In vivo effect of Curcuma longa root crude methanolic extract on health status and mortality of Oreochromis niloticus infested with Ichthyophthirius multifiliis

Abstract

Ichthyophthiriasis is a common ectoparasitic infestation caused by Ichthyophthirius multifiliis. Such infestation brings significant economic losses to Philippine Oreochromis niloticus (Nile tilapia) aquaculture. Plant extracts are explored as alternative treatments with less environmentally-damaging effects. Curcuma longa (turmeric) is one example with proven antiparasitic effect. This study explored the potential activity of turmeric root crude methanolic extracts of two concentrations in treating tilapia with ichthyophthiriasis. Tilapia fingerlings were experimentally infested with I. multifiliis using the cohabitation method and subjects were divided into treatment groups: 20.5 mg/L turmeric, 100 mg/L turmeric, methylene blue (positive control), methanol (solvent control) and no treatment. Tilapia mortalities did not differ across treatment groups (F=1.824, p = 0.177). However, possible synergistic effect of high dosage extract at 100 mg/L and methanol toxicity caused low survival rate of fish in the 100 mg/L turmeric group. The 96-hour LC50 of C. longa extract on tilapia fingerlings was calculated at 30.47 mg/L. The final intensity of infestation for the turmeric extract groups and methylene blue were significantly lower compared to the no treatment and methanol groups (F=40.71, p=0.000). Post-mortem histopathologic examination of integument and gills of tilapia revealed that turmeric-treated fish developed epidermal melanophore accumulation and hyperplastic primary gill lamellae indicating stress response of fish to irritants possibly present in the crude extract. Isolation of active components is recommended to maximize antiparasitic activity and improve survival of fish.