Ichthyphthirius multifilis infection induces apoptosis in different species of tilapia

الملخص EN

The parasitic ciliate Ichthyophthirius multifiliis (Ich) is one of the most im¬portant protozoan pathogens of freshwater fish worldwide.

Examination of 4 species of Tilapia from the River Nile recorded highest rate infection in Oreochromis niloticus, followed by Oreochromis aureus, Sarotherodon gali-laeus and Tilapia zilli.

By electron microscopy, apoptotic cells collected from Tilapia species infected with "Ich" showed an aggregation on the apical and basal parts of the ciliated and non-ciliated endothelial lining the gill epithelium.

Ultrastructural analysis showed that the chromatin in the liver of Ich-infected 0.

Niloticus was highly condensed and massed at the center of the nucleus.

Ul¬trastructural analysis of "Ich" infected O.

aureus showed that the nuclear mem¬brane of hepatocytes was also shrunken.

In S.

galilaeus, chromatin was highly condensed, fragmented and massed at the nuclear center, occasionally forming crescent-shaped masses.

Ultrastructural of 0.

Niloticus spleen showed that the macrophage number was comparatively high as compared to control.

In O.

au¬reus, damaged splenic cell number did not change, and phagocytic capacity of macrophages was not very high.

In Ich-infected S.

galilaeus, a marked decrease in splenic cells number was seen.

Analysis of DNA by agarose gel electropho¬resis on gill, liver and spleen cells showed a ladder of DNA fragments in mul¬tiple of 180bp in length, pointing to an internucleosomal DNA cleavage