International Journal of Aquaculture, 2018, Vol.8, No.20, 151-155
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progression with extensive changes in the tissues of this vital organ. The inflammation of nephritic tubules of
challenged tilapia exemplified nephritis. The glomerulopathy and dilation of Bowman’s space are the indications
of a defective glomerular filtration of blood, which, in turn, hamper the removal of excess wastes and fluids from
the kidney. This clearly justified the ability of
A. caviae
in causing systemic infection as it contains many putative
virulence genes, including those encoding a type 2 secretion system, an RTX toxin, and polar flagella (Sudheesh
et al., 2012). The findings of this study are reasonably similar to those observed by Julinta et al. (2017) in
O.
niloticus
intramuscularly challenged with
A. hydrophila
, a strain isolated along with
A. caviae
strain used here. On
the other hand, in
A. hydrophila
challenged
O. mossambicus
, Azad et al. (2001) noted aggregation of
melanmacrophage centers (MMC) in the pronephros, necrosis of the cells in the renal interstitium, tubular
necrosis and glomerular degeneration, oedematous degeneration of the tubules, depletion of cells in the tubular
interstitium occlusion of the ophisthonephric collecting duct with MMC.
Figure 1 Photomicrography of the kidney tissues of
Oreochromis niloticus
intramuscularly infected with
Aeromonas caviae-
T
1
K
2
showing [a] normal architecture X400 H&E staining; [b] melanomacrophage aggregate (MA), glomerulopathy (G) with dilated
Bowman’s space (BS), nephropathy with the loss of tubular epithelial cells (LE), inflamed (I) and obliterated nephritic tubules (O),
widen lumen (W), necrosis (N) X200 H&E staining and [c] glomerulopathy (G), nephropathy with the loss of tubular epithelial cells
(LE), widen lumen (W), necrosis (N), inflamed nephritic tubules (I) and thickening of lumen lining (TL) X200 H&E staining
Figure 2 Photomicrography of the liver tissues of
Oreochromis niloticus
intramuscularly infected with
Aeromonas caviae-
T
1
K
2
showing [a] normal architecture X200 H&E staining; [b] dispersed (D) and necrotized (N) tissue, and fatty changes in the hepatic
parenchyma (F) X100 H&E staining and [c] melanomacrophage aggregate (MA), infiltration of haemocytes (IR) and loss of normal
architecture of the hepatic tissue X200 H&E staining
The liver of the control fish showed a normal structure and systematic arrangement of hepatocytes. The pancreatic
tissue inside the liver is not common in all kinds of fish, but if it is, this organ is called the hepatopancreas
(El-Bakary and El-Gammal, 2010). The observations of this study revealed the presence of pancreatic tissue inside
the liver of
O. niloticus
. In the liver and pancreas of challenged tilapia, dispersed and necrotized tissue, infiltration
of haemocytes, loss of normal architecture of the hepatic tissue, fatty changes in the hepatic parenchyma,
inflammation of pancreas as well as pancreatic acinar cells, and disintegration of intrahepatic exocrine pancreatic
tissues were commonly observed, which corroborate the observations of several earlier studies conducted on
different fish species due to
Aeromonas
infection (Azad et al., 2001; Ghosh and Homechaudhuri, 2012; Al-Yahya
et al., 2018). Azad et al. (2001) documented vacuolation, congestion of hepatic sinuses with blood cells and
internal haemorrhages, pyknotic necrosis of hepatocytes in the liver of
A. hydrophila
challenged
O. mossambicus
;
while in the pancreas, they observed acinar cell degradation in 3-5 dpi and mild necrosis in the pancreatic acini.
On the other hand, Al-Yahya et al. (2018) noted massive haemocyte aggregation, pyknotic nuclei in the
hepatopancreas and perivascular cuffing of hepatopancreatic haemolymph vessels in
A. hydrophila
infected blue
