Early immunodiagnosis of bovine fascioliasis using the specific antigen f2 in a passive hemagglutination test.

An improved hemagglutination (HA) test using the purified specific f2 antigen of Fasciola hepatica has been evaluated with regard to its potential use for early diagnosis of infection. On experimental infection of beef calves 6-8 months of age, f2-specific antibodies were detected 2-4 weeks after inoculation and persisted at high levels during the 28 week experimental period. On natural infection of dairy calves, 6-9 months of age, allowed to graze in infected fields from April to June, 48% of the animals were positive in July although coproscopic analyses were negative. In November all the calves were HA positive but only 24% of them excreted F. hepatica eggs. Beef calves 1-3 months of age allowed to graze with their dams in infected fields continued to suckle their dams and were weakly infected according to HA results. This weak infection was not detected by coproscopical analysis. Colostral f2-specific antibodies persisted for approximately 6 months in the serum of dairy calves allowed to suckle their dams immediately after birth.