Far East, Spain, Eastern Europe|
|*Adapted with permission from Tribble D, Wagner KF. Trematode infections. Infectious Disease Practice. 1996;20:69-73.|
|Alaria americana||Undercooked frog legs||Disseminated fatal thoracic, gastrointestinal, retroperitoneal, and CNS manifestations; intraocular infections|
|Echinostomiasis (16 species)||Freshwater fish, aquatic plants, clams, snails, mollusks, contact with aquatic birds||May be asymptomatic; mild abdominal pain, bloating, dyspepsia, diarrhea, eosinophilia|
|Fibricola species||Tadpoles||Abdominal pain, diarrhea, fever, eosinophilia|
|Fasciolopsis species||Water chestnut, water calthrop, water bamboo, water morning glory lotus and water hyacinth||May be symptomatic; may be subclinical; gastritis, nausea, diarrhea, eosinophilia; generalized edema in persons with heavy infection burden|
|Gastrodiscoides species||Vegetables, aquatic plants||Often asymptomatic; may manifest as abdominal pain and diarrhea in severe cases|
|Watsonius watsoni||Water bamboo||Severe diarrhea|
|Fischoederius elongates||Aquatic plants||Epigastric pain and vomiting|
|Heterophyes species||Mullets, fish; brackish water||May be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss|
|Gymnophalloides seoi||Oysters||Fever, abdominal pain, anorexia, weight loss, diarrhea, pancreatitis|
|Carneophallus brevicaeca||Shrimp||Fatal when infection involves CNS and heart|
|Brachylaima ruminae||Poultry, rats||Abdominal pain, diarrhea|
|Metagonimiasis species||Fish (ayu, golden carp)||May be asymptomatic; intestinal mucosal disease, ulcer-related abdominal pain, dyspepsia, nausea, vomiting, diarrhea, weight loss|
|Nanophyetus salmincola||Undercooked 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.|