Evaluation of a point-of-care blood analyzer and determination of reference ranges for blood parameters in rockfish

OBJECTIVE: To compare values of blood parameters in rockfish obtained by use of a point-of-care portable blood analyzer with values determined by a veterinary diagnostic laboratory, calculate reference ranges for various blood parameters in black rockfish, and compare values of blood parameters in clinically normal fish with those of fish with clinical abnormalities. DESIGN: Prospective study. ANIMALS: 41 captive adult black rockfish (Sebastes melanops) and 4 captive adult blue rockfish (Sebastes mystinus). PROCEDURE: Rockfish were anesthetized with tricaine methanesulfonate for collection of blood samples. Heparinized blood samples were immediately analyzed with a point-of-care analyzer. Blood sodium, potassium, chloride, urea nitrogen, and glucose concentrations; Hct; pH; partial pressure of carbon dioxide; total carbon dioxide concentration; bicarbonate concentration; base excess; and hemoglobin concentration were determined. A microhematocrit technique was used to determine PCV, and a refractometer was used to estimate total plasma protein concentration. Paired heparinized blood samples were transported to a veterinary diagnostic laboratory for analyses. RESULTS: Data obtained with the point-of-care analyzer were reproducible; however, values for most blood parameters were significantly different from those obtained by the veterinary diagnostic laboratory. Fish with poor body condition had several blood parameter values that were lower than corresponding values in clinically normal fish. CONCLUSIONS AND CLINICAL RELEVANCE: Point-of-care blood analyses may prove useful in rockfish. Point-of-care data for a large number of clinically normal fish must be obtained for reference ranges to be calculated, and further assessments of clinically abnormal fish are necessary to determine the relevance of the data.     

Epitheliocystis disease in cultured pacu (Piaractus mesopotamicus) in Brazil.

Epitheliocystis disease was diagnosed in a cultured pacu (Piaractus mesopotamicus Holmberg, 1893) stock on the basis of gross pathological (greyish-white, pinpoint- or pinhead-sized focal areas, connected strongly to the gill lamellae) and histopathological examinations (hypertrophic cells 10-40 microns in size, having a well-defined wall and a central inclusion or characteristic granular content stained with Giemsa). The disease did not occur among fishes (Cyprinus carpio L., Ctenopharyngodon idella Cuv. and Val., Sarotherodon mosambicus Peters, Hoplias malabaricus Bloch) kept together with the affected pacus. About 30-40% of the pacu stock succumbed. Since branchial lesions and heavy mortality were observed in this pacu population, the aetiological role of the epitheliocystis agent could be suspected. Based upon ultrastructural examinations this agent is considered to be a chlamydia or a chlamydia-like organism.     

Two mortality events in sea-caged yellowtail kingfish Seriola lalandi Valenciennes, 1833 (Nannopercidae) from Western Australia

In November 2008 a commercial sea-cage operator farming yellowtail kingfish, Seriola lalandi, in Western Australia reported more than 70% mortality of the sea-caged fish. Several parasites and potentially pathogenic bacteria were isolated from the fish, but despite a detailed laboratory investigation the cause of the mortality event was never ascertained. That episode of deaths was followed in January 2009 by a smaller mortality event in fish in a sea cage that had been stocked several weeks earlier. Pathogens similar to those seen in the first mortality event were isolated, but again a single causative agent could not be identified. Multiple stress factors resulting in immunosuppression may have precipitated the mortality events.     

Transmission of Walleye Dermal Sarcoma and Lymphocystis via Waterborne Exposure

Abstract

A study was conducted to determine if walleye dermal sarcoma could be experimentally transmitted by waterborne exposure of tumor-free walleyes Stizostedion vitreum to tumor-positive walleyes by cohabitation. Uninfected walleyes were placed in a common raceway with tumor-positive fish for either 5 or 15 d. Direct contact between the two groups of fish was prevented by two screen barriers. The exposed fish were then maintained in the laboratory for a total of 20 weeks. Walleye dermal sarcoma developed in 89% and 71% of the fish exposed for 5 and 15 d, respectively. There was no significant difference (P > 0.05) in incidence of tumors between the two groups of fish exposed for different lengths of time.     

