Freshwater fish blood flukes of Sanguinicolidae

This chapter reviews the blood flukes (Sanguinicolidae Poche, 1926), a family of digeneans infecting freshwater ray-finned fishes. Recent revisions based on morphological and nucleotide evidence have redefined this group and its relationship to other fish blood fluke lineages. The life cycle is indirect involving fish definitive hosts and aquatic snail intermediate hosts. Infection causes impairment of respiratory, osmoregulatory and haematopoietic functions, reduced growth and lethargy of young and heavily infected fish. Eggs obstruct gills leading to hyperplasia, ischaemia and necrosis, and haemorrhage when miracidia emigrate from gill tissue. Eggs are sequestered within respiratory and other tissues by granulomatous encapsulation by eosinophils, neutrophils and monocytes/macrophages. Mortalities have been reported from fish farms and hatcheries where infected snails are present, but improvements in husbandry have reduced disease prevalence. Praziquantel is effective in controlling blood fluke infections and is widely used for ornamental fish and under specific veterinary and legislative conditions for food fish.