Physiological and Hematological Changes in Chum Salmon Artificially Infected with Erythrocytic Necrosis Virus

Abstract

Chum salmon Oncorhynchus keta were injected with erythrocytic necrosis virus (ENV) to study the physiological and hematological consequences of ENV infection. Infected and control fish were held in pathogen-free seawater and sampled for 5 weeks. Physiological tests included measures of plasma cortisol, glucose, protein, and osmolality; blood lactic acid; and liver glycogen. In general, ENV-infected fish had lower plasma glucose and blood lactic acid, and higher liver glycogen concentrations than did control fish. Hematological tests included red and white blood cell (RBC and WBC) counts, hematocrit, measurement of blood hemoglobin concentration, and a determination of erythrocyte fragility. Infected fish had lower RBC counts, hematocrits, and hemoglobin concentrations; higher WBC counts; and less fragile erythrocytes than did control fish. The hematology data indicated that erythrocytes of infected fish had higher mean corpuscular volume, depressed mean corpuscular hemoglobin concentration, and slightly lower mean corpuscular hemoglobin. Erythrocytic inclusions were observed in the cytoplasm of RBCs from infected fish. The infection progressed steadily through week 4, after which the fish appeared to begin recovering. In a second study, fish were infected with ENV for 3 weeks, and recovery from a stress challenge test was measured. Plasma glucose concentrations and osmolality were higher in infected fish, whereas plasma cortisol and blood lactate were only slightly elevated. These studies indicate that chum salmon withstood the effects of ENV infection without irreversible physiological consequences. However, when subjected to a stress challenge test, infected fish recovered more slowly than control fish and had increased osmoregulatory difficulties.

Haematological changes in Nile tilapia experimentally infected with Enterococcus sp.

“…On the other hand, fish injected with 1 x 10 6 CFU/mL of Enterococcus showed increased WBC, hematocrit and total number of thrombocytes. Haney et al (1992) and Pathiratne and Rajapakshe (1998) have reported increased WBC corroborating our data. Total leucocyte counts suggested severe leucocytosis of 15.0 x 10 3 WBC/ l in control to 27.3 x 10 3 WBC/µl in fish injected with 1 x 10 6 CFU/mL of Enterococcus.…”

“…For example, decreased red blood cells and hematocrit were found in coho salmon (Oncorhynchus kisutch) infected with V. anguillarum (Harbell et al, 1979); in Asian cichlid fish (Etroplus suratensis) with epizootic ulcerative syndrome (Pathiratne and Rajapakshe, 1998); in rainbow trout (Oncorhynchus mykiss) with ulcerous dermatitis (Rehulka, 1998); in rainbow trout experimentally infected with Aeromonas sobria and A. caviae (Rehulka, 2002); in carp (Cyprinus carpio) experimentally infected with A. hydrophila (Harikrishnan et al, 2003) and in Nile tilapia experimentally infected with Streptococcus iniae (Chen et al, 2004). On the other hand, an increase in the white blood cells and glucose was observed by Haney et al (1992) in chum salmon (Oncorhynchus keta) with erythrocytic necrosis virus.…”

Potential use of probiotic- and triherbal extract-enriched diets to control Aeromonas hydrophila infection in carp

“…Monitoring these values and profiling leucocytes provides information about the general immune status of the fish. In our study, RBC levels, Hb and Ht declined significantly in the infected, untreated group, indicating the destruction of RBCs leading to anaemia (Haney et al 1992, Denton & Yousef 1975. Such reductions have been confirmed in yellowtail flounder Limanda ferruginea (Allen et al 2003) infected with various pathogens.…”

“…Similar trends have been reported in Atlantic salmon infected with Vibrio (Waagbo et al 1988), and in rainbow trout infected with haematopoietic necrosis virus (Amend & Smith 1975). Haney et al (1992) found that the total plasma protein and glucose levels increased in fish fed with probiotics-enriched diets due to the destruction of RBCs and the resultant release of cell contents into the blood stream.…”

Hematological characteristics associated with parasitism in Pikeperch Sander lucioperca (Percidae) from Anzali Wetland

“…Hemoglobin content was measured with a spectrophotometer at 540 nm absorbance using the cyanmethemoglobin procedure. The haematological indices including mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) were calculated according to Haney et al (1992). Mann-Whitney (U) test was used for normality of data distribution and homogeneity of variance, as well as Kruskal-Wallis (K) analysis were applied to the data for determine the existence of any meaningful difference in mean intensity of the parasite species.…”