PATHOGENICITY OF Pseudomonas aeruginosa IN RECIPROCAL HYBRIDS OF Clarias gariepinus AND Heterobranchus bidorsalis

Abstract

Farming of hybrids of two African Clariid catfish species, “Heteroclarias” is becoming a focus of attention in
many aquatic farms in Nigeria. Pseudomonas sp. is one of the major pathogens responsible for disease in
aquaculture. A total of 150 Heteroclarias juveniles were orally inoculated with different concentrations of
Pseudomonas aeruginosa ranging from 3 x 101
to 3 x104 CFU/100µl in 4 groups (A to D) replicated thrice, for
14 days with the aim of evaluating its pathogenicity. The control group (E) also with 10 fish in 3 replicates were
given normal saline orally. Clinical signs, mortality, histopathology and haematology were observed following
experimental infection. Haematological parameters observed were statistically analysed using SPSS 20. Clinical
signs observed in group A to C were discolouration, sloughing and patches of haemorrhage on their skin,
Frequency of mortality recorded in group A to E were 20%, 10%, 10%, 6.6% and 0% respectively.
Histopathological changes observed were vacuolar degeneration of renal tubular epithelium, diffuse
hepatocellular vacuolar degeneration, and hyperplasia, fusion of secondary lamellae, with haemorrhage in the
gills. Significant difference in haemoglobin concentration parameter was observed, translating to reduction in
oxygen carrying capacity of the infected fish. Heteroclarias were susceptible to Pseudomonas aeruginosa, with
resultant significant mortality.