The in vitro and in vivo effect of tannic acid on Ichthyophthirius multifiliis in zebrafish (Danio rerio) to treat ichthyophthiriasis.

Abstract

The in&#xa0;vitro antiparasitic effect of polyphenol tannic acid (TA) on Ichthyophthirius multifiliis theronts and tomonts was evaluated. In vitro antiparasitic assays revealed that TA in a dose- and time-dependent pattern through the damage of parasite plasma membrane could be 100% effective against I. multifiliis theronts at concentrations of 8 and 11&#xa0;ppm during all the exposure times (45-270&#xa0;min). The tomonts proliferation was completely inhibited by penetrating TA (at least 15&#xa0;ppm for 22-hr exposure) into encysted tomont across the cyst wall. However, 10&#xa0;ppm TA could result in a ninefold decrease in the population of live tomonts compared to the control group (p&#xa0;<&#xa0;0.05). Although at theront concentrations of over 6,000 per zebrafish (Danio rerio), a 100% prevalence of ichthyophthiriasis during a 5-day exposure was recorded, results of in&#xa0;vivo tests showed that the parasite that pretreated up to 10&#xa0;ppm TA for 70&#xa0;min had not any capability to infect the studied zebrafish population. The acute toxicity (96&#xa0;hr-LC) of TA for zebrafish was 19.51&#xa0;ppm. Thus, TA can be considered as a natural therapeutant to safely and efficiently improve the health of aquatic systems by controlling ichthyophthiriasis.