No abstract

No abstract

Fishes are the most successful and diverse group of vertebrate animals, first appeared during Devonian period. Despite of certain differences, the immune system of fish is physiologically similar to that of higher vertebrates. The heterogenous group of fishes are the apparent link between innate immunity and the first appearance of the adaptive immune response. Importantly, fishes have immune organs homologous to that of mammalian immune system. In comparison to higher vertebrates, fishes live free in their environment from the early embryonic stage and during that time mostly they are dependent on non-specific immune system for their survival. In the fishes, non-specific immunity is the fundamental defense mechanism, therewith acquired immunity also plays key role in maintaining homeostasis by activation though a system of receptors proteins, which identify pathogen associated molecular pattern typical of pathogenic microorganism includes lipopolysaccharides, peptidoglycans, DNA, RNA and other molecules that are typically not present on the surface of multicellular organism. There are several external factors like environmental factors, biological factors, stress and internal factors like genetic makeup, age and sex, maternal effect etc. can affect immunological defense capabilities of the fishes.

Cage farming of Pangas catfish (Pangasionodon hypophthalmus) in small reservoirs is primarily profitable. Still, sustainability in terms of disease and environmental impact issues remains unsolved. In the present study, Pangas catfish from selected farms were screened for bacteria and parasites from 2017-18. In the present study, several Gram-negative bacterial species, including Edwardsiella tarda, Aeromonas hydrophila, A. veronii, Pseudomonas putida, Enterobacter cloacae, and Plesiomonas shigelloides, were isolated. A high prevalence of Aeromonas and Pseudomonas infections was noticed in cage farms. The most prevalent isolate was A. veronii (9 isolates), followed by P. aeruginosa and P. putida, revealing the presence of biotic stress.Furthermore, potential human pathogenic bacteria, particularly Klebsiella pneumoniae, P. aeruginosa, Acinetobacter baumannii, Citrobacter freundii, and Morganella morganii, were isolated. Histopathological analysis of the vital organs concluded the extent of damage caused due to the biotic stress in the cage culture system. The antibiotic sensitivity test implied resistance of bacteria for Sulphamethoxazole and Tetracycline. Some of them were resistant to multiple drugs, the risk for public health. Water temperature, dissolved oxygen, pH, Aeromonas, Pseudomonas, and Plesiomonas were identified by principal component analysis as significant abiotic and biotic stress factors. This information helps design predictive disease models.