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Opisthorchis spp. - Pathogen Safety Data Sheet


NAME: Opisthorchis spp.

SYNONYM OR CROSS REFERENCE: Opisthorchiasis, clonorchiasis, Opisthorchis felineus, Opisthorchis viverrini, cat liver-fluke disease, pa-yard bai-mai nai tub Footnote 1Footnote 2

CHARACTERISTICS: Opisthorchis spp. is a genus of trematode liver flukes belonging to the Opisthorchiidae family Footnote 3. Adults measure 5-10 mm in length, 0.8-1.9 mm in width, and reside in the gall bladder, biliary ducts and (less frequently) pancreatic ducts of its definitive mammalian host Footnote 2Footnote 4Footnote 5. Eggs are ingested by the first intermediate host (snails). Several species of the prosobranch gastropod genus Bithynia serve as the first intermediate host. Within the snails, eggs release miracidia, which develop through sporocyst, rediae, and cercariae stages over a period of 6 to 8 weeks Footnote 3Footnote 6. Cercariae are released and penetrate freshwater fish (the second intermediate host), encysting in their muscles as metacercariae. The definitive hosts are infected by ingesting undercooked or raw fish harbouring metacercariae. Once mature, the adults release eggs which the host sheds in its feces. The eggs produced are yellow-brown, oval, and approximately 27 µm by 16 µm Footnote 5Footnote 7.


PATHOGENICITY/TOXICITY: There is consensus that the biology and pathologic characteristics of Opisthorchis and Clonorchis are the same, essentially low grade biliary tract pathogens.  The majority of Opisthorchis infections (around 80%) are light infections Footnote 1Footnote 2. Classified by less than 1000 eggs/g of feces, a light infection is usually asymptomatic except for eosinophilia Footnote 2. With this stage, there is no noticeable damage to liver function Footnote 2. A heavy infection is classified by 10,000-30,000 eggs/g of feces Footnote 2. The clinical presentation of a heavy infection includes diarrhea, constipation, abdominal pain, anorexia, indigestion, gastrointestinal bleeding, lassitude, mild fever, jaundice, enlarged or non-functional gall bladder, cholecystitis, cholangitis, liver abscess, and gallstones Footnote 2Footnote 3Footnote 7. Clinical presentation of untreated chronic infection includes oedema of the legs, ascites, mild cirrhosis, hepatomegaly, and biliary epithelium hyperplasia and inflammation Footnote 2. Cholangiocarcinoma is strongly associated with O. viverrini infection and has a high mortality rate Footnote 2. It usually develops 30-40 years after initial infection, and its victims usually die within 3-6 months Footnote 2Footnote 8.

EPIDEMIOLOGY: O. viverrini is endemic in Thailand, Laos, and Cambodia. O. felineus is reported in North Europe and Asia Footnote 2. Infection is more common from September to February. In endemic areas, infection rates can be up to 90% in humans, and 97% in fish Footnote 5. Infection is uncommon in children under 5 years of age. Prevalence of Opisthorchiasis is higher in areas that are poor or unsanitary Footnote 9Footnote 10.

HOST RANGE: Humans, snails, fish, cats, dogs, reptiles, amphibians, and fish-eating animals Footnote 4Footnote 11-13

INFECTIOUS DOSE: Possibly as low as 1-2 metacercariae Footnote 8.

MODE OF TRANSMISSION: Opisthorchis spp. are transmitted when raw or undercooked fish containing metacercariae is ingested Footnote 3.

INCUBATION PERIOD: Metacercariae reach the bile ducts a few hours after ingestion Footnote 7. Opisthorchis spp. take approximately 4 weeks to mature into adult worms and produce eggs.

COMMUNICABILITY: Not directly transmitted from person to person.


RESERVOIR: Cyprinoid fish, dogs, cats, pigs, rats, rabbits, fish-eating mammals Footnote 2Footnote 12Footnote 13.

ZOONOSIS: Yes, infection can be acquired from definitive hosts including domestic cats and dogs Footnote 2Footnote 12.

VECTORS: Snails Footnote 3.


DRUG SUSCEPTIBILITY: Sensitive to single dose praziquantel, and multi-dose albendazole Footnote 2Footnote 14Footnote 15.

SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 0.7% ammonium sulphate Footnote 7.

PHYSICAL INACTIVATION: Cysts are susceptible to deep freezing at -30oC for 32 hours Footnote 2. All stages of Opisthorchis spp. are susceptible to heating at 56oC for 30 minutes Footnote 16.

SURVIVAL OUTSIDE HOST: Cercariae remain infective in fresh water for about 20 hours Footnote 17.


SURVEILLANCE: Diagnosis of opisthorchiasis is as for clornorchiasis. Monitor for symptoms, confirm infection by microscopic demonstration of eggs in feces or duodenal juice (narrower than Clonorchis eggs) Footnote 2Footnote 14. ELISA can also be used to detect an O. viverrini antigen Footnote 2. Infection can be confirmed using PCR Footnote 5Footnote 18.

