Efeito do fluazuron sobre ovos, larvas e fêmeas ingurgitadas de Rhipicephalus microplus

Abstract

The objective of this research was to evaluate the effect of the arthropod growth regulator fluazuron in the energetic metabolism of Rhipicephalus microplus. 6 stabled cattle divided into control and treated groups containing three animals each. A commercial formulation containing the active compound fluazuron was administered topically in the treated group. The engorged female ticks were collected from some days before (day 0) and after treatment of animals (4, 8, and 15 days). After collecting the engorged females, the following biological parameters were analyzed: weight of the engorged female, weight of the female after oviposition, laying period, laying weight, egg production rate, reproductive efficiency index, percentage of hatching and nutritional index. It was also evaluated the metabolic profile: in the hemolymph (concentration of glucose, total protein and organic acids - oxalic, pyruvic and lactic, enzymatic activity of LDH, ALT and AST); in the fat body (glycogen concentration and percentage of variation of neutral lipids); in eggs (concentration of glucose and total protein content, percentage change of neutral lipids and enzymatic activities of ALT and AST); and in the cuticle of engorged female ticks (percentage change of neutral lipids). Secondly, female immersion test was conducted to assess the activities of carboxylesterases enzymes, monooxygenases (MFO) and glutathione-S-transferase (GST) in sensitive strain of eggs and larvae (Porto Alegre, RS) compared with resistant strain (Jaguar, RS). It also assessed the detoxification enzymes in the fat body of engorged females of sensitive strain. The results showed that all the biological parameters showed lower results when compared to the control group after the exposure to fluazuron, except the weight of the female after oviposition. Although an increase was observed in the concentration of glucose in hemolymph on the 8th day and glycogen in the fat body in 15th day, there was no significant difference in the comparison of means between control and treated day-to-day. The concentration of lactic acid gradually increased in the treated group over time due to treatment, indicating increased anaerobic metabolism. There was no significant difference in the percentage change of neutral lipids in fat body, cuticle and eggs in any of the time intervals. No significant difference was observed in the activity of transaminases in the hemolymph, but it was observed in eggs after the treatment on the 8th day. The activity of MFO was higher in the comparison between the resistant and sensitive strains in eggs, but in larvae, the increase was observed in carboxylesterases in the resistant strain. In females, MFO showed high activity in the fat body as a function of fluazuron exposure, especially on day 4 in the treated group. Increases in transaminase activity and detoxification enzymes in females and eggs were associated with possible cell damage and trying to metabolism of active principle-tested. For the first time, a research about the metabolic effects of fluazuron has been conducted, focusing on different biochemical aspects, demonstrating that its effectiveness is related to a number of metabolic changes, leading to a parasite homeostasis breaking.