Massive mortality of common carp (Cyprinus carpio carpio) in the St. Lawrence River in 2001: diagnostic investigation and experimental induction of lymphocytic encephalitis

A massive fish kill affecting exclusively common carp (Cyprinus carpio carpio) in the St. Lawrence River, Québec, Canada, during the summer of 2001 was investigated by use of laboratory diagnostic methods and by an attempt to experimentally induce the disease. The ultimate causes of mortality were opportunistic bacterial infections with Aeromonas hydrophila and Flavobacterium sp. secondary to immunosuppression induced by physiologic (i.e., spawning) and environmental (i.e., high temperatures and low water levels) stressors, and possibly enhanced by an infection causing lymphocytic encephalitis observed in 9 of 18 (50%) fish examined. Experimental induction of disease was attempted in captured wild carp by administration of crude and filtered (particulate <0.22 microm) inocula prepared from a homogenate of tissues from carp affected by the natural outbreak. Although significant clinical disease or mortality was not induced by experimental challenge, lymphocytic encephalitis similar to the one observed in naturally affected carp was induced in four of seven (57%) fish administered crude inoculum and four of seven (57%) fish administered filtered inoculum. None of the control fish inoculated with sterile phosphate-buffered saline (n = 6) were affected by encephalitis. The cause of the encephalitis observed in carp from the natural outbreak and in experimentally inoculated fish could not be determined by use of virus isolation and transmission electron microscopy.     

An evaluation of the influence of stock origin and out-migration history on the disease susceptibility and survival of juvenile Chinook salmon

Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18-25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies.     

Journal of Aquatic Animal Health: Guide for Authors 2012

Abstract

A virus adsorption-elution (viradel) method for use with positively charged microporous filters was previously developed in our laboratory to concentrate waterborne infectious pancreatic necrosis virus (IPNV). In the present study, this method was evaluated for the detection of IPNV in water of laboratory aquaria containing IPNV-infected rainbow trout Onchorhynchus mykiss. Waterborne IPNV samples concentrated by the viradel method were compared with samples of sediment, fish tissue homogenate, and untreated water to determine how much the viradel method could improve rapidity and efficiency of virus detection. Results of three separate experiments indicated a significant, positive correlation between the virus titers in fish tissue and in the viradel method samples and between the sediment and untreated water samples.     

Experimental infection by Vibrio anguillarum in mice and guinea pigs.

The fish pathogen Vibrio anguillarum causes a lethal infection in farmed fish characterized by hemorrhagic septicemia. There are no reports of experimental laboratory infections in warm-blooded animals. We investigated the effects of an intraperitoneal infection with different doses of a V. anguillarum suspension in mice and guinea pigs. The infection caused a 95-100% of mortality in 24-48 h. Hemorrhagic septicemia was observed at necropsy and confirmed by histological and hematological examination. Immunohistochemically positive bacterial clumps were detected exclusively in vessel lumen in all examined organs, including brain, and V. anguillarum was reisolated in pure culture from all organs, particularly from the kidney. Blood analysis showed erythropenia and leukopenia with granulocytosis in mice, platelet reduction and leukopenia with lymphocytosis in guinea pigs.     

Susceptibility of Juvenile and Yearling Bull Trout to Myxobolus cerebralis and Effects of Sustained Parasite Challenges

Abstract

Evaluation of the susceptibility of bull trout Salvelinus confluentus fry to Myxobolus cerebralis infection using two different laboratory challenge models demonstrated that the method of administering the exposure dose affected infection prevalence. Administration of a low parasite dose (500 per fish) in a single exposure did not establish infection, but when the same cumulative dose was administered over 21 d the prevalence of infection was 45%. The results of challenges at a high exposure dose (5,000 per fish) were similar, infections being detected in 24% of the fish receiving a single dose and 40% of those administered the same dose in multiple exposures. Clinical disease was not detected in fish exposed via either challenge method. The susceptibility of yearling bull trout was tested by means of a single high dose of 10,000 per fish, and infection was detected in only 5% of those fish.     

