Impact of trypanosomiasis on the blood parameters and growth factor (K factor) on freshwater fish Heteropneustes fossilis (Bloch)

Like other living organisms, fishes could host internal or external parasites that, while may not be usually fatal, thrive at the host's expense, causing pathological and detrimental effects. Research on the pathological effects of Trypanosoma infections in fish remains limited, highlighting the need for further studies to understand their impact on fish health and physiology. This study investigates the pathological impact of Trypanosoma sp. infection on fish, focusing on inflammatory responses and physiological changes in blood parameters. Trypanosoma sp. infection was confirmed through blood smear analysis, which revealed significant alterations in hematological indices. Hemoglobin levels decreased markedly from 13.8% in uninfected fish to 9.50% in heavily infected fish. Erythrocyte counts also declined significantly from 1.80 × 10⁶/Cumm, while leucocyte counts increased from 21,400/Cumm to 26,400/Cumm as parasite load intensified. Mean corpuscular hemoglobin (MCH) values exhibited an initial rise during mild infections (60 Pg) but fell to 52.77 Pg during severe infections. Growth indices were notably impacted, dropping from 107.07% in uninfected fish to 77.73% in cases of heavy infection, correlating with increasing parasite density. These findings highlight the detrimental effects of Trypanosoma sp. on fish health, indicating reduced metabolism and suppressed growth in infected individuals. Blood diagnostics provide valuable insights into the physiological and pathological status of fish under parasitic stress, emphasizing the need for effective management strategies.