PTGS2 and bacterial infectious disease: Modulation of cox-2 gene expression has been studied for parasite and bacterial infections in many fish species, showing upregulation in rainbow trout (Oncorhynchus mykiss) infected by myxozoans Myxobolus cerebralis and Tetracapsuloides bryosalmonae, monogenean Gyrodactylus derjavini, and in sea bream (Sparus aurata) infected by Photobacterium damselae subsp.