Effect of gamma irradiation on inactivation of Ichthyophthirius multifiliis trophonts and its efficacy on host response in experimentally immunized rainbow trout (Oncorhynchus mykiss)

Abstract

IntroductionThe freshwater ciliate Ichthyophthirius multifiliis (I. multifiliis), one of the most important protozoan pathogens of farmed and wild fish populations, causes significant economic losses to aquaculture industries worldwide (1). The 3 stages in the life cycle of the parasite are an infective theront, a parasitic trophont, and a reproductive tomont (2). It is difficult to control this parasite using chemotherapy after penetration into fish skin and gills. The high cost involved in therapy and the public concern for food and environmental safety are other disadvantages of chemotherapy. Thus, vaccination against I. multifiliis can be considered an alternative to chemical treatments to prevent mortality (2) in fish. A number of studies have indicated that whole-cell trophonts, theronts, and ciliary protein preparations or recombinant i-antigen proteins of this parasite are able to induce an acquired immune response in numerous fish species, including the channel catfish (Ictalurus punctatus), trout (Salmo gairdneri), and carp (Cyprinus carpio) (2-5). Trophonts are commonly inactivated by using 1%-4% formalin (5) or freezing (5) and used for immunization at different doses (5).Gamma radiation is widely used by many researchers to inactivate parasites for the preparation of vaccines, instead of traditional thermal or chemical methods of inactivation. This technology appears to create a vaccine that is more effective than so-called "killed" vaccines against disease, and has the added advantage of a longer storage life than "live" vaccines. Irradiation is a technically simple process that retains the structural features of the microbial pathogen without destroying the natural antigens or the intrinsic adjuvant. Therefore, a strong immune response

Variations of kidney, liver and spleen total sialic acid levels in immunized rainbow trout (Oncorhynchus mykiss) against Ichthyophthirius multifiliis

“…The fish were kept for 5 days at 20 °C and the trophonts were then collected with a 200-mesh sieve (skin). Trophonts should be used immediately (HEIDARIEH et al, 2014a).…”

“…A dose of gamma ray (170 Gray) was used for irradiation of the parasite samples. The irradiation process was performed on parasite samples held on dry ice (HEIDARIEH et al, 2014a).…”

Differential MHC-П, IL-8 and IgM genes expression in the liver, head Kidney and gill tissues of juvenile rainbow trout (Oncorhynchus mykiss) immunized by inactive trophonts of Ichthyophthirius multifiliis

“…Gamma-irradiated trophonts were prepared as described previously (17) . Trophonts of 956 I. multifiliis used in this study were obtained from an infected pet fish.…”

Histopathological evaluation of in vitro Ichthyophthirius multifiliis culture in Red koi (Aka Matsuba) tissue

“…Mature trophonts were collected and transferred to glass aquaria containing aerated tap water at 17-18 °C until all individuals were heavily infected by the ciliate parasite. After 72 h the trophonts in infected fish were collected and counted to prepare vials containing 10 trophonts in each vial (Heidarieh et al, 2014).…”