Health

Gill disease ther­a­pies

Fish Farmer - - Contents - BY CYRIL P. HENARD1, MATT LONGSHAW2, JAMES BRON1 & AN­DREW P. DESBOIS1

OF the pathogens im­pli­cated in caus­ing gill disease, it is amoebic gill disease (AGD) that presents the great­est prob­lems. The ae­ti­o­log­i­cal agent of AGD, Neop­ara

moeba pe­ru­rans, con­tains a sym­bi­otic part­ner, Perkin­sela sp., which lives in­side the amoeba and be­longs to a group of or­gan­isms called kine­to­plas­tids.

- ifor­nia in the late 1980s, but now this disease af­fects ev­ery ma­jor salmon pro­duc­ing coun­try.

The disease ex­erts a heavy eco­nomic bur­den through di­rect mor­tal­i­ties, a re­duc­tion in growth per­for­mance and the need for ex­pen­sive treat­ments, which presently are based mainly on hy­dro­gen per­ox­ide and fresh­wa­ter bathing.

Drug based ther­a­pies in aqua­cul­ture are con­ve­nient, par­tic­u­larly when ad­min­is­tered in feed, but few, if any, ef­fec­tive drugs are avail­able to treat AGD. In­deed, the to­tal num­ber of drugs avail­able in aqua­cul­ture is rel­a­tively lim­ited, es­pe­cially when com­pared to ter­res­trial farm­ing.

More­over, the drug ap­proval process is time con­sum­ing and ex­pen­sive, mean­ing any ap­proaches that min­imise these is­sues are at­trac­tive.

One pos­si­ble ap­proach is to re­pur­pose ex­ist­ing drugs that are al­ready ap­proved for use in aqua­cul­ture or have been used to treat sim­i­lar of Aqua­cul­ture.

‘First, we aimed to iden­tify all dis­eases caused by amoeba and kine­to­plas­tids in hu­mans and

‘In to­tal, 183 stud­ies were col­lected and con­tained in­for­ma­tion re­lat­ing to dis­eases sim­i­lar to AGD, no­tably 107 stud­ies re­lat­ing to disease caused by amoe­bae and 76 stud­ies of kine­to­plas­tids.

or are used as treat­ments for these re­lated dis­eases be­cause they may prove to be ef­fec­tive against Neop­aramoeba pe­ru­rans and/or Perkin­sela sp.

treat in­fec­tions caused by both amoeba and kine­to­plas­tid pathogens.

‘Next, we searched com­pound data­bases to iden­tify known drugs with sim­i­lar char­ac­ter­is­tics, and de­signed a scor­ing sys­tem to rank all the can­di­dates ac­cord­ing to the avail­abil­ity of in­for­ma­tion im­por­tant to gain­ing

The MPhil can­di­date, who joined the IoA in March 2018, con­tin­ued :‘ Fi­nally, we looked at Neop­aramoeba and Perkins el a genome sand metabol ranked can­di­date drugs are present in one or both of these or­gan­isms.

‘The next step of the project will be to eval­u­ate these can­di­date drugs for ac­tiv­ity against the AGD-caus­ing pathogens in vitro, be­fore ul­ti­mately

‘We hope that this project will lead to the in­tro­duc­tion of a new thera

Other ap­proaches be­ing pur­sued in Stir­ling to pre­vent AGD in­clude the devel­op­ment of a pro­tec­tive vac­cine; how­ever, un­til key gaps in the knowl­edge of the bi­ol­ogy and ecol­ogy of Neop­aramoeba pe­ru­rans are ad­dressed, this so­lu­tion re­mains a longer term goal.

In the mean­time, ef­forts con­tinue to re­pur­pose ex­ist­ing drugs as more ef­fec­tive and prac­ti­cal al­ter­na­tives for treat­ing AGD than hy­dro­gen per­ox­ide and fresh­wa­ter bathing.

For up­dates and more in­for­ma­tion on this project, con­tact: [email protected] and an­drew.des­[email protected] FF

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