Browsing by Author "Smith, Stephen A."
Now showing 1 - 20 of 57
Results Per Page
Sort Options
- Acute toxicity of ammonia and nitrite to Pacific White Shrimp (Litopenaeus vannamei) at low salinitiesSchuler, Dominic (Virginia Tech, 2008-04-30)The Pacific white leg shrimp, Litopenaeus vannamei, is a potential species for low salinity inland aquaculture. Due to several independent variables, such as species, age, size, salinity and pH, that must be taken into account, there are gaps in the literature pertaining to the toxicity of ammonia and nitrite to shrimp. This study was conducted to investigate the individual and combined effects of ammonia and nitrite on L. vannamei postlarvae (25-45 days old) at 10 ppt salinity, 28 C and a pH of 7.8. The independent variables were salinity, total ammonia as nitrogen (TAN) and nitrite-N (NO₂-N), separately and combined. The TAN experiments were conducted at 18 and 10 ppt salinity while the NO₂-N test was conducted at 10 ppt salinity. Combined TAN and NO2 tests were also conducted at 10 ppt salinity. The LC50 values for TAN at 18 ppt salinity, TAN at 10 ppt salinity, and NO2-N at 10 ppt were observed to be 42.92, 39.72 mg/L (2.26 and 2.09 mg/L unionized ammonia-N), and 153.75 mg/L, respectively. When NO₂- N was adjusted to the LOEC level and TAN concentrations were varied, synergistic effects were observed, with an LC50 calculated to be 28.2 mg/L TAN (1.49 mg/L unionized ammonia-N). However, when the ammonia level was adjusted to the LOEC and nitrite was varied, antagonistic effects were observed with an LC50 calculated to be 163.3 mg/L NO₂-N. The results suggest that further investigations into the combined effects of ammonia and nitrite at varying concentrations and lower salinities will be important in developing "standard operating procedures" for the shrimp industry.
- Aquaculture of Pacu (Piaractus mesopotamicus) and a Comparison of its Quality: Microbiological, Sensory, and Proximate CompositionPullela, Sharma V. S. (Virginia Tech, 1998-08-21)(Piaractus mesopotamicus) initially weighing 72.0 g were fed three diets - a) 0.5% vegetable (zucchini), b) commercial 32% (P32) and c) commercial 36% (P36) protein diets for 24 weeks and their growth performance compared. Processing yields and proximate composition were determined following dressing of pacu. The microbiological quality of pond cultured pacu was compared to aquacultured hybrid striped bass, tilapia, and rainbow trout grown in pond and recirculating aquaculture systems. Sensorial analyses for differences in flavor, preference, and color were also determined. Protein concentration significantly influenced the weights, lengths, specific growth rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Diet insignificantly influenced the processing yields (p > 0.05). The moisture, protein and total lipid contents were significantly affected (p < 0.05) by the dietary protein. The indicative bacterial quality differed significantly for pacu as well as the water used for culturing pacu (p < 0.05) among dietary treatments. Aquaculture production systems significantly influenced the indicative and pathogenic bacterial quality. Listeria monocytogenes, Salmonella spp., Yersinia enterocolitica, and Escherichia coli O157:H7 were not isolated from any of the sampled fish. The qualitative and quantitative results of Clostridium botulinum were influenced by the production system (p < 0.05). Flavor of pacu was comparable to that of hybrid striped bass, tilapia, and rainbow trout, but superior to catfish. Cooking significantly improved the color of the ground fish fillets.
