Mucosal immune responses to Ichthyophthirius multifiliis in the ocular mucosa of rainbow trout(Oncorhynchus mykiss,Walbaum),an ancient teleost fish

The eye,as a specialized visual organ,is directly exposed to the external environment,and,therefore,it faces constant chal-lenges from external pathogenic organisms and toxins.In the ocular mucosa(OM)of mammals,mucosal-associated lymphoid tissues(MALTs)constitute the primary line of defense.However,the immune defense role of the OM remains unknown in aquatic vertebrates.To gain insights into the immune processes within the OM of teleost fish,we developed an infection model of rainbow trout(Oncorhynchus mykiss)OM using a parasite,Ichthyophthirius multifiliis(Ich).Immunofluorescence,qPCR,and H&E staining revealed that Ich successfully infiltrates the OM of rainbow trout,leading to pathological struc-tural changes,as evidenced by A&B staining.Importantly,the qPCR results indicate an up-regulation of immune-related genes following Ich infection in the OM.Moreover,transcriptome analyses were conducted to detect immune responses and impairments in eye function within the OM of rainbow trout with Ich infection.The results of the transcriptome analysis that Ich infection can cause an extensive immune response in the OM,ultimately affecting ocular function.To the best of our knowledge,our findings represent for the first time that the teleost OM could act as an invasion site for parasites and trigger a strong mucosal immune response to parasitic infection.

First report of Ichthyophthirius multifiliis (Ciliophora:Oligohymenophorea) from Aphanius dispar (Cyprinodontidae) in Iran

Objective:To determine the infection of Aphanius dispar(A.dispar)by Ichthyophthirius multifiliis(I.multifiliis)in Iran.Methods:A total of 97(22 males and 75 females)individuals were collected using dip net from Mehran River,Hormuzgan Province,South of Iran in January 2008.Total length,standard length and weight of the collected specimens were measured to using vernier caliper.Whole body of fish was examined macroscopically for the presence of any blister.For the detection of Ichthyophthirius,the mucus was scraped gently from skin onto a micro slide and stained by Azo-carmine.Prevalence,intensity and abundance of parasite were analyzed.Results:In this study 50(51.55%)specimens including 12 males and 38 females were found infected with I.multifiliis which is an obligate protozoan parasite of freshwater fishes with a direct life cycle and it causes weight loss and mortality in fishes.The infection is known as ichthyophthiriasis or white spot disease,one of the most serious diseases in freshwater fishes.Prevalence,intensity and abundance of parasite in female and male fishes were 50.67%,29.26,14.83 and 54.55%,18 and 9.82,respectively.No sex preference and predilection of body site as microhabitats for this parasite in A.dispar,as well as in three length groups of fish standard length ranging 18-23 mm,23-28 mm and 28-34 mm.However,prevalence and abundance are significantly increased in larger fish than smaller one.Conclusions:This is the first report of I.multifiliis(Fouquet,1876)from A.dispar in Iran and this fish is considered as a new host for the parasite.