Efeito do praziquantel sobre as variáveis sangüíneas de Colossoma macropomum Curvier, 1818 (Characidae: Serrasalminae) e sua eficiência como anti-helmíntico no controle de parasitas monogenóides (Plathyhelminthes: Monogenoidea)

Abstract

In order to contribute with research on the use of chemical therapeutics in aquaculture, especially involving native fish species such as the tambaqui, Colossoma macropomum, the present study aimed to evaluate the antihelmintic praziquantel toxic effects on tambaqui through hematological analysis (Chapter 1) and, complementarily, to evaluate its efficacy to control monogenea parasites (Chapter 2). In Chapter 1, bath of 3.12; 6.25; 12.5; 25 and 50 mg of praziquantel/L during 0.5; 1 and 24 hours of exposure were tested. Among the blood parameters evaluated, hemoglobin concentration and mean corpuscular hemoglobin decreased in fish exposed during 24 hr and hyperglycemia was observed on those exposed to the highest concentrations of praziquantel (25 and 50 mg/L) in all bath duration. Results suggest that praziquantel concentrations of 25 and 50 mg/L affect tambaqui homeostasis, regardless the exposing time, and may cause fish mortality. Besides, this study corroborate with the hypothesis that tambaqui aquatic surface respiration (ASR), with the formation of mouth lips, may be stimulated by the reduction of tissue oxygen concentration (hypoxemia), regardless water dissolved oxygen concentration. In Chapter 2, five praziquantel concentrations were tested: 0; 6.25; 12.5; 25 and 35 mg/L in 24 hr baths and blood parameters and fish parasite load were evaluated. In most treatments efficacy was under 60%, except for the treatment with 12.5 mg/L which resulted in 61.8% efficacy. This study indicated that lower praziquantel concentrations were more efficient in controlling the parasites and high concentration of the product induced fish leukocyte alterations comparable to stress, such as lymphopenia, monocytosis, neutrophylia, and hyperglycemia.