2.8. Histopathological examination
Representative moribund tilapia (n = 3) from each challenge group and
apparently healthy tilapia (n = 3) from the control groups were examined
for histopathological changes. Tissues of affected fish (spleen, kidney,
liver, and brain) were collected and preserved in 10% buffered
formalin. After fixation for 24 h, sampled tissues were dehydrated in an
ethanol series, embedded in paraffin, and sectioned at 5 µm thickness.
The sections were then stained with hematoxylin and eosin, following the
standard histological protocol. Histopathological changes were examined
under a light microscope equipped with a digital camera (Olympus, Tokyo,
Japan).