Fasciola hepatica

From Cow
Fasciola hepatica egg under light microscopy

Fasciola hepatica is a parasitic trematode (fluke) of cattle worldwide.

Fasciola magna and Fasciola gigantica are also prevalent in cattle and coinfections can occur[1].

Although this parasite normally causes only chronic liver disease in cattle, it is an important zoonotic parasite[2].

The life cycle involves intermediate snail hosts (Lymnaea spp) with infective metacercariae that are eaten by cattle during grazing. The adult fluke usually resides in the bile duct of cattle and cause extensive liver disease during their migration. 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 fasciola eggs and elevated bilirubin and liver enzyme on blood tests may help determine a diagnosis. In acute fasciolosis, acute hepatitis is a common sequelae, which usually leads to cirrhosis in more chronic cases[3]. Bile duct walls may become greatly thickened and calcified and adult flukes may also be found in aberrant sites such as the lungs. Mixed infections with F. magna can be seen in cattle.

Diagnosis is based on presenting clinical signs, isolation of the parasite eggs in feces, identification of adult flukes in the liver and laboratory analysis of parasite for identification. Commercially available ELISA are also available in some countries. It should be also noted that intradermal tuberculin test used to diagnose tuberculosis is reduced in cattle co-infected with F. hepatica[4].

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. Shu FF et al (2012) Characterization of Fasciola Samples by ITS of rDNA Sequences Revealed the Existence of Fasciola hepatica and Fasciola gigantica in Yunnan Province, China. J Parasitol 98(4):889-890
  2. Arslan F et al (2012) Fascioliasis: 3 cases with three different clinical presentations. Turk J Gastroenterol 23(3):267-271
  3. Haçarız O et al(2012) A Proteomic Approach To Investigate the Distribution and Abundance of Surface and Internal Fasciola hepatica Proteins during the Chronic Stage of Natural Liver Fluke Infection in Cattle. J Proteome Res 11(7):3592-3604
  4. Claridge J et al (2012) Fasciola hepatica is associated with the failure to detect bovine tuberculosis in dairy cattle. Nat Commun 3:853
  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