Comparison of various treatment methods of ichthyophthiriosis and their efficacy (in vitro) on live theronts in common carp

Objective: Severe infections of fish by parasitic ciliate, Ichthyophthirius multifiliis (ich), particularly in fish grown commercially under intensive conditions, can result in high mortality in affected populations and concomitant economic loss. Malachite green along with formalin commonly have been used as the most efficient treatment strategy for ich. Since, there were some reports on teratogenic effect of malachite green, this treatment has been prohibited in aquaculture industry. In this study, effect of benzalkonium chloride on Ichthyophthirius theronts (infectious stage of ich) infecting common carp were investigated and compared with conventional substances. Method & Materials: 100 juvenile common carps were divided into 5 similar groups and treated with formalin (group 1), formalin and malachite green (group 2), formalin and benzalkonium (group 3), benzalkonium (group 4) and control without any treatment (group 5). Dosage and treatment duration were chosen according to conventional treatment strategies. Mortality rate of fish in each groups were recorded for one month. The efficacy of each treatment, including killing and immobilizing effect on theront was measured. Results & Conclusion: Results showed that the survival rate after one month in groups 1, 2, 3, 4 and 5 were 75%, 65%, 60%, 85% and 100%, respectively. Benzalkonium showed minimum mortality. Results of in vitro efficacy assay showed some differences among groups. Alive theront per ml after treatment in groups 1, 2, 3, 4 and 5 were 212/5 74/2,537/5 53/2,87/5 35/02,225 61/93,925 55/87, respectively. It can be concluded that conventional therapeutic method for treatment of fish (formalin 1:40,000 and malachite green 0/2mg/l) had the least efficacy on theront (in vitro) compare to other methods (P<0.05), while there was no significant difference among other groups (P>0.05). In addition, benzalkonium had proper efficacy and could be used as an alternative to malachite green. However, it induced high mortality (40%) when used with formalin. Therefore, benzalkonium chloride can be used along with other therapeutic substances except formalin.

کلیدواژه ها:

Treatment ، Ichthyophthirius multifiliis ، Common carp