Anti-dactylogyridean efficacy of solid lipid nanoparticles of Pentaclethra macroloba oleoresin in Colossoma macropomum, with hematology and gill histopathology assessment.

Abstract

This study investigated, for the first time, the efficacy against Anacanthorus spathulatus, Notozothecium janauachensis, and Mymarothecium boegeri of solid lipid nanoparticles (SLNs) containing Pentaclethra macroloba oleoresin, and the effects of therapeutic baths on the hematology (glucose, total proteins, and erythrocyte parameters) and gill histopathology of tambaqui Colossoma macropomum. The oleoresin used had a predominant composition of monounsaturated fatty acids in their composition, with oleic acid present at a relative abundance of 56.4% and behenic acid present at 15.8%. Tolerance trials with different concentrations of SLNs (500, 750, 1,000, and 2,000 mg/L) showed that the fish could tolerate 500 mg/L. This concentration was used for the five 1-h therapeutic baths per day. Two control groups were also used: one with water from the culture tank and the other with Tween 80 + myristic acid. The therapeutic baths' efficacy against dactylogyridean parasites was similar between the group with SLNs containing 500 mg/L of P. macroloba oleoresin and the control group with Tween 80 + myristic acid. The therapeutic baths only increased plasma total protein levels. Histopathological analyses of tambaqui gills showed moderate changes that did not affect respiratory function in fish subjected to baths with SLNs containing P. macroloba oleoresin. Although the fish could tolerate 500 mg/L of SLNs with P. macroloba oleoresin without experiencing adverse physiological effects, this treatment was therapeutically ineffective. The factors responsible for this ineffectiveness were discussed.