Optimal Dosage of Erythromycin Thiocyanate in a New Feed Additive to Control Bacterial Kidney Disease

Abstract

An experimental feed additive containing erythromycin thiocyanate was formulated into fish feeds and tested to determine the optimal dosage and length of administration to treat acute infections of Renibacterium salmoninarum in chinook salmon Oncorhynchus tshawytscha. Trials were conducted on groups of yearling salmon acclimated and held in the laboratory at 10°C or 14°C in both the winter and spring. Parametric and nonparametric statistical analyses were used to assess survival rates during the tests and to evaluate the condition of fish alive at the completion of the trials. Survival was highest in trials of fish held at 10°C and among those fish that consumed higher quantities of erythromycin for 28 d of continuous therapy. Because portions of the daily rations were more likely to be refused when target dosages exceeded 100 mg/kg body weight, particularly in winter conditions, we recommend a standard therapeutic dosage of 100 mg/kg for 28 d.     

Determination of the median lethal dose of botulinum serotype E in channel catfish fingerlings

The median lethal dose of botulinum serotype E in 5.3-g channel catfish Ictalurus punctatus fingerlings was determined. Five tanks (five fish/tank) were assigned to each of the following treatment groups: 70, 50, 35, 25, or 15 pg of purified botulinum serotype E. Fish were injected intracoelomically and observed for 96 h. Administration of the toxin resulted in initial hyperactivity followed by erratic swimming, paresis, and death. The cumulative mortality by treatment group was 100% at 70 pg, 96% at 50 pg, 100% at 35 pg, 88% at 25 pg, and 56% at 15 pg. The median lethal dose was calculated as 13.7 pg/fish (equivalent to a 0.81 median lethal dose for mice Mus musculus) using a logistic regression model. All fish were necropsied; lesions included exophthalmia, ascites, splenic congestion, intussusception of the intestines, congested spleen, and blanching of the intestinal tract. The resultant clinical signs and lesions were similar to those noted in the syndrome of visceral toxicosis of catfish. This study indicates that channel catfish are more sensitive to the effects of botulinum serotype E than laboratory mice, and the signs and lesions of visceral toxicosis of catfish were replicated by injecting catfish with the toxin.     

An Evaluation of the Influence of Stock Origin and Out-migration History on the Disease Susceptibility and Survival of Juvenile Chinook Salmon

Abstract

Various methods have been developed to mitigate the adverse effects of the Federal Columbia River Power System on juvenile Pacific salmon out-migrating through the Columbia River basin. In this study, we found that hatchery-reared spring Chinook salmon Oncorhynchus tshawytscha in the river are in varying degrees of health, which may affect delayed mortality and the assessment of the effectiveness of management actions to recover listed stocks (e.g., barging fish downstream versus leaving fish in the river). A laboratory disease challenge with Listonella anguillarum was completed on fish from Rapid River Hatchery and Dworshak National Fish Hatchery (NFH) with different out-migration histories: (1) transported by barge, (2) removed from the river before barging, or (3) left to travel in-river. Barged fish from Rapid River Hatchery experienced less mortality than fish from Dworshak NFH. No statistical differences were found between the hatcheries with fish that had in-river out-migration histories. We suggest that the stressors and low survival associated with out-migration through the hydropower system eliminated any differences that could have been present. However, 18–25% of the fish that were barged or collected before barging died in the laboratory before the disease challenge, compared with less than 2% of those that traveled in-river. Owing to disproportionate prechallenge mortality, the disease-challenged populations may have been biased; thus, they were also considered together with the prechallenge mortalities. The synthesis of prechallenge and disease-challenged mortalities and health characteristics evaluated during out-migration indicated that the benefit of barging was not consistent between the hatcheries. This finding agrees with adult survival and delayed mortality estimates for the individual hatcheries determined from adult returns. The results suggest that the health status of fish and their history before entering the hydropower system (hatchery of origin and out-migration path) are critical variables affecting the conclusions drawn from studies that evaluate mitigation strategies.

