Molecular remedies against Cryptocaryon irritans Brown, 1951—Practical difficulties

Abstract

This review paper deals with the immunological response in marine fish infected by Cryptocaryon irritans and discussed the practical difficulties in the development of potential molecular remedies. Browsing through the literature, it is understood that the development of molecular diagnostic tool to detect the early infection in fish by C. irritans is under progress. Once it is successfully established, the possible application of this technique could be suggested for even the non‐specific treatments such as copper‐based medications and bare‐bottomed quarantine of culture tanks. However, prior protection of healthy fish from C. irritans could be accomplished through proper immunization by infective theronts. In this case, a well‐suited in vitro culture technique is necessary to harvest theronts in large scale. Recent immunological and transcriptome studies predicted that the components related to local immune response are more effective against C. irritans than their systemic counterparts. However, in vivo experiments to prove the effect of these antiparasitic molecular components are meagre. Though molecular vaccines, developed from the well‐characterized 34 kDa immobilization antigen (iAg), responded well, these remedies fail to have a uniform impact against antigenically different strains (serotypes). More research is recommended to identify common protective epitopes from different serotypes. Also, studying the adjuvant effects of various innate responsive components like cytokines is significant. The suggested studies would be immensely helpful to develop effective vaccines against C. irritans infection and thereby optimize the aquaculture practices.

Host responses against the fish parasitizing ciliateCryptocaryon irritans

“…Non‐specific immunity provides the first line of defense against invading pathogens and it has been extensively studied 25 . C. irritans infection can induce a robust non‐specific immune responses for the ultimate survival of the infected host 26 . The pro‐inflammatory cytokine and chemokines produced by non‐specific immune responses, will further activate the T and B cells‐mediated specific immune responses to inhibit growth of parasites and mediate its clearance.…”

Treatments of orange‐spotted grouper (Epinephelus coioides) against Cryptocaryon irritans with •OH, ClO2 or HCHO: Survival, physiological and histological response

“…However, some treatments negatively affected fish health, fish product safety and the marine environment, along with some other issues (Daer et al, 2021; Silva et al, 2011; Song et al, 2018; Wang et al, 2018). Hyposalinity immersion and transfer of the cultured zone are effective for controlling C. irritans ; however, they are not feasible for large‐scale fish culture or debilitated fish (Jose Priya & Sudha, 2020). Formalin (HCHO) is widely used against different parasites such as C. irritans , Ichthyophthirius multifiliis and Mesanophrys spp.…”