The impact on production and mechanisms of pathogenesis of trematode infections in cattle and sheep

Abstract Trematodes can have marked effects on several components of individual animal productivity—particularly growth and wool production, but there is a need for better definition of their effects upon overall flock and herd productivity and of the economic benefits to be derived from their control by chemical, immunological and/or genetic approaches. The reasons for reduced productivity are complex and include reduced appetite coupled with a protein/energy drain arising from increased protein turnover, and in some cases derangements in gastrointestinal function and mineral metabolism are to be anticipated. Knowledge of the effects of trematodes on animal productivity and metabolism lags far behind that of gastrointestinal nematodes and while there is certainly a need for more study of the effects of trematodes per se , there is perhaps an even more pressing need for experimental and field work on mixed infections.