Received November 18, 2009; accepted January 6, 2011     

Influence of light colours on growth and stress response of rainbow trout (Oncorhynchus mykiss) under laboratory conditions

Summary The influence of light colours on growth and stress response in rainbow trout Oncorhyncus mykiss (15.16 ± 0.29 cm; 32.27 ± 1.18 g) was studied. Fish were reared in 16 glass aquaria (140 × 30 × 80 cm) each with 12 fish under one of four different lighting spectra: yellow (546 nm), red (605 nm), blue (470 nm) and white (full spectrum, control). Experiments lasted 125 days. The stress response was evaluated by measuring cortisol levels. Body weight and total length of the fish reared under yellow light were greater compared with the other colour regimes while feed conversion ratio significantly lowers. Condition factor and specific growth rate, however, were not differentiated among experimental light treatments. Stressed fish showed lower cortisol levels under yellow light compared with other light exposures. The study indicates that under laboratory conditions, rainbow trout grow best under yellow light and that yellow light lowers the stress‐induced cortisol response in this fish species.     

Modulary effects of temperature on antibody response and specific resistance to challenge of channel catfish, Ictalurus punctatus, immunized against Edwardsiella ictaluri

The effects of various temperature treatments on the level of the humoral antibody response in channel catfish immunized with formalin killed Edwardsiella ictaluri was determined in laboratory controlled experiments. Immunized fish that were held at 25 degrees C for 30 days and 12 degrees C for an additional 30 days had higher antibody titers, and were more protected upon challenge, than immunized fish held at 25 degrees C for 60 days. Also immunized catfish held at 25 degrees C for 5 or 10 days followed by 12 degrees C water had higher antibody titers than immunized fish held at 12 degrees C or 25 degrees C for 60 days. In a field experiment carried out during winter and spring (February-May) fingerling channel catfish were vaccinated with E. ictaluri using intraperitoneal injection or immersion with either sonicated or whole cell preparations. Following challenge, the fish vaccinated by immersion in the sonicated preparation had 11.8% mortality whereas the groups immersed in whole cell bacterin, injected with the whole cell bacterin in adjuvant, or injected with sonicate showed 24.6, 57.9 and 41.7% mortality, respectively. Although the fish vaccinated by immersion with the sonicated bacteria had lower antibody titers than those vaccinated by the other methods the immersion vaccinates were more protected against challenge with the pathogen.     

The effect of diets supplemented with fish broth and fish oil on the health of weaners

The aim of this study was to determine the effect of fish-based feed materials, as a source of readily available protein contained in fish broth and essential polyunsaturated fatty acids (PUFAs) found in fish oil, on the health of piglets and rearing results. The experiment was conducted on a commercial pig fattening farm. The study involved a total of 80 weaners with an approximate body weight of 15 kg. The experiment was carried out over a period of 40 days. Feed samples were subjected to laboratory analyses. Blood samples were collected from experimental group animals to determine serum biochemical and immunological parameters. The body weight gains of weaners, mortality rates and average feed intake per animal were calculated for the entire experimental period. The addition of fish broth and fish oil significantly improved the n3:n6 fatty acid ratio in diets. The presence of EPA and DHA in the experimental diet could have had a positive health effect on piglets, comparable with that exerted by therapeutic doses of zinc often administered to pigs of this age group. During the experiment, feed conversion ratio (FCR) gain was considerably reduced in the experimental group, with similar daily gains in the control and experimental group.     

17株水产动物病原菌的表型及分子遗传学鉴定

1996-1999年从患病鱼、鳖、蟹等水产动物体内分离并保存了17株病原菌．采用ATB expression细菌鉴定系统对这l7株病原菌进行表型鉴定．并应用优化的热变性温度法（Tm法）分别测定其染色体DNAG＋C mol％含量，进行分子遗传学鉴定，从而确定了17株病原菌的种属。     

Ectopic Hermaphroditic Gonad in the Cranial Cavity of Japanese Medaka

Abstract

Diseases were monitored for 1 year in a cohort of approximately 560 Japanese medakas Oryzias latipes kept in a laboratory at Tulane University. The fish were maintained as part of a breeding colony for embryological studies. Eighty-six fish exhibiting disease or injury during the year were examined histopathologically. Two adult Japanese medakas (one male and one female) had ectopic hermaphroditic gonads in the cranial cavity. The ectopic gonads were bordered by meninges and cranium. The ectopic gonads in both cases consisted mostly of spermatocytes and spermatids with numerous islands of primary germ cells and a few ovarian follicles. An ectopic gonad in the cranial cavity has not been previously reported in vertebrates.     

