All stages in the life cycle of Cryptocaryon irritans were successfully cultured in different medium, without loss of viability. Survival and development of the stage were investigated in selected monophasic media at room temperature, 27oC. Among the three media tested, Hanks' media enhanced the highest rate of encystment and division of trophonts resulting in free moving tomite stages. In contrast Earle's and MEME media only able to support up to encystment stage and no further development stage was determined after that. Cysts maintained in Hanks' medium gave the maximum number of tomites (200-400) through asexual reproduction over an encystment duration of 7 days. The significance of the results is discussed with regard to the routine maintenance of the parasite and hence, the prospects of large scale production in vitro culture for future use.
Keywords: Cryptocaryon irritans, protozoan, in vitro, trophont, tomont, tomite, theront

The enonomic impact of white spot disease, cryptocaryoniasis caused by the protozoan pathogen Cryptocaryon irritans on farmed sea bass has been tremendous and caused much concern in most countries. Hence, there is a need for work on the prevention of this protozoan infection by biologics rather than the recommended administration of chemicals bath (especially formaldehyde) in cultured fish. Most chemotherapy failed since the tomont in an encysting stage is resistant to drugs while the trophonts are often buried deep in the fish tissue. Biological application like vaccination is an effective way to prevent fish diseases. As a preliminary step, there is a need to develop a suitable culture medium that could be used in large-scale production of the parasite for antigen production purposes. In view of that, experimental on the in vitro culture of this parasite was carried out.

The trophonts of C. irritans were collected from the infected hatchery reared sea bass. The infected fish were killed and the gills removed and placed in filtered seawater for the parasites to settle down. Trophonts were collected and rapidly transferred by pipette through three washes in sterile filtered seawater to remove associated host debris and to dilute the bacterial flora. Motile trophonts were selected and subject to three further washes in 10 cm3 of sterile filtered seawater. They were transferred to filtered seawater and some of modify balanced salt solution such as 1x Hanks'(HBSS), Minimum Essential Medium Eagle with Earle's salt without l-Glutamine(MEME) and 1x Earle's