break s ▁are ▁of ▁considerable ▁economic ▁importance ▁in ▁aqu ac ulture , ▁as ▁ep iz oot ics ▁can ▁result ▁in ▁moder ate ▁fish ▁loss ▁or ▁mass ▁mort ality ▁events ▁of ▁cult ured ▁fish es . ▁ ▁Tax onomy ▁ ▁The ▁family ▁I rid ov ir idae ▁is ▁divided ▁into ▁six ▁gener a ▁which ▁include ▁Ch lor ir id ov irus , ▁I rid ov irus , ▁L ym ph oc yst iv irus , ▁Meg al oc yt iv irus , ▁and ▁Ran av irus . ▁Meg al oc yt iv irus ▁isol ates ▁exhib it ▁relatively ▁few ▁gen etic ▁differences ▁and ▁have ▁been ▁divided ▁into ▁three ▁major ▁groups ▁based ▁on ▁gen etic ▁sequence ▁data ; ▁these ▁groups ▁are ▁represented ▁by ▁inf ect ious ▁s ple en ▁and ▁kid ney ▁ne c ros is ▁virus ▁( IS K N V ), ▁red ▁sea ▁b ream ▁ir id ov irus ▁( R SI V ), ▁and ▁tur bot ▁re dd ish ▁body ▁ir id ov irus ▁( TR B IV ). ▁ ▁R SI V ▁and ▁IS K N V ▁are ▁the ▁best ▁known ▁of ▁the ▁meg al oc yt iv ir uses . ▁ ▁Song , ▁et ▁al . ▁evaluated ▁ 4 8 ▁Asian ▁and ▁Australian ▁meg al oc yt iv irus ▁isol ates ▁with ▁regard ▁to ▁ge ographic ▁location ▁and ▁gen etic ▁variation ▁in ▁the ▁major ▁caps id ▁protein ▁gene ▁and ▁developed ▁a ▁ph y log en etic ▁tree ▁which ▁divided ▁the ▁ 4 8 ▁isol ates ▁into ▁three ▁distinct ▁clusters ▁based