Hemato-biochemical and histopathological changes in mud loach , Misgurnus mizolepis experimentally infected with Aeromonas sobria

Abstract

Hemato-biochemical and histopathological alterations in mud loach (Misgurnus mizolepis) infected with Aeromonas sobria were characterized in the present study. Fish infected with 1 × 106 colony forming units/mL of A. sobria (25 fish × 3 replicates × 3 tanks) and uninfected (control) fish (25 fish × 3 replicates × 3 tanks) were kept in laboratory tanks with adequate water parameters, and euthanized at 1, 3, and 5 days post-infection (PI). Infected fish became lethargic and developed rapid opercular movements, pale gills, and cutaneous petechial hemorrhages during the 5-day experimental period. Hemato-biochemical parameters, namely hematocrit, hemoglobin, total protein, total calcium, alkaline phosphatase (ALP) activity, and glucose level were significantly reduced, whereas urea (UA) level, and aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activities were markedly increased in infected fish compared to control fish. Total leukocyte count was higher of infected than in control fish by day 3 PI, but dramatically decreased on day 5 PI. The leukogram showed the predominance of lymphocytes and neutrophils during the experimental period. Histologically, kidney and spleen showed extensive hemorrhage with cellular necrosis. Liver cells showed severely necrotic foci with karyopyknosis, karyorrhexis, karyolysis, and hyperchromatosis of the nuclear membrane. Thus, A. sobria infection causes hemato-biochemical changes such as anemia, hypoglycemia, hypoproteinemia, hypocalcemia, increased AST, ALT, and LDH activities, increased UA concentrations, and reduced ALP activity, and lead to compromised disease resistance, tissue damage, and low survival rates.