Assess the impact of parasitic infections on blood factors, immunity and stress and gill tissue of silver carp (Hypophthalmichthys molitrix)

Due to silver carp fry mortality in Rasht city from April to August 2017, 90 fish from 3 farms were sampled.  Samples collected from 3 pools in each farm. They were included 1- infected to parasite, 2- Blood samples were taken to measure blood factors, immunity and stress. Blood samples were collected using caudal fin cutting to measure blood factors, immunity parameters, and stress factor. Then fish weight and length were measured. Also parasitology and gill histology examinations were done. Diplostomum spathaceum, Dactyloyrus sp, Chilodonella sp and Trichodina sp were find in fish samples.  In fish belong to unknown syndrome group, just Dactylogyrus was seen. The highest WBC, RBC, Hb, Hct, lysozyme and total immunoglobulin were seen in group with unknown causes, also the highest Glucose and Cortisol were seen in infected group and the highest Igm was seen in safe group. Histology studies showed the most gill injuries in infected group and group with unknown causes. Moreover, parasites were included Dactylogyrus, Trichodina and Trichopyra. Also Dactylogyrus and Desmocystidium spore were observed in group with unknown causes.  Totally, the results should that silver carp health status is influenced by fish parasites.