Non specific immune response in the African catfish, Heterobranchus longifilis fed diets fortified with ethanolic extracts of selected traditional medicinal plants and disease resistance against Pseudomonas aeruginosa
The efficacy of supplementing diets with ethanolic extracts from three medicinal plants (Arabic gum; Acacia arabica, Water lily; Nymphaea lotus, Iron weed; Vernonia ambigua) on the innate immune response and diseases resistance in Heterobranchus longifilis challenged with Pseudomonas aeruginosa were studied. H. longifilis juvenilles (20.4 ±3.8g) were fed diets containing 0% (control diet C), 1.5% extracts of; Acacia Arabica (diet 1), Nymphea lotus(diet2) and Vernonia ambigua (diet 3) 100g-1 of feed at 5% biomass daily and the innate immune response parameters were examined after the end of the experimental period (42days). The blood leukocyte phagocytic activity was enhanced in fishes fed diet 2 and diet 3 from the 14th day while those fed diet 1 showed no significant(P>0.05) increase until the 28th day. Serum lysozyme activities were stimulated in fish fed diet 2 from the 14th day while significant increase were recorded from the 28th day in those fed diet 1 and diet 3. Significantly (P<0.05) increased leukocytes respiratory burst activity were only observed from the 42nd day in all the experimental diets but there was no significant change (P>0.05) in any of these parameters in the control group. A challenge test with virulent strain of Pseudomonas aeruginosa following 42days of feeding showed 100% mortality in the bacterial infected H. longifilis in the control group by the 15th day, while mortalities recorded for the fishes fed the diet supplemented groups; diet 1, diet 2 and diet 3 were 52% (relative percent survival (RPS) 48%), 44% (RPS=56%) and 68% (RPS=32%) respectively at the end of the challenge experiment (24days). The cumulative mortality index for the control group was 130.8 which was equated to 1%, while the lowest mortality of 0.26% was obtained in the D3 diet fed group and were significantly different (P<0.05) in all the treatment groups. These results suggests that the dietary inclusion of these plants extracts may elevate the innate immune response and enhanced disease resistance in H. longifilis.
Keywords: Heterobranchus longifilis, innate immune response, plant extract, Pseudomonas aeruginosa.