- Bacterial Kidney Disease and Its effect on the Salmonid Immune responseDensmore, Christine L. (Virginia Tech, 1997-11-04)Renibacterium salmoninarum, the etiological agent of bacterial kidney disease (BKD) of salmonid fish, is a pathogen of great concern among fisheries and the aquaculture industry worldwide. Previous investigations have indicated the pathogenesis of BKD is complex. It is a chronic, multisystemic, granulomatous disease with a number of potential immunomodulatory effects on the host. Given the current limitations for treatment and control of BKD, it is imperative that the pursuit of development of methods of prevention, namely management strategies and vaccination, be continued. To do so, the immunology of BKD must be elucidated in order to better understand and manipulate the associated immune responses to our advantage. This dissertation is composed of four chapters which relate to BKD and the associated immune responses of three species of susceptible salmonid fish as follows: Exogenous stress factors, through stress-induced immunosuppression, have been shown to influence BKD development in cultured salmonids. Chapter 1 examines the effects of two environmental stressors common to fish culture, overcrowding and overfeeding, as they affect BKD development and R. salmoninarumantigen prevalence among juvenile chinook salmon (Oncorhynchus tshawytscha) Immunomodulatory interaction between pathogen and host in BKD is widely reported and merits further investigation. Particularly, the immunological parameters affected and the role of the extracellular protein (ECP) of R. salmoninarum are of interest. Chapter 2 examines the in vivo immune response of rainbow trout (Oncorhynchus mykiss) following exposure to the ECP in terms of both humoral and cell-mediated immunological parameters, including the immune response against another bacterial pathogen. Chapter 3 addresses the in vitro effects of the ECP upon specific splenic immunocyte functions, phagocytosis and respiratory burst activity, in brook trout (Salvelinus fontinalis). The immune-complex mediated hypersensitivity reported to occur with BKD has considerable ramifications for control measures involving immunostimulation via antigen exposure. Further investigation is warranted to discern the significance and consistency of immunological hypersensivity in BKD pathogenesis. Chapter 4 examines the renal lesions, including immunopathologic changes and indications of immune-mediated disease, of brook trout exposed to R. salmoninarum.
- Book Review - Anaesthetic and Sedative Techniques for Aquatic Animals, Third EditionSmith, Stephen A. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2009-06-01)
- Book Review: Aquaculture Biosecurity: Prevention, Control, and Eradication of Aquatic Animal DiseaseSmith, Stephen A. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2008-06-01)
- Commercial Fish & Shellfish Technology Fact Sheet: Dealing with Trichodina and Trichodina-like SpeciesSmith, Stephen A.; Schwarz, Michael H. (Virginia Cooperative Extension, 2009-05-01)Provides information on what Trichodina and Trichodina-like species are, why they are a problem in aquaculture, and how they can be controlled.
- Common Diseases of Cultured Striped Bass, Monrone saxatilis, and Its Hybrid (M. saxitilis x M. chrysops)Smith, Stephen A.; Pasnik, David J. (Virginia Cooperative Extension, 2010-06-10)Provides information about viral, bacterial, fungal, and parasitic pathogens that healthy striped bass can become susceptible to when they are immunocomprised as a result of stress from aquaculture environments.
- Common Diseases of Cultured Striped Bass, Morone saxatilis, and Its Hybrid (M. saxitilis x M. chrysops)Smith, Stephen A. (Virginia Cooperative Exension, 2020-06-19)Infectious diseases are a common cause of fish loss in aquaculture, often leading to the demise of the entire fish population. Therefore, an understanding of potential pathogens of striped bass and their hybrids and early disease recognition is critical to prevent significant losses (McAllister, Mann, and McKenzie 1987).It is also important to understand that many disease outbreaks are caused by opportunistic pathogens and thus can be prevented by proper husbandry and management techniques.
- Comparative Growth of All-Female Versus Mixed Sex Yellow Perch (Perca flavescens) in Recirculating Aquaculture SystemsSchmitz, Mark Harvey (Virginia Tech, 1999-05-20)Nine, production-scale, recirculating aquaculture systems were utilized to compare the growth parameters between all-female and mixed sex yellow perch stocks. Each system was stocked with 455 fish m⁻³ and contained one of three different biofilter types: a rotating biological contactor, a trickling filter or a bead filter. The all-female fingerlings (S1) used were originally derived from Lake Mendota, Wisconsin. The mixed-sex fingerlings (S2) used were originally derived from Lake Erie. Temperature and photoperiod (23°C, 16H-L) were maintained at levels for optimal growth. Absolute growth rates ranged from 0.27-0.48 g/day. Mean final density within treatments was 42.8 kg/m³ and ranged from 37.2-50.2 kg/m³. The main effect of stock did not have a significant effect on growth (p > .1). All-female treatments exhibited more uniform growth. The main effect of filter type did have a significant effect on fish growth (p < .01), with fish in tanks containing trickling filters exhibiting significantly higher growth. Total feed conversion averaged 1.61 across all treatments and ranged from 1.38-1.78. S1 treatments consumed a significantly higher percent body weight per day than S2 treatments (p < .05). Analysis of PIT tagged individuals revealed that the mean relative growth rate was significantly higher in S2 individuals (513.9%) compared to S1 individuals (315.3%: p < .01). S2 females (597.8%) grew 1.9 times faster than S1 females (315.3%: p < .01). Within S2 individuals, females (597.8%) grew 1.5 times faster than males (395.2%: p < .05). For all individuals, 33.6% of the variation in final weight was explained by the variation in initial weight. Differences in the geographic strain or culture history of these stocks may have had a larger overall effect on growth than sexual classification (all- female or mixed sex). Dress percentage of skin-on butterfly fillets was examined in 20 individuals per stock and in six groups of 20 individuals per stock. Within S2 individuals, 73.7% were female. Mean fillet yield was significantly greater in S1 individuals (47.6%) compared to S2 individuals (43.0%: p < .01). Mean GSI in S1 individuals (1.01%) was significantly higher than S2 individuals (0.54%: p < .05). Within S2 individuals, mean GSI was significantly higher in females (0.70%) when compared to males (0.08%: p < .05). Fillet yield was significantly greater in S1 groups (47.2%) compared to S2 groups (44.9%: p < .01). Within each stock fillet yield increased with size. The difference in fillet yield demonstrated between these stocks may be a result of differences in strain of origin. The identification of superior yellow perch strains or strain crosses with regard to growth rate and fillet percentage is of considerable importance to the industry.
