Fasciola hepatica: a review of the economic impact in cattle and considerations for control.

To understand the rationale behind recommended control programs for liver flukes in cattle, the economic impact and the complex life cycle of Fasciola hepatica need to be appreciated. Fluke-infected cattle rarely demonstrate clinical disease, but subclinical impairment of feed efficiency, growth, and fertility can have an important impact on productivity. Although the precise benefit from controlling liver flukes is unknown due to the inherent variability between studies, most investigations demonstrate a considerable economic advantage to treatment. In addition, recent studies have demonstrated that liver flukes may cause a decrease in host fertility by altering normal metabolism and/or balance of sex hormones. This review focuses on these issues and how to best use available drugs to implement optimal fluke control programs.