Abstract
Background:
Catfish farming is often practiced with high stocking densities, which can result in environmental degradation, leading to stress and rendering the fish more vulnerable to infections such as Edwardsiellosis caused by E. tarda. Infection by E. tarda can occur through horizontal transmission during cohabitation of infected and healthy fish.

Aim:
This study aimed to investigate the hematological profile and the abundance of E. tarda in catfish following cohabitation with carrier silver rasbora.

Methods:
A total of 160 silver rasboras (length: 6.02±0.36 cm, weight: 2.065±0.565 g) were immersed in an E. tarda suspension at a concentration of 1013 CFU/ml for two weeks. Subsequently, they were cohabitated with 240 catfish (length: 6.9±2.35 cm, weight: 2.78±1.37 g) at different density ratios: 1:1 (P1), 1:2 (P2), 2:1 (P3), along with a negative control (without E. tarda, NC), and with E. tarda at 1013 CFU/ml (positive control/PC) for 5 days. The observed parameters included hematological profiles (total erythrocytes, leukocytes, hemoglobin levels, and leukocyte differentials) and the density of E. tarda in various catfish organs (liver, kidneys, and spleen).

Results:
The results indicated that catfish cohabiting with E. tarda-infected silver rasbora exhibited significant hematological alterations, including elevated percentages of neutrophils, lymphocytes, and monocytes, alongside decreased erythrocyte counts, hemoglobin levels, and total leukocyte counts. Furthermore, the highest density of E. tarda was detected in the liver (1.15±0.11 ×104 CFU/ml) in comparison to other organs.

Conclusion:
Cohabitation between healthy catfish and E. tarda-carrier silver rasbora resulted in bacterial infection in the catfish.

Key words: Catfish, Cohabitation, Edwardsiellosis, Fisheries, Silver Rasbora