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

Abstract

-This review article focuses on current knowledge about in vitro and in vivo experimentation relating to use of essential oils (EOs) to combat fish parasites. In addition, we discuss the existing methodologies used in studies to determine the antiparasitic activity of EOs, along with their toxicity and major compounds. The methodological approaches used to describe the anthelmintic properties of EOs were demonstrated. The consistency of their activity and thus their potential use for fish ectoparasites (in vitro and in vivo) and endoparasites (in vitro) control was reviewed. There is a clear need to find EOs and active agents of EOs to treatment in vivo against endoparasites of fish. Thus, progress may be achieved through considering the beneficial aspects of EOs when their complementarity and potentiality are exploited. EOs are therefore viable alternative sources of therapeutic products against fish parasites. On the other hand, use of chemotherapeutics has been increasingly questioned, such that constant environmental and consumer concerns regarding them now exist. The synergistic functions of EOs, in comparison with the action of one or two major compounds of these oils, seems unquestionable. It is possible that their activity is modulated by several molecules of the major compounds. Lastly, EOs are bioactive products that are viable sources of therapy against fish parasites. Although more than 3000 EOs are known, less than 0.4% of them have been tested on fish parasites. Thus, it has become clear that more studies testing these therapeutic alternatives are required, in order to evaluate the antiparasitic potential of other EOs for controlling fish parasites and to maximize their benefits to hosts.

Nanoemulsions with oleoresin of Copaifera reticulata (Leguminosae) improve anthelmintic efficacy in the control of monogenean parasites when compared to oleoresin without nanoformulation

“…Phytotherapeutics have higher efficacy and lower toxicity when compared to chemotherapeutics and are considered as an alternative treatment in fish farming for the control of infections caused by monogeneans, which are the most prevalent parasites. Phytotherapeutics include oleoresins, essential oils and their metabolites with antiparasitic properties against monogeneans in fish (Costa et al, 2017; Tavares‐Dias, 2018; Valentim et al, 2018b).…”

“…Therefore, global expansion of fish farming must include continuous monitoring of parasitic infections and development of treatments (Valentim et al, 2018a), specifically with the use of effective and functional phytotherapeutics to manage outbreaks of monogeneans. The use of phytotherapeutics based on nanotechnology has been suggested to facilitate the control of these ectoparasites in fish farming (Tavares‐Dias, 2018; Valentim et al, 2018a, 2018b).…”

“…(Arruda et al, 2019; Trindade, Silva, & Setzer, 2018), including anthelmintic activity against monogeneans in fish (Costa et al, 2017; Valentim et al, 2018b). Hence, there exists a growing interest in the use of oleoresins and essential oils and their bioactive compounds for treating fish infected by monogeneans (Luis et al, 2019; Morales‐Serna et al, 2019; Tavares‐Dias, 2018). However, oleoresins and essential oils have low water solubility and low bioavailability, which are major disadvantages for use in fish farming (Costa et al, 2017; Tavares‐Dias, 2018; Valentim et al, 2018a, 2018b).…”

“…Hence, there exists a growing interest in the use of oleoresins and essential oils and their bioactive compounds for treating fish infected by monogeneans (Luis et al, 2019; Morales‐Serna et al, 2019; Tavares‐Dias, 2018). However, oleoresins and essential oils have low water solubility and low bioavailability, which are major disadvantages for use in fish farming (Costa et al, 2017; Tavares‐Dias, 2018; Valentim et al, 2018a, 2018b). Thus, the administration of phytotherapeutics using a nanoemulsion‐based delivery system may increase their effective use in the control of monogeneans in fish.…”

“…Nanoemulsions are generally oil‐in‐water‐type substances, such as an oily (dispersed) phase and aqueous (dispersing) external phase, allowing lipophilic substances to be solubilized in water (Valentim et al, 2018a, 2018b). Such nanoformulations may improve water solubility of oleoresins and essential oils, thereby increasing therapeutic potency and reducing toxicity of phytotherapeutics when treating fish infected by monogeneans (Tavares‐Dias, 2018; Valentim et al, 2018a, 2018b). In Rhamdia quelen , it has been demonstrated that the nanoencapsulation of Melaleuca alternifolia essential oil improved bactericidal activity when compared to the use of the oils without encapsulation (Souza, Baldissera, Santos, Raffin, & Baldisserotto, 2017).…”