- Comparative Pharmacokinetics and Tissue Concentrations of Flunixin Meglumine and Meloxicam in Tilapia (Oreochromis spp.)Martin, Miriam; Smith, Stephen A.; Kleinhenz, Michael; Magnin, Geraldine; Lin, Zhoumeng; Kuhn, David; Montgomery, Shawnee; Coetzee, Johann (MDPI, 2021-11-25)Evidence of pain perception in fish is well established, but analgesic use in aquaculture is limited. The objective was to investigate the comparative pharmacokinetics of flunixin administered intramuscularly (IM) and meloxicam administered IM or orally (PO) in tilapia. Two hundred and seventy fish were assigned to 1 of 3 treatment groups: flunixin meglumine IM (2.2 mg/kg); meloxicam IM (1 mg/kg); or meloxicam PO (1 mg/kg). Blood and tissue samples were collected from 6 fish per treatment at 14 time points for 10 days. Drug concentrations were determined using ultra-high-pressure liquid chromatography coupled with mass spectroscopy. Plasma concentration versus time data were analyzed with a non-compartmental approach using a commercially available software. Flunixin reached a mean maximum concentration (Cmax) of 4826.7 ng/mL at 0.5 h, had a terminal half-life (T1/2) of 7.34 h, and an area under the concentration–time curve extrapolated to infinity (AUCINF_obs) of 25,261.62 h·ng/mL. Meloxicam IM had a T1/2 of 9.4 h after reaching a Cmax of 11.3 ng/mL at 2 h, with an AUCINF_obs of 150.31 h·ng/mL. Meloxicam PO had a T1/2 of 1.9 h after reaching a Cmax of 72.2 ng/mL at 2 h, with an AUCINF_obs of 400.83 h·ng/mL. Tissue concentrations of both drugs were undetectable by 9 h. Flunixin reached a sufficient plasma concentration to potentially have an analgesic effect, while meloxicam, when administered at the given dosage, likely would not.
- Comparisons of tilapia seed production under various broodstock densities and fry stocking densitiesGlenney, Gavin W. (Virginia Tech, 1996-12-10)Four methods of seed (eggs, sac-fry, and fry) production for Rocky Mt. White hybrid® tilapia, (0. niloticus x O. aureus), were compared under green water conditions over a six month period in an environmentally controlled greenhouse at the Virginia Polytechnic Institute and State University's Aquaculture Research Laboratory. Twelve 3 m2 rectangular tanks were stocked with brood stock (mean wt. 680 g), at a sex ratio of 3 females to 1 male. Nine tanks were stocked at one of three densities (1, 2, and 4 females m-2), and seed was collected from females' mouths weekly. Three additional tanks were stocked at a density of 2 females m-2, and fry were collected from the edges of the tanks when seen. Seed production was among the highest seen for related studies. Average number of viable fry produced at I females m-2, 1660 fry female- I month-I, was significantly higher than the combined average production of densities 2 females m-2 (629 fry female- I month-I) and 4 females m-2 (695 fry female-1 month- 1) (p< 0.02). Even though there was no significant difference between viable fry production meter-2 (p>0.05), the highest density consistently produced more fry meter-2. No significant difference was observed in viable fry production between the two seed collection methods (Clutch removal- 629 fry female-1 month-I; Natural mouth-brooding- 520 fry female-1 month-I) (p>0.05). The effects of stocking density on growth and survival were evaluated by stocking 14-16 day old artificially incubated fry (25.5 ± .32 mg, 12.1 ± .04 mm), into 150 liter troughs at three densities (3, 6, and 12 fry liter-I) under green water conditions for 30 days. The mean monthly hatchery seed survival was 65.7 ± 2.3%, which varied largely depending on initial seed developmental stage. Significant differences were observed between mean weight, length, survival, and feed conversion ratios among the various fry stocking densities (p
- Dealing with Trichodina and Trichodina-like speciesSmith, Stephen A.; Schwarz, Michael H. (Virginia Cooperative Extension, 2019-02-22)Discusses several species of protozoan parasites of fish, their life cycles, how they affect fish, and methods of treatment.
