Over the last two decades, the global aquaculture industry has been highly successful, and continues to grow while achieving the critical objective of environmental, economic, and societal sustainability. Aquaculture is the fastest-growing food production sector in the world, and globally accounts for more fish biomass than capture fisheries, if non-edible amounts are included, and more total biomass than beef (Boyd et al. 2020; Tavares-Dias, 2021). Due to a decline in wild capture fisheries, aquaculture is a crucial component of future food security, and is essential to meet the demands of a human population expected to grow to nearly 10 billion by 2050 (Huston et al. 2020). Aquaculture is often regulated by national agencies, which represent a legal interpretation of local environmental sustainability. In Brazil, the total freshwater fish production of fish farming in 2021 was 841,005, representing an increase of 4.7% compared to 2020. In the last eight years, this production activity has grown 45%, equivalent to an average of 5.6% per year (PEIXEBR, 2022). Hence, Brazil occupies 13th place in global aquaculture fish production, and is eighth in the global inland aquaculture production of finfish (Cavalli et al. 2021).
Among the native fishes that have been cultured in Brazil are Piaractus brachypomus (Serassalmidae) and Leporinus macrocephalus (Anostomidae). An easy acceptance of commercial feed and their fast growth have encouraged the increased production of these fish species in some regions of country. Farmed in commercial fish farms, these fish are routinely stressed by intensive production management practices, leading to the emergence of parasitic diseases that naturally occur in the aquatic environment. Hence, parasitic diseases are most common in the farming of these fish species and are among the factors that strongly interfere with their growth (Martins et al. 2017; Negreiros and Tavares-Dias 2019; Negreiros et al. 2021). Among the main taxa of disease-causing parasites in P. brachypomus (Negreiros and Tavares-Dias 2019) and L. macrocephalus (Martins et al. 2002; Martins et al. 2017; Negreiros and Tavares-Dias 2021) are helminths monogeneans.
Monogeneans are parasitic helminths with a short, direct life cycle, the vertical transmission of which facilitates infection levels in intensive fish farming that cause several disorders in the animal (Alves et al., 2019); such as the excessive production of mucus in the skin and gills, as well as hyperplasia, edema, the fusion of the secondary lamellae, and branchial necrosis (Tavares-Dias et al. 2021). Furthermore, secondary lesions caused by other pathogens, such as fungi and bacteria can result. Therefore, such problems show that although Brazil has an important role in the production of food from aquatic animals, the industry of fish farming yet faces many challenges.
The management and control of infections caused by monogeneans poses a constant challenge for fish farming, as it is greatly complicated by the limited availability of licensed anthelmintic drugs, with varying degrees of effectiveness (Alves et al. 2019). In addition, the many chemical drugs that have been used against these parasites present certain problems, such as low efficacy, solubility and specificity, toxicity to host, and resistance (Santamarina et al. 1991; Tojo et al. 1992; Buchmann et al. 1992; Forwood et al. 2013; Alves et al. 2019; Tavares-Dias 2021). Despite the broad-spectrum and tolerance of benzimidazole albendazole (ABZ), to our knowledge, it has only been employed for the control and treatment of infections caused by monogeneans in Anguilla anguilla (Buchmann and Bjerregaard, 1990), Onchorhynchus mykiss (Tojo et al. 1992), Piaractus mesopotamicus (Onaka et al., 2003) and Colossoma macropomum (Alves et al. 2019). Albendazole is a versatile anthelminthic that is rapidly oxidized to its pharmacologically active metabolite, albendazole sulfoxide, after administration. Since it is widely used around the world, despite it has not yet been regulated for application in fish farming, this anthelmintic has been studied (Cordeiro et al. 2022). However, it has not been assayed to determine its efficacy in controlling monogeneans of P. brachypomus and L. macrocephalus, both fish of great economic importance to aquaculture in Brazil. Thus, the purpose of this study was to investigate the efficacy of albendazole in therapeutic baths against monogeneans of P. brachypomus and L. macrocephalus.