Clonorchis spp

From Cow
Adult Clonorchis flatworm

Clonorchis spp are a parasitic digenetic trematode which infects cattle in Asian countries.

Clonorchis spp are important zoonotic flatworms which are endemic in Asia and cause hepatic cancer in humans[1]. Cattle are considered incidental hosts and rarely cause disease in this host.

Species which are pathogenic in cattle include:

  • Clonorchis sinensis[2]

The life cycle involves intermediate snail hosts (Lymnaea spp) with infective metacercariae that are normally eaten by pigs, but can be consumed by cattle during grazing. The adult fluke usually reside in the peripheral small bile ducts of the liver and produce chronic inflammation of the bile duct, bile duct dilatation, mechanical obstruction, and bile duct wall thickening[3]. Once mature, the flukes pass eggs into the bile, which are passed out in the feces and contaminate pasture. Other animals, as well as humans become infected by eating uncooked beef.

Clinical signs are often vague in cattle and laboratory testing for Clonorchis eggs and elevated bilirubin and liver enzyme on blood tests may help determine a diagnosis. In acute infections, acute hepatitis is a common sequelae, which usually leads to cirrhosis in more chronic cases. Bile duct walls may become greatly thickened and calcified and adult flukes may also be found in aberrant sites such as the lungs.

Diagnosis is based on presenting clinical signs, isolation of the parasite eggs in feces, identification of adult flukes in the liver[4] and laboratory analysis of parasite for identification. Commercially available ELISA are also available in some countries.

Control of this parasite is through use of molluscicides to control the snail (intermediate host) as well as flukicidal drugs such as triclabendazole, closantel, moxidectin plus triclabendazole and oxyclozanide[5].

Herd milk sample monitoring is an effective way of assessing control of this parasite[6].

References

  1. Suttiprapa S et al (2009) Ov-APR-1, an aspartic protease from the carcinogenic liver fluke, Opisthorchis viverrini: functional expression, immunolocalization and subsite specificity. Int J Biochem Cell Biol 41(5):1148-1156
  2. Sun T & Gibson JB (1979) The sites of antigen formation in different developmental stages of Clonorchis sinensis. Jpn J Med Sci Biol 22(4):263-271
  3. Lim JH et al (2008) Biliary parasitic diseases including clonorchiasis, opisthorchiasis and fascioliasis. Abdom Imaging 33(2):157-165
  4. Singh M et al (1991) Current status of food-borne parasitic zoonoses in Singapore. Southeast Asian J Trop Med Public Health 22:27-30
  5. Merck Vet Manual
  6. Kuerpick B et al (2012) Bulk milk-estimated seroprevalence of Fasciola hepatica in dairy herds and collecting of risk factor data in East Frisia, northern Germany. Berl Munch Tierarztl Wochenschr 125(7-8):345-350