Disinfectant Effects of Formalin Solution on Experimental Infection of Clarias Gariepinus with Pseudomonas Aeruginosa

One of the challenges facing fish hatcheries is diseases killing fish hatchlings. Therefore, the disinfectant effects of formalin on experimental infection of Clarias gariepinus juvenile with Pseudomonas aeruginosa were investigated. The infection trial was carried out by immersion of fish in water containing isolates of P. aeruginosa at the rate of 5ml/L to achieve 4.5 x 108 CFU/L. Gills, liver, Intestinal mucosa, and skin of experimentally infected fishes were collected for bacterial re-isolation to ascertain Koch's postulate. The infected fishes were redistributed randomly in equal numbers per fish tank and then treated with 100, 150, 200, and 250ppm of formalin according to an exposure time of 5, 10, and 30 minutes for five days. The treatment of infected fish with 150ppm of formalin showed a significant difference. However, 200ppm of formalin with an exposure of 10 minutes to the experimentally infected fish showed a higher significant (p < 0.05) survival rate in comparison to other treatment doses and exposure time. The bacteria were multidrug–resistant and pathogenic and formalin (40%) was less toxic to C. gariepinus. Exerted disinfectant effects on infected fish with the bacterial isolates at 200pm for 10 minutes’ exposure time showed 90% survival rate. Keywords: Formalin, Pseudomonas aeruginosa, Disinfectant and Bacteria