- The Development and Application of a Hemolytic Plaque Forming Cell Assay (PFC) and a Cytotoxic T-Lymphocyte Assay (CTL) in Tilapia (Oreochromis niloticus) for Immunotoxicity Risk Assessment of Environmental ContaminantsSmith, Dorinda Ann (Virginia Tech, 1998-07-24)The prospect of utilizing the cichlid teleost tilapia (Oreochromis niloticus) as an alternative experimental model to mammals for immunotoxicity risk assessment is currently being proposed. As such, the National Toxicology Program's (NTP) standard battery of rodent immunotoxicity assays is being developed for use in this fish species. Included in the testing series are the hemolytic plaque forming cell (PFC) and the cytotoxic T-lymphocyte (CTL) assays, quantitative indicators of antibody production and cell-mediated activity, respectively. The assays were modified in consideration of specific tilapian immune parameters, then tested using fourteen environmental contaminants or drugs, ten of which are classified by the NTP as immunotoxic in rodents. Reduced antibody production via a decrease in plaque number was observed in response to exposure of tilapia to eight of the nine humoral immunotoxicants, and five of the five non-immunotoxicants. Under specific immunization circumstances, immunostimulation (also a response to immunotoxicity) was noted via an increase in plaque number in benzo[a]pyrene (B[a]P) exposed fish using the PFC assay, a result noted in rodents as well. Reduced T-cell recognition and lysis of allogeneic tilapian lymphocytes via a decrease in the percentage of specific 51Chromium (51Cr) release was observed in response to exposure of tilapia to the nine of the ten cell-mediated immunotoxicants, and four of the four non-immunotoxicants. Although the normal teleost immune responsiveness was slightly weaker than seen with mice under comparable conditions (presumably due to differences in antibody structure and decreased cells counts), tilapia were found to exhibit well-defined humoral and cell-mediated immune responses, and responses to immunotoxic and non-immunotoxic chemicals comparable to the rodent model.
- Development and Application of Non-Traditional Vertebrate Models to Investigate Terrestrial Ecological Risk to 2,46-Trinitrotoluene ExposureJohnson, Mark Steven (Virginia Tech, 1998-12-08)Assessing ecological risk to wildlife exposed to anthropogenic contamination in soil has traditionally been problematic. Attempts to standardize an approach to evaluate risk for various community types in North America have been challenging, given the variation in terrestrial communities and the values in which policy makers are bound to protect. This has resulted in vague, yet flexible guidance from the U.S. Environmental Protection Agency and other interested parties (e.g., the U.S. Army Corps of Engineers, and the Tri-Service Ecological Risk Assessment Working Group). Interpretation of these and other guidance has been variable, often resulting in conflicting opinions on how best to address the question of ecological risk to receptors that are exposed to xenobiotics in a soil matrix. This work reports the results of research designed to address the question of ecological risk to terrestrial vertebrates. Objective, ecologically-relevant criteria were used in the selection and development of models in this research. Several lines of logic were considered: 1) substance sensitivity, 2) ecological sensitivity (i.e., the species importance to the system; e.g., keystone species); and, 3) probability and extent of exposure. A primary soil contaminant at many U.S. Army installations is 2,4,6-trinitrotoluene (TNT). This was a result of the mass manufacturing, storing, and assembly of weapons from the early 1900's until the 1950s. The Army has reported soil concentrations of TNT ranging from 0.12 to 38,600 ug/g (Walsh and Jenkins 1992) and 0.08 to 64,000 ug/g (Hovatter et al. 1997). The chemical-physical properties of TNT result in a relatively unique compound, not easily amenable to current modeling techniques to estimate exposure to terrestrial wildlife. Moreover, there