THE PATHOLOGICAL AND HAEMATOLOGICAL EFFECTS OF Aeromonas hydrophila ON WALKING CATFISH (Clarias gariepinus)

Abstract

A comparative study was carried out to determine the effects of saline suspensions of either unwashed, washed or sonicated washed cells of a virulent strain of Aeromonas hydrophila on walking catfish, Clarias gariepinus. Three doses of 106, 107, and 108 cfu/ml were prepared from each of the above bacterial suspensions and injected Intramuscularly into healthy catfish fingerlings. With the injection of 106 cfu/ml, both washed and sonicated washed cells caused a mild inflammation at the injected site which returned to normal after 48 hrs. Mortality was 60%, which occurred only from 3 to 12 hrs. In contrast, injection of the unwashed cells induced a stronger reaction than that of the washed and sonicated washed cells. Mortality was also 60% but occurred from 12 to 24 hrs. With an injected dose of 10⁸ cfu/ml, both washed and sonicated cells induced more marked inflammation with haemorrhage at the injected site. Mortality (60% for W-Injected and 90% for So- injected) occurred only from 3 to 12 hrs. The injured tissues of the survival took 120 hrs for recovery. On the other hand, an injection of 10⁸ cfu/ml unwashed cells would kill all the fish at 48 hrs and their blood was completely hemolysed. The variations in haematocrit value and blood differential counts after the injection of the different types and dilutions of bacterial preparations were discussed.