Cajeput oil, an effective botanical against gyrodactylid infection

Abstract

Infectious diseases are a major welfare issue, economically costly and, from a conservation perspective, threaten susceptible fish populations. Parasite control in aquaculture is over reliant on a limited range of treatments which tend to be low in efficacy, toxic to hosts and have negative consequences on human health and the environment. Here, we tested 22 botanical treatments alongside five controls against Gyrodactylus turnbulli (Harris 1986), in vitro and in vivo, infecting guppies (Poecilia reticulata Peters 1859). Survival of detached parasites was significantly reduced by all treatments with cajuput oil, bay rum oil, bladderwrack, octanoic acid, pine tree oil and barberry killing worms instantly. In vivo, cajuput oil applied with emulsifier was as effective as a licensed livestock dewormer, Levamisole, which is not routinely prescribed for use in fish; hence, cajuput can be considered for further research to replace Levamisole in UK research laboratories as well as in ornamental aquaculture.

Aquatic Parasite Cultures and Their Applications

“…The continued pursuit to optimise aquatic parasite culture techniques will enable researchers In vitro and in vivo monogenean cultures have been used to examine the efficacy of commercial [91] and natural products [17,92,93] as well as biocontrols [94]. In vivo culture enabled parasite life cycle parameters to be examined in response to varied environmental parameters which were used to develop strategic treatment regimens on aquaculture farms [10,74].…”

Efficacy of commercially available products against Gyrodactylus turnbulli infections on guppies Poecilia reticulata

“…Indeed, cajuput applied with Tween 20 was nearly as effective as the Melafix ® /Pimafix ® combination with approximately 90% ef ficacy using G. turnbulli infecting gup pies (Poecilia reticulata) (see Schelkle et al 2015). The longer dur ation of exposure and a lower dose of the cajuput treatment in the current study increased the efficacy to 95%.…”

“…By preparing the mixture in the laboratory, the compounds may have been affected by light degradation or oxidation processes which, in turn, may have affected treatment efficacy. Finally, seeing that cajuput has previously been shown to be highly anti-parasitic (Schelkle et al 2015), a double dose of Melafix ® by itself may be equally as effective as the combination treatment used in the current study; however, such speculation would have to be confirmed through further testing.…”

“…Water and the anti-helminthic levamisole (Levacide) were used as negative and positive controls. Both Melafix ® and Pimafix ® were tested at the concentrations recommended by the manufacturer (see Table 1), the individual and combination treatments were administered to reflect the concentration in the products and levamisole was used at the known effective concentration of 1 ml l −1 (Schelkle et al 2009(Schelkle et al , 2015.…”

“…Research on related botanical extracts or various host−parasite combinations indicates that particularly emulsified cajuput oil may be effective against parasitic worms (Steverding et al 2005, Yousif et al 2007, Schelkle et al 2015; however, neither Melafix ® nor Pimafix ® have been tested against helminths in an aquatic environment. In this study the efficacy of Melafix ® and Pimafix ® and their individual essential oil components was tested in vitro and in vivo against gyrodactylids.…”