Literature survey of chemotherapeutic agents for re-purposing to treat amoebic gill disease caused by Neoparamoeba perurans

Abstract

Amoebic gill disease (AGD) is an important disease affecting marine fish including Atlantic salmon. The aetiological agent of AGD is Neoparamoeba perurans, an amoeba notably characterised by the presence of an intracellular kinetoplastid endosymbiont which belongs to the genus Perkinsela. This disease can cause high mortality and economic losses to salmon farming have been estimated at US$12.55 million in Norway in 2006 and US$81 million in Scotland in 2013. Current treatments include freshwater bathing and hydrogen peroxide but these methods are relatively impractical, effective against only mild cases, can stress the fish, and may represent 10-20% of present production costs. As a result, there exists an opportunity to develop a new chemotherapeutic intervention to treat AGD because such an approach could be beneficial with regard to cost-effectiveness, high treatment efficacy, improvement in fish welfare, and offering a long-lasting protective effect. This present study aimed to identify and prioritise existing drugs with efficacy against pathogens related to AGD that could be evaluated further as potential new chemotherapeutants for treating AGD. To this end, literature searching was performed to identify diseases of humans, animals and plants caused by amoebic and kinetoplastids parasites and the drugs used for treatment. In total, seven major relevant diseases were found to be caused by amoebae and kinetoplastid parasites, including amoebiasis and trypanosomiasis. A list of 118 drugs related to these diseases was established. From these 118 drugs, 222 drug targets were listed. Initially each drug was scored according to the amount of information available publicly that would be useful for seeking regulatory authorisation for use against AGD. Then, prioritisation was performed based on evidence for the presence of the target of the drug in AGD by use of iPath and BLAST software to investigate metabolic pathways and target proteins, respectively. This new bibliographic-based approach has highlighted numerous potential chemical candidates to assist in the development of new cost-effective and practical chemotherapeutic solutions for the Atlantic salmon farming industry to mitigate against AGD.