Experimental Challenge Models and In Vitro Models to Investigate Efficacy of Treatments and Vaccines against Amoebic Gill Disease.

Jemma Hudson,Barbara F Nowak

doi:10.3390/microorganisms9040710

Abstract

Amoebic Gill Disease (AGD) severely affects salmonid mariculture due to fish losses and costs associated with management of the disease. Continued research into management solutions, including new treatments and vaccine development, is highly important for the future of salmonid production worldwide. This requires both in vitro (both pathogen only and host-pathogen models) and in vivo (disease challenge) testing. Challenge models are still widely varied, in particular with regard to: infection methods (cohabitation or immersion), source of the pathogen (isolated from infected fish or cultured), infectious dose, environmental conditions (in particular temperature) and the endpoints across experimental treatment and vaccine studies which makes comparisons between studies difficult. This review summarises in vitro assays, the challenge methods and endpoints used in studies of experimental treatments and vaccines for AGD.

Highlights

Amoebic Gill Disease (AGD) is a potentially fatal disease that primarily affects salmonids farmed in marine environment, it has been reported from other farmed marine species [1,2,3,4,5]
Either vaccines or treatments, are generally developed for aquaculture industries, it follows that the challenge models used to develop these vaccines and treatments should be as close as possible to the natural transmission methods so they are the most relevant to industries
Due to the nature of AGD differing in its epidemiology globally, it would be reasonable for experimental studies to develop management solutions that apply to local aquaculture industries

Summary

Introduction

Amoebic Gill Disease (AGD) is a potentially fatal disease that primarily affects salmonids farmed in marine environment, it has been reported from other farmed marine species [1,2,3,4,5]. Specific guidelines have been developed for vaccine trials in fish, to ensure clinically relevant data are collected without unnecessary harm to subject animals These guidelines, created in 1981 [31], require that a minimum of 25 fish per replicate are used, with control and treatment groups being at least duplicated. The success of treatments or vaccines can be measured through the survival/mortality of fish over the length of a study, severity of gill lesions, or amoebae load on the gills. This review discusses both in vitro and in vivo testing methods, including challenge methods and the endpoints for vaccine and treatment testing used in studies of AGD

In Vitro Testing

In Vivo Challenge Methods

Aim

Endpoints of In Vivo Challenge Studies

Findings

Conclusions