Seroprevalence of Fasciola hepatica infection in sheep in northwestern Spain.

To estimate the prevalence of Fasciola hepatica infection in sheep in the León province (northwestern Spain), we conducted a survey between October 1992 and May 1993. A total of 767 samples of feces and serum were collected from sheep over 1 year of age belonging to 152 flocks randomly selected from the 4 natural regions of León province. Samples were analyzed by a standard coprological sedimentation method and an indirect enzyme-linked immunosorbent assay (ELISA) using excretory-secretory products from F. hepatica as the antigen. The results showed the feasibility of using the indirect ELISA to facilitate the serodiagnosis of ovine fasciolosis in seroepidemiology studies (95% sensitivity and > 99% specificity). No serological cross-reaction with infection by the trematode Dicrocoelium dendriticum was found. Furthermore, a statistically significant association was demonstrated between the mean flock prevalence results as determined by ELISA (77.6%) and by coprological examination (23.7%; P < 0.001). Differences in the results obtained by the two diagnostic methods could have been due to fluctuations in the numbers of fluke eggs detected in feces and to the persistence of specific antibodies in serum after an efficacious fasciolicide treatment. The median number of F. hepatica eggs detected per gram of feces was 10 (range, 5-450 eggs/g feces). The geographical distribution of F. hepatica infection in León province was similar in all natural regions, probably due to the observation that meteorological conditions are not limiting for the maintenance of the parasite life cycle in any area of the province and to the abundance of irrigated areas together with the lack of planned control strategies.(ABSTRACT TRUNCATED AT 250 WORDS)