Efficacy of antiparasitic agents combined with soy lecithin in mullet (Mugil liza), in controlling metazoan parasites

Author: Kamila Oliveira dos Santos (Currículo Lattes)
Supervisor: Dr Joaber Pereira Junior
Co-supervisor: Dr Rogério Tubino Vianna


The mullet, Mugil liza is inserted among the species with growth and market potential in Brazilian marine fish farming. However, difficulties are encountered in the sense of preventing and treating diseases present in animals in the breeding system. The use of chemotherapeutic drugs has been a common practice for disease control in fish farms and may be feasible when the correct dosage and time of exposure of the drug are used. In the therapeutic control of parasitic diseases, short and long term baths have been a common practice. However, in treatments via baths with drugs with low water solubility it is difficult to apply. Praziquantel (PZQ) and mebendazole (MBZ) are drugs indicated for the control of parasitic diseases in human and veterinary medicine.In fish, the efficiency of these drugs has been reported through different species and methods of application. However, due to the low solubility in water, the application of these drugs in the form of baths is difficult. Lecithin is a phospholipid extracted from egg yolk or soybeans and its main component is phosphatidylcholine, which can act in several ways, such as dispersants, stabilizers, solubilizers of pharmaceutical forms. Soy lecithin is considered a good vehicle for lipophilic drugs, being a solid form dispersant in the liquid. Therefore, the aim of this study was to determine the effectiveness of PZQ and MBZ combined with soy lecithin (LS). For that, the fish were collected in the stream of the ship (32º 29 '48 ”S; 52º 26' 74” O) and kept in the Laboratory of Biology of Parasites of Aquatic Organisms.The lethal mean concentration test (LC50-24 h) was carried out, the survival rate was checked, the percentage of efficacy and the water quality parameters were monitored. Necropsies of 40 fish were performed to determine the presence of parasites and their parasitological indexes. The CL50-24 h test for PZQ and MBZ combined with LS, was performed in the following concentrations: Control, LSA, 0.5; 1.5; 2.5; 5.0; 7.5; 10.0 mg/L and control, LS, 0.5; 1.0; 2.0; 3.0; 5.0; 7.0; 9.0; 12.0 mg/L, respectively, 30 fish per concentration. Three effectiveness experiments were carried out with the PZQ: control, LSA, 0.5; 1.5; 2.0 mg/L baths of 30 minutes and 24 hours, respectively. The same concentrations were also tested in 24-hour baths without the presence of alcohol in the dilution of the PZQ.The definitive test with MBZ consisted of three concentrations 4.0; 8.0; 12.0 mg/L, zero control and the control group with LS (2.0 mg/L). All experiments were completely randomized and in xiii three simultaneous repetitions. The analyzes of parasitological data were made using the Quantitative Parasitology program, the other statistical analyzes consisted of the analysis of variance (ANOVA), followed by the Tukey test, with the sigmaStat 3.5 statistical program at 5% probability. There were occurrences of Ligophorus uruguayense and Solostamenides platyorchis and digenetics in the juvenile mullet gills, with a prevalence of 42.5%; 30% and 20%, average intensity of infection/infestation (3.5, 2.0 and 2.3), average abundance of infection/infestation (1.5, 0.6 and 0.45), respectively. It was not possible to determine the LC50-24 h for both drugs.The water quality parameters showed no statistical difference. The survival rate was greater than 90% in 30 minutes and 24 hours of bathing with the PZQ and greater than 80% in bathing with the MBZ. There was no effectiveness of the PZQ after 30 minutes of bath for L. uruguayense, but it was effective with a percentage above 70% in 0.5; 1.5; 2.0 mg/L against S. platyorchis, against digenetic 0.5 mg/L was effective in 83.3%. After 24 hours of bath with PZQ diluted in alcohol and combined with LS 2.0 mg/L, it was effective against L. uruguayense. After 24 hours of bathing with PZQ and LS without alcohol, L. uruguayense was 59% and 76.7% effective at 1.5 and 2.0 mg/L, respectively. MBZ was 74.5% effective at 4.0 mg/L against L. uruguayense and 100% at all concentrations against S. platyorchis and digenetics