In the present study, the causative agents of proliferative kidney disease (PKD) in both Oreochromis niloticus and Clarias gariepinus were identified based on the size and morphology of the spores and their polar capsules. The spores and polar capsules dimensions were measured by the Image J computer software. The occurrence of different myxosporean spores was confirmed by molecular biological technique using PCR with general and specific primers for different myxosporeans. Histopathological changes associated with PKD were recorded in both species. The results showed that there are 21 myxosporean species belonged to the genera Myxobolus, Chloromyxum, Myxidium, and Triangula. These include Myxobolus sarigi, Myxobolus amieti, Myxobolus distichodi, Triangula spp., Myxobolus heterosporous type2, Myxobolus brachysporous, Myxobolus tilapiae, Myxobolus heterosporous type1, Myxobolus equatorialis, Myxobolus exigus, Myxobolus hydrocuni, Myxobolus spp., Myxobolus dossoui, Myxobolus heterosporous1, Myxidium spp., Chloromyxum spp., Sphaerospora spp., Tetracapsuloid tilapiae, Thelohanellus spp., Henneguya spp., and PKDX tissue form. The PCR results showed bands at 1600 bp specific for Myxobolus spp., at 450 bp specific for Chloromyxum (tetracasuloid spp.), and at 1400 bp specific for spaherospora spp. in both Oreochromis niloticus and Clarias gariepinus. The general primer for myxozoan produced bands at 1700 bp whereas myxosprea specific but species unspecific primers produced bands at 900bp. Histopathological changes were evaluated by staining the fixed samples with H&E. Histopathological examination showed extrasporogenic stages of the parasite in the kidney interstitium surrounded by inflammatory cell infiltration. Necrobiosis of epithelial lining renal tubules was observed in many affected kidney tissues. Proliferation of interstitial fibrous connective tissue with vacuolization of the renal tubular epithelium occurs in some affected kidneys. |
