Fish consumption has increased substantially in recent years, and to maintain this sector's expansion, sustainable aquaculture development with adequate measures of quality, sanitation and good management practices is important (FAO, 2020). However, as intensive husbandry systems are implemented, there are health barriers (such as epizootics) that require interventions through therapeutic products . Thus, the use of therapeutics in aquaculture, especially antibiotics, has increased. However, there are many concerns over its effects on the surrounding ecosystems and global health (Liu et al., 2017).Several stress factors, such as sudden temperature variations, water quality and nutrition, handling and high density of organisms in a limited space, can increase their susceptibility to pathogens by for example impairing fish immune defences (Pulkkinen et al., 2010;. To avoid economic losses, many producers opt to use veterinary drugs, disinfectants and other chemical compounds for disease prevention and treatment (Liu et al., 2017). However, despite the many side effects xenobiotics might have in the environment, many countries still lack appropriate use regulations and control (FDA, 2020).Undue administration of chemotherapeutic agents may pose toxic risks to the animals concerned and to manipulators, consumers and nontarget organisms (Rico & Brink, 2014). These
One possible alternative to chemotherapeutic agents in the treatment and prevention of diseases in fish farms is the use of Piper aduncum essential oil. However, ecotoxicological data are required to ensure its proper use and to prevent adverse effects on non-target organisms. These data are relevant since this essential oil is described as having insecticidal, molluscicidal and cytotoxic activitiy that may be associated with its chemical composition. Thus, the aim of this study was to evaluate the ecotoxicity of P. aduncum essential oil to five test organisms using the species sensitivity distribution (SSD) statistical approach. The chemical composition of the essential oil was characterized by means of gas chromatography coupled to mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) for identification and quantitation purposes, respectively. The main component (75.5%) of the essential oil was dillapiole. The hazardous concentration for 5% of biological species (HC5) was calculated to determine the 95% protection level, resulting in a value of 0.47 mg L-1 (with a confidence interval of 0.028 - 1.19 mg L-1. ). A concentration range related to the level of protection for aquatic communities (the predicted no-effect concentration, PNEC) was determined through the application of safety factors to the HC5 value. The ecotoxicity parameters showed that P. aduncum essential oil can be used safely in water bodies at a concentration equal to or below 0.09 mg L-1.
Kudoa is a myxozoan that causes myoliquefaction in marine fishes. Most of species only affect fish, but a K. septempunctata outbreak was reported in 358 people. Although many species of Kudoa are known, none was described in Brachyplatystoma filamentosum, Brachyplatystoma rousseauxii, Mugil curema, Plagioscion squamosissimus or Oxydoras niger until now. Due to the economic cost of eliminating seafood presenting myxozoan lesions, this study aimed to describe lesions found at necropsy and histopathology, as well as to detect this myxozoan by molecular techniques. For this purpose, were sampled 85 fish of the following species: Brachyplatystoma filamentosum, Brachyplatystoma rousseauxii, Mugil curema, Plagioscion squamosissimus, and Oxydoras niger from Colares and Vigia, Pará, Brazil. Necropsies were carried out to describe lesions and molecular techniques (PCR and sequencing) were applied for identification. Although muscle lesions were not observed at necropsy, histopathology revealed bacterial colonies, coagulative necrosis, dystrophic calcification, eosinophils, hemorrhage, parasitic cysts, protozoan, and vacuolization. After sequencing, K. shiomitsui (GENBANK: LC128646) was identified as the causative agent of fishes infection. Also, high parasitism of this myxozoan was observed in fishes sampled, i.e., 90 % in Colares and 100% in Vigia.
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