AbstractEighty-six percent (230 out of a total 268) of the cows on a Dorado dairy farm were found positive to F. hepatica on coprological examination. The highest infestation rate of 95.4% was determined in the older animals in the herd (9 to 12 yr old) while the lowest rate of 71.3% was in the younger (3 to 3 1/2 yr old) animals. L. cubensis, the predominant snail intermediate host for F. hepatica on this particular farm, is a relatively dynamic organism that has a potential life-cycle (egg to egg) of 21 days. The number of snail habitats, the number of snails, and the percentage of F. hepatica-infested snails noticeably increased during the winter months of December, January, and February, when there was high average monthly rainfall of 145 mm and low average monthly temperature of 24°C. Cattle in the Dorado area acquire F. hepatica infestation only during certain months of the year, that is, from November to February. This finding disproves the assumption of year-round infestation. An increase in the quantitative serum glutamic oxalacetic transaminase analysis (SGO-T) of cattle in an endemic area is important since it may indicate that the animals may have been exposed to F. hepatica infestation. No effective control of fascioliasis in dairy cows in Dorado is recommended except sanitation and good nutrition.
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