Antiparasitic, physiological and histological effects of the essential oil of Lippia origanoides (Verbenaceae) in native freshwater fish Colossoma macropomum

Abstract

This study examined the in vitro and in vivo, histopathological, anti-parasitic and hematopathological effects of the essential oil of Lippia origanoides on Colossoma macropomum. Essential oil concentrations of 10, 20, 40, 80, 160 and 320 mg•L −1 were tested in vitro against monogenoideans (Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri) from the gills of C. macropomum. Concentrations of 320 and 160 mg•L −1 were 100% effective against these parasites within 20 and 60 min of exposure, respectively. The 80 mg•L −1 concentration was approximately 80% effective with 3 h of exposure, reaching 100% with 6 h of exposure. The 40 mg•L −1 concentration was also 100% effective with 6 h of exposure. The other concentrations were only weakly effective in vitro. Parasite mortality in controls (water or water + alcohol) began after 3 h, with 100% mortality after 8 h. In vivo tests, in which fry of C. macropomum were placed in baths with 20 mg•L −1 of the essential oil for 60 min, and 40 mg•L −1 for 30 min, did not lead to reductions in parasite abundances. In addition, the essential oil had an anaesthetic effect on fish, increased total protein levels, increased monocyte and neutrophil numbers, and reduced haematocrit. Slight to moderate and severe damage was observed in the gills of C. macropomum fingerling immediately after exposure to the essential oil, and 24 h after the treatments were applied, with no difference between treatments. Histological changes observed in the gills after exposure to concentrations of 20 and 40 mg•L −1 of L. origanoides essential oil were: hyperplasia and fusion of the lamellar epithelium, capillary dilation, displacement of the lamellar epithelium, and lamellar aneurism and epithelial rupturing with haemorrhaging. Oedema, mucous and chloride cell proliferation, lamellar hypertrophy, congestion and necrosis were less frequently observed. It can be concluded that the essential oil of L. origanoides was dose-dependent in vitro effect against monogenoidean parasites of C. macropomum. Unfortunately, the low concentrations tolerated by the fish in the vivo assay (20 and 40 mg•L −1) was not effective. Statement of relevance: The manuscript represents original research on use of the essential oil of Lippia origanoides against ectoparasites of Colossoma macropomum, an important finfish of Amazon region. This manuscript includes treatment in vitro against monogenoideans, and in vivo against protozoans and monogenoideans. Besides, histopathological and hematological analysis of the fish exposed to different concentrations of L. origanoides, a medical plant from North, Central and South America, were performed.

Current knowledge on use of essential oils as alternative treatment against fish parasites

“…Thus, we recommend that threshold points should be established, below which the efficacy of EOs for fish parasite control should not be considered. We also suggest that such threshold points should be around 70% (Soares et al, 2017b).…”

Nanoemulsion from essential oil of Pterodon emarginatus (Fabaceae) shows in vitro efficacy against monogeneans of Colossoma macropomum (Pisces: Serrasalmidae)

“…Brazilian production of this species through aquaculture in 2014 was approximately 140,000 tons (IBGE, ; Valladão et al., ). However, one of the major problems in intensive farming of C. macropomum is infection caused by Anacanthorus spathulatus , Notozothecium janauachensis and Mymarothecium boegeri (Monogenea), which may compromise production (Soares et al., ; Cardoso et al., ; Soares et al., ).…”

“…Essential oils are secondary metabolites produced by medicinal plants that can be extracted from a variety of plant sources. They are used for many purposes in the pharmaceutical and food industries (Anwer, Jamil, Ibnouf, & Shakeel, 2014), and for controlling and treating ectoparasites of fish (Zhang et al, 2014;Hashimoto et al, 2016;Soares et al, 2016;Valladão et al, 2016;Soares et al, 2017;Costa et al, 2017). Thus, use of medicinal plants has been increasing within aquaculture worldwide, given that these plants are easy to cultivate, have biodegradable action, do not give rise to accumulations in animal tissue and present low toxicity (Coimbra, Soares, Garrido, Sousa, & Ribeiro, 2006).…”

“…Thus, use of medicinal plants has been increasing within aquaculture worldwide, given that these plants are easy to cultivate, have biodegradable action, do not give rise to accumulations in animal tissue and present low toxicity (Coimbra, Soares, Garrido, Sousa, & Ribeiro, 2006). However, it has been reported that the low dispersion of essential oils in water makes it difficult to use them in aquaculture (Hashimoto et al, 2016;Soares et al, 2016;Soares et al, 2017;Costa et al, 2017). Therefore, methods for facilitating their dispersion are required so that they can be used in therapeutic baths for fish.…”

“…However, one of the major problems in intensive farming of C. macropomum is infection caused by Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri (Monogenea), which may compromise production (Soares et al, 2016;Cardoso et al, 2016;Soares et al, 2017).…”