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: Praziquantel should be administered Footnote 2Footnote 14. If it is not tolerated, albendazole can be used as an alternative Footnote 14.





SOURCE/SPECIMENS: Feces, liver and spleen aspirates Footnote 3Footnote 5

PRIMARY HAZARDS: Ingestion of infective agents.

SPECIAL HAZARDS: Animals infected with Opisthorchis spp. are a potential hazard.



CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.

PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 19.

OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 19.


SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.

DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration.

STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled.


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: November 2011

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright © Public Health Agency of Canada, 2011 Canada


Footnote 1
Jong, E. C., Wasserheit, J. N., Johnson, R. J., Carberry, W. L., Agosti, J., Dunning, S., & Clark, H. (1985). Praziquantel for the treatment of Clonorchis/Opisthorchis infections: report of a double-blind, placebo-controlled trial. The Journal of Infectious Diseases, 152Footnote 3, 637-640.
Footnote 2
Muller, R., & Wakelin, D. (2002). Worms and human disease CABI publishing.
Footnote 3
Kaewpitoon, N., Kaewpitoon, S. J., Pengsaa, P., & Sripa, B. (2008). Opisthorchis viverrini: the carcinogenic human liver fluke. World Journal of Gastroenterology : WJG, 14(5), 666-674.
Footnote 4
Kaewkes, S. (2003). Taxonomy and biology of liver flukes. Acta Tropica, 88Footnote 3, 177-186.
Footnote 5
Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., Pfaller, M. A., & Yolken, R. H. (Eds.). (2003). Manual of Clinical Microbiology (8th ed.). Herdon, VA, United States of America: American Society for Microbiology.
Footnote 6
Harinasuta, C., & Harinasuta, T. (1984). Opisthorchis viverrini: life cycle, intermediate hosts, transmission to man and geographical distribution in Thailand. Arzneimittel-Forschung, 34(9B), 1164-1167.
Footnote 7
Cycle, L. (2008). Clonorchiasis and Opisthorchiasis. Wallace/Maxcy-Rosenau-Last Public Health & Preventive Medicine, , 445.
Footnote 8
Andrews, R. H., Sithithaworn, P., & Petney, T. N. (2008). Opisthorchis viverrini: an underestimated parasite in world health. Trends in Parasitology, 24(11), 497-501. doi:10.1016/
Footnote 9
Sripa, B. (2008). Concerted action is needed to tackle liver fluke infections in Asia. PLoS Neglected Tropical Diseases, 2(5), e232. doi:10.1371/journal.pntd.0000232
Footnote 10
Nithikathkul, C., Pumidonming, W., Wannapinyosheep, S., Tesana, S., Chaiprapathong, S., & Wongsawad, C. (2010). Opisthorchis viverrini infection in minute intestinal fluke endemic areas of Chiang Mai Province, Thailand. Asian Biomedicine (Research Reviews and News), 3(2), 187.
Footnote 11
Dorny, P., Praet, N., Deckers, N., & Gabriel, S. (2009). Emerging food-borne parasites. Veterinary Parasitology, 163(3), 196-206.
Footnote 12
Traub, R. J., Robertson, I. D., Irwin, P., Mencke, N., & Thompson, R. C. (2002). The role of dogs in transmission of gastrointestinal parasites in a remote tea-growing community in northeastern India. The American Journal of Tropical Medicine and Hygiene, 67(5), 539.
Footnote 13
Wykoff, D. E., Harinasuta, C., Juttijudata, P., & Winn, M. M. (1965). Opisthorchis viverrini in Thailand: The Life Cycle and Comparison with O. felineus. The Journal of Parasitology, 51(2), 207-214.
Footnote 14
Dancygier, H. (2010). Helminthic Infections. Clinical Hepatology, , 229-238.
Footnote 15
Kappagoda, S., Singh, U., & Blackburn, B. G. (2011). Antiparasitic therapy. Mayo Clinic Proceedings.Mayo Clinic, 86(6), 561-583. doi:10.4065/mcp.2011.0203
Footnote 16
Sirisinha, S., Rattanasiriwilai, W., Puengtomwatanakul, S., & Sobhon, P. (1986). Complement-mediated killing of Opisthorchis viverrini via activation of the alternative pathway. International Journal for Parasitology, 16(4), 341-346.
Footnote 17
Ilyinskikh, E. N., Lepyehin, A. V., Logvinov, S. V., & Ilyinskikh, N. N. (1998). Estimation of the mutagenic potential of the trematode Opisthorchis felineus in experimentally infected guinea pigs. Parasitology Research, 84(7), 570-572.
Footnote 18
Keiser, J., & Utzinger, J. (2009). Food-borne trematodiases. Clinical Microbiology Reviews, 22(3), 466-483. doi:10.1128/CMR.00012-09
Footnote 19
Public Health Agency of Canada. (2004). In Best M., Graham M. L., Leitner R., Ouellette M. and Ugwu K. (Eds.), Laboratory Biosafety Guidelines (3rd ed.). Canada: Public Health Agency of Canada.