Behavioral type,in interaction with body size,affects the recapture rate of brown trout Salmo trutta juveniles in their nursery stream

Movement activity levels of wild animals often differ consistently among individuals, reflecting different behavioral types. Previous studies have shown that laboratory‐scored activity can predict several ecologically relevant characteristics. In an experiment on wild brown trout Salmo trutta, spanning from June to October, we investigated how spring swimming activity, measured in a standardized laboratory test, related to relative recapture probability in autumn. Based on laboratory activity scores, individuals clustered into 2 groups, which showed contrasting patterns in the size‐dependency of their recapture probability. Size had a slightly positive effect on recapture probability for passive fish but a clear negative effect on active fish. Our results show that the population structure in a cohort, in terms of relative proportions of behavioral types in different size classes, can vary over time. The results of this study could depend on either selective mortality or migration. However, selective disappearance of individuals with specific phenotypes, regardless of the mechanism, will have implications for trout population management, such as stocking efficiency of hatchery fish with high growth rates or maintenance of fishways past migration barriers.     

Tilapia (Oreochromis niloticus) dosed with azathioprine display immune effects similar to those seen in mammals, including apoptosis.

Azathioprine, an anti-neoplastic drug and therapeutic immunosuppressant, was administered intraperitoneally at 10.0 and 50.0 mg/kg to 3-6-month-old tilapia (Oreochromis niloticus). Consistent alterations in immune cellular parameters of the blood, pronephros (hematopoietic kidney) and spleen were observed. Peripheral blood total cellularity decreased as the azathioprine dose increased, to approximately half that of the control. Differential analysis of white blood cells indicated a decline in lymphocyte number, in particular, with increased dosage of azathioprine. Pronephric total cellularity was depressed in fish receiving the 10.0 or 50.0 mg/kg dose. In contrast, both splenic weight and splenic total cellularity increased proportionately with the increase in the drug dosage. Histopathologic examination of the spleens showed normal patterns for both control and 10.0 mg/kg dose groups. At 50.0 mg/kg, spleens were characterized by marked expansion of the white pulp, although lymphocytes were rare. Melanomacrophage centers at the higher dose were also larger and more numerous than in the control group. Evaluation of splenic and pronephric leukocytes with apoptotic markers showed an increase in apoptotic cells in the pronephros with increasing drug dose. These changes in fish are consistent with those seen in humans and laboratory rodents dosed with azathioprine, suggesting that fish may be potentially useful as preliminary models for detecting immunosuppressive compounds.     

Eutrophication,Ammonia Intoxication,and Infectious Diseases: Interdisciplinary Factors of Mass Mortalities in Cultured Nile Tilapia

The present study was designed to assess the possible causes of the mass mortalities of Nile Tilapia Oreochromis niloticus at El-Behera Governorate, Egypt, in relationship to environmental and microbiotic factors. Water samples were collected from fish farms at different locations and from Lake Edku to analyze water temperature, water pH, salinity, biological oxygen demand, dissolved oxygen, total ammonia nitrogen, and un-ionized ammonia. A number of moribund and freshly dead fish were sampled and submitted to our laboratory for microbiological, molecular, and histopathological examination. Water analysis of the fish farms revealed noticeable increases in the previously mentioned physicochemical parameters. Clinical examinations of moribund fish showed severe gill rot and massive external and internal hemorrhages. Ordinary and molecular laboratory findings confirmed the presence of Branchiomyces sp. in gill tissue and mixed bacterial fish pathogens (Streptococcus agalactiae, Vibrio alginolyticus, V. parahaemolyticus, Pseudomonas anguilliseptica, and P. aeruginosa) in visceral organs. The histopathological and transmission electron microscopic examinations revealed severe necrosis of gill filaments and blockage of branchial blood vessels and lamellar capillaries with Branchiomyces sp. hyphae and spores mixed with different shapes of bacteria. Severe inflammations were detected in liver, kidney, heart, and brain tissues. Ultimately, we can conclude that the syndrome of mass fish kills in this area is a consequence of ecological damage to the aquatic environment, which is mainly related to natural and anthropogenic factors, as well as to the presence of infectious agents.

Received September 30, 2015; accepted April 12, 2016 Published online August 2, 2016