Experimentally induced Fasciola hepatica infection in young calves.

Twenty-four calves between 1 and 66 days of age (allotted to 3 age groups) were each inoculated with 100 Fasciola hepatica metacercariae to determine their susceptibility to fluke infection. Studies included measuring the immune response, as determined by enzyme-linked immunosorbent assay, fecal egg counts (to evaluate the length of the life cycle between times of metacercariae ingestion and fluke maturation), and the numbers of flukes in the liver of the calves at slaughter. Fasciola hepatica ova started appearing in the feces of calves, all ages, at 60 days after inoculations were done and reached average maximal number by 80 to 90 days. The enzyme-linked immunosorbent assay results indicated that the oldest group of calves had significantly (P less than 0.01) greater antibody concentration from 6 weeks until the 18th to 20th week after inoculation than did the 2 younger groups. At slaughter, calves in the 52- to 66-day age group had mean fluke numbers significantly (P less than 0.01) greater than did calves in the 1- to 27-day and 35- to 44-day age groups.