Evaluation of three different methods for control of monogeneans and Capillaria sp. (Nematoda:Capillariidae) parasites of angel fish (Pterophyllum scalare Liechtenstein, 1823)

Abstract

The aim of this assay was to evaluate three methods for control of helminth parasites of angel fish fry. Fifteen young were used for the initial parasites counts: the average number of monogeneans in the gills was 50 ± 28, and that of nematodes in the intestine was 14 ± 9. Statistical test was used following randomized delineation (RD) with four treatments and 15 replicates for the parameters of average infestation, and a RD of four treatments and three repetitions for the prevalence parameter. The used treatments were: T1 - consisted in change of fish from one to another aquarium; T2 - fish fed with ration containing 1,000 mg of levamisole/kg+2,000 mg of praziquantel/kg, with aquarium change; T3 - fish submitted to aquarium change and treatment (bath) with 15 mg of formalin (37%) per liter of water for 6 alternated days; and the Control. The analysis of the results shows that the aquarium change and the treatment with formalin decrease the number of monogenean parasites (p < 0.01); however, significant differences with relation to the prevalence of this parasite were not found, demonstrating that although the decrease of the number, it was present in all fish. For nematodes, significant decrease in the number was observed (p < 0.01) in the fish treated with ration containing levamisole and praziquantel, and the decrease of prevalence can also be verified in the aquarium change and ration treatments, meaning that some fish did not present the parasite after the treatment. In conclusion, the treatment with formalin was efficient for the monogenean parasites control, however a constant accomplishment is necessary, since even after the treatment the fish presented the parasites, and the treatment with ration was efficient for the nematodes control. It was still verified that the change of aquarium allowed a smaller number of parasites, indicating there were a smaller infestation rate due to the break of the parasite life cycle.