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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. Key words: Aeromonas sobria; hematology; histopathology; Misgurnus mizolepis HEMATOLOŠKO-BIOKEMIČNE IN HISTOPATOLOŠKE SPREMEMBE PRI ČINKLJAH (Misgurnus mizolepis), EKSPERIMENTALNO OKUŽENIH Z Aeromonas sobria Povzetek: V raziskavi so bile preučevane hematološko-biokemične in histopatološke spremembe pri činkljah (Misgurnus mizolepis), okuženih z Aeromonas sobria. Ribe, okužene z 1×106 kolonij/ml A. sobria (25 rib x 3 ponovitve v 3 bazenih) in neokužene (kontrolne) ribe (25 rib x 3 ponovitve v 3 bazenih) so bile nastanjene v laboratorijskih akvarijih z ustreznimi parametri vode in bile evtanazirane 1., 3. in 5. dan po okužbi (PI). V petdnevnem poskusnem obdobju so okužene ribe postale letargične, škržne poklopce so hitro odpirale in zapirale, njihove škrge so postale blede in opazne so bile podkožne petehialne krvavitve. Hematološko-biokemični parametri, in sicer hematokrit, hemoglobin, celokupna količina beljakovin, celokupni kalcij, aktivnost alkalne fosfataze (ALP) in nivo glukoze so bili znatno zmanjšani, medtem ko so bili sečnina (UA), aspartat aminotransferaza (AST), alanin-aminotransferaza (ALT) in laktat dehidrogenaza (LDH) v okuženih ribah opazno povečani v primerjavi s kontrolno skupino rib. Skupno število levkocitov je bilo večje pri okuženih kot pri kontrolnih ribah po 3. dnevu PI, vendar se je 5. dan PI dramatično zmanjšalo. V beli krvni sliki so med obdobjem poskusa prevladovali limfociti in nevtrofilci. Histološka slika ledvic in vranice je pokazala obsežne krvavitve s celično nekrozo. V hepatocitih so bila vidna močno nekrotična žarišča s kariopiknozo, karioheksijo, kariolizo in hiperhromatozo jedrne membrane. Okužba z A. sobria je povzročila hematološko-biokemične spremembe, kot so anemija, hipoglikemija, hipoproteinemija, hipokalcemija, povečane aktivnosti AST, ALT in LDH, povečane koncentracije UA in zmanjšana aktivnost ALP, kar je privedlo do zmanjšane odpornosti na bolezen, poškodbe tkiva in nizke stopnje preživetja. Ključne besede: Aeromonas sobria; hematologija; histopatologija; Misgurnus mizolepis