Spatio-temporal and host-dependent variations in prevalence and intensity of heterophyid (Digenea: Heterophyidae) metacercariae infection in brackishwater and freshwater fishes: a comparative study.

Studies on distribution of parasites are important to reveal the ecology of host-parasites interactions. The objective of the study was to compare the variations in heterophyid encysted metacercariae (EMC) infection in freshwater and brackishwater fish hosts and variation in parasitological descriptors of metacercariae infection during different seasons. The status of infection with heterophyid EMCs in the second intermediate host fishes from brackishand freshwater resources was investigated. Seasonal changes in the occurrence of EMCs in different fish hosts were monitored in a longitudinal field survey lasting 12 months from June 2018 to May 2019. Distribution of heterophyid EMCs was found varied in freshwater and brackishwater fishes with higher prevalence in brackishwater fish. There was a distinct seasonal trend in the prevalence of infection for all heterophyid EMCs in the brackishwater fish examined with high burden during summer. Thus variations in parasitic infection among hosts underpin the importance of parasites as an evolutionary or ecological force.