Immune response of oreochromis niloticus against streptococcus iniae

Abstract EN

Skin darkening, gasping, exophthalmia, eye opacity, scale loss, hemmorrhage at the base of fins, fin rot, vertical position with the head down or up and protruded haemorrhagic vent were noticed on Oreochromis niloticus (Nile tilpia) experimentaly infected with Streptococcus iniae.

The mortality rate was 31.66 % in the infected.

Leucogram of O.

niloticus experimentally infected with streptococcus iniae revealed leucocytosis associated with heterophilia and lymphocytopenia at the 3rd day.

Leucocytopenia accompanied with heteropenia, lymphocytosis and monocytosis were noticed at the end of the 1st week till the end of the 4th week of experiment whlie heterophils and lymphocytes came back to normal at the last (5th) week of infection.

The total proteins were significantly increased at the 3rd day then significantly decreased at the 1st week of infection, till the end of the experiment at period.

The globulins were significantly increased at the 1st week of infection, till the end of the experiment.

AGPT demonstrated precipitating antibodies in serum samples of experimentally infected fish at the end of the 2nd week till the end of the experiment.

ELISA was more rapid and sensitive than AGPT and showed that the antibody titers agianst Streptococcus iniae increased significantly from the end of the 1st week, and reached its peak at the end of the 3rd week and stay there till the end of the experiment