Table 3 Histopathological scoring of H&E-stained sections categorized according to lesions degree of the gills, liver, spleen, and kidney of Nile tilapia exposed to PS-NPs and / or EO for 15 days

Gills lesions

Necrosis and vacuolation of the gill lamellae

-

+++

+++

+++

Sloughing and desquamation of lamellae

-

++

+++

+++

Shortening and curling of secondary lamellae

-

++

++

++

Fusion of secondary lamellae

-

++

++

++

Inflammatory cells infiltration

+

++

++

++

Expansion and congestion of central venous sinus

-

++

++

+++

Congestion of the lamellar blood vessels

-

+++

++

++

Liver lesions

Necrosis of the hepatocytes

-

++

+++

++

Hepatic cytoplasmic vacuolation

+

++

+++

++

Fatty infiltration of the hepatocytes

-

++

++

+++

Interstitial cells infiltration

-

++

++

++

Congestion and dilatation of the blood vessels

+

+++

+++

+++

Spleen lesions

Hemorrhage of red pulps

-

+++

++

+++

Lymphoid depletion of the white pulps

+

++

++

+++

Melanomacrophages infiltration

-

+++

++

+++

Protrusion of splenic trabeculae

-

++

++

++

Thickening of splenic capsules

-

++

++

+++

Congestion and dilatation of the blood vessels

-

++

++

++

Thickening of the blood vessels wall

+

+++

+++

++

Kidney lesions

Renal necrosis

-

+++

++

++

Degenerative changes of the renal tubules

+

++

++

+++

Inflammatory cells infiltration

+

+++

+++

+++

Hemorrhage of the hematopoietic tissues

+

+++

+++

+++

Melanomacrophages infiltration

-

+++

++

+++

Glomerular hypercellularity and congestion

+

++

+++

+++

Glomerular shrinkage and atrophy

-

++

++

++

Dilatation and congestion of the blood vessels

-

+++

++

+++