An assessment of the use of drug and non-drug interventions in the treatment of Ichthyophthirius multifiliis Fouquet, 1876, a protozoan parasite of freshwater fish.

Infection by the ciliate protozoan Ichthyophthirius multifiliis Fouquet, 1876 causes significant economic losses in freshwater aquaculture worldwide. Following the ban on the use of malachite green for treating food fish, there has been extensive research aimed at identifying suitable replacements. In this paper we critically assess drug and non-drug interventions, which have been tested for use or have been employed against this parasite and evaluate possibilities for their application in farm systems. Current treatments include the administration of formaldehyde, sodium chloride (salt), copper sulphate and potassium permanganate. However, purportedly more environmentally friendly drugs such as humic acid, potassium ferrate (VI), bronopol and the peracetic acid-based products have recently been tested and represent promising alternatives. Further investigation, is required to optimize the treatments and to establish precise protocols in order to minimize the quantity of drug employed whilst ensuring the most efficacious performance. At the same time, there needs to be a greater emphasis placed on the non-drug aspects of management strategies, including the use of non-chemical interventions focusing on the removal of free-swimming stages and tomocysts of I. multifiliis from farm culture systems. Use of such strategies provides the hope of more environmentally friendly alternatives for the control of I. multifiliis infections.

In vitro treatments for the theront stage of the ciliate protozoan Cryptocaryon irritans.

The ciliate protozoan Cryptocaryon irritans Brown, 1951, the 'marine white spot', causes one of the most important parasitic fish diseases, with extensive losses every year in mariculture and in the ornamental fish industry. In the present study, we explore the in vitro use of 8 different compounds against the theront (infective) stage of C. irritans; these compounds include extracts of natural products (epigallocatechin gallate (EGCG), L-DOPA, papain), peracetic acid-based compounds (Proxitane 5:23 and 15% peracetic acid, PAA), quinine-based compounds (quinacrine hydrochloride and chloroquine diphosphate) and hydrogen peroxide. All of these compounds had an effect on theront survival; however, only EGCG caused significant theront mortality when applied in doses > or =50 mg l(-1) and over a period of 3 h; papain caused a maximum theront mortality of <50%. We discuss the type of application and potential utility of the compounds tested as part of a management control strategy for C. irritans infections in marine aquaculture and the ornamental fish industry.

Multi-centre testing and validation of current protocols for the identification of Gyrodactylus salaris (Monogenea).

Despite routine screening requirements for the notifiable fish pathogen Gyrodactylus salaris, no standard operating procedure exists for its rapid identification and discrimination from other species of Gyrodactylus. This study assessed screening and identification efficiencies under real-world conditions for the most commonly employed identification methodologies: visual, morphometric and molecular analyses. Obtained data were used to design a best-practice processing and decision-making protocol allowing rapid specimen throughput and maximal classification accuracy. True specimen identities were established using a consensus from all three identification methods, coupled with the use of host and location information. The most experienced salmonid gyrodactylid expert correctly identified 95.1% of G. salaris specimens. Statistical methods of classification identified 66.7% of the G. salaris, demonstrating the need for much wider training. Molecular techniques (internal transcribed spacer region-restriction fragment length polymorphism (ITS-RFLP)/cytochrome c oxidase I (COI) sequencing) conducted in the diagnostic laboratory most experienced in the analysis of gyrodactylid material, identified 100% of the true G. salaris specimens. Taking into account causes of potential specimen loss, the probabilities of a specimen being accurately identified were 95%, 87% and 92% for visual, morphometric and molecular techniques, respectively, and the probabilities of correctly identifying a specimen of G. salaris by each method were 81%, 58% and 92%. Inter-analyst agreement for 189 gyrodactylids assessed by all three methods using Fleiss' Kappa suggested substantial agreement in identification between the methods. During routine surveillance periods when low numbers of specimens are analysed, we recommend that specimens be analysed using the ITS-RFLP approach followed by sequencing of specimens with a "G. salaris-like" (i.e. G. salaris, Gyrodactylus thymalli) banding pattern. During periods of suspected outbreaks, where a high volume of specimens is expected, we recommended that specimens be identified using visual identification, as the fastest processing method, to select "G. salaris-like" specimens, which are subsequently identified by molecular-based techniques.