Albendazole is effective for controlling monogenean parasites of the gills of Piaractus brachypomus (Serrasalmidae) and Megaleporinus macrocephalus (Anostomidae).

Monogenean infestations can cause high mortality in farmed fish and therefore significant economic losses. The present study investigated the efficacy of albendazole in therapeutic baths against monogeneans of Piaractus brachypomus Cuvier, 1818 and Megaleporinus macrocephalus (Garavello & Britski, 1988). For both fish, a 24 hours therapeutic bath with albendazole concentrations of 150, 300 and 500 mg/L were tested against monogeneans from the gills. The baths had an efficacy from 61.4 ± 32.9 (95%CI=64.5) against monogeneans of P. brachypomus, and from 95.4 ± 5.6 (95%CI=10.9) against monogeneans of M. macrocephalus. In P. brachypomus, the hepatosomatic index (HSI) in fish exposed to 150 mg/L of albendazole was higher than in fish exposed to 300 mg/L. The splenosomatic index (SSI) values in fish exposed to 150 mg/L of albendazole were lower than in fish exposed to 300 mg/L. In M. macrocephalus, the HSI and SSI values decreased in treatments with 150, 300 and 500 mg/L of albendazole to control and treat infestations by monogeneans. For M. macrocephalus, 150 mg/L of albendazole can be used to control and treat infestations by monogeneans, while for P. brachypomus 500 mg/L of albendazole can be used in a 24 hours bath.