Clonorchis spp

From Dog
Adult C. sinensis[1]

Clonorchis spp are a parasitic zoonotic trematode of dogs and cats in South-east Asia[2].

Species which are pathogenic to dogs include:

  • Clonorchis sinensis

These trematodes rely on two intermediate hosts (snails and marine fish[3]). Dogs become infected primarily through consumption of raw or undercooked fish. The local waters can be contaminated with C. sinensis eggs by using untreated feces as fertilizer for farming and by scrubbing pail latrines in the ponds[4]. These flukes can survive within the dog for up to 10 years[5].

Metacercaria are ingested by dogs, which migrate up the bile and pancreatic ducts, where they lay eggs[6].

Clinical signs in dogs are usually absent but migration of immature flukes can cause acute hepatitis and pancreatitis[7].

Infections with C. sinensis are associated with periductal and portal tract inflammation, with congestion of hepatic sinusoids during the acute phase and in chronic cases, development of bile duct carcinoma.

Hematological changes include increased activity of glutamate dehydrogenase[8].

Diagnosis is based on identification of eggs in feces using ethyl acetate sedimentation[9].

A differential diagnosis would include other hepatic and bile duct flukes such as Parametorchis complexus, Opisthorchis felineus and Metorchis spp.

Treatment is effective with praziquantel[10] at 25 mg/kg three times daily for 3 days. Sustained-release tablets are also available for dogs[11].

CT studies have revealed that treatment is associated with periductal hyalinization, degeneration of the periductal arteries, and calcification of the ductal epithelium[12].

Preventative measures require addressing infection of dogs from contaminated water sources and eating undercooked fish[13].


  1. Kansas State Uni
  2. Lin RQ et al (2011) Prevalence of Clonorchis sinensis infection in dogs and cats in subtropical southern China. Parasit Vectors 4:180
  3. Cribb TH et al (1999) Faustulid trematodes (Digenea) from marine fishes of Australia. Syst Parasitol 44(2):119-138
  4. Duan JH et al (2009) Epidemiological survey on clonorchiasis sinensis in an endemic area of South Hunan Province. Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi 27(6):467-471
  5. Harinasuta C & Harinasuta T (1984) Opisthorchis viverrini: life cycle, intermediate hosts, transmission to man and geographical distribution in Thailand. Arzneimittelforschung 34(9B):1164-1167
  6. Bowman, DD (2009) Georgis' parasitology for veterinarians. Elsevier Saunders, Missouri. pp:125-126
  7. Mills JH & Hirth RS (1968) Lesions caused by the hepatic trematode, Metorchis conjunctus, Cobbold, 1860. A comparative study in carnivora. J Small Anim Pract 9(1):1-6
  8. Schuster RK et al (2007) Liver flukes in dogs and treatment with praziquantel. Vet Parasitol 150(4):362-365
  9. Okaeme AN (1985) Zoonotic helminths of dogs and cats at New Bussa, Kainji Lake area, Nigeria. Int J Zoonoses 12(3):238-240
  10. Schuster RK et al (2007) Liver flukes in dogs and treatment with praziquantel. Vet Parasitol 150(4):362-365
  11. Hong ST et al (2003) Sustained-release praziquantel tablet: pharmacokinetics and the treatment of clonorchiasis in beagle dogs. Parasitol Res 91(4):316-320
  12. Lee KH et al (2003) Experimental clonorchiasis in dogs: CT findings before and after treatment. Radiology 228(1):131-138
  13. Lin R et al (2005) Investigation on the epidemiological factors of Clonorchis sinensis infection in an area of south China. Southeast Asian J Trop Med Public Health 36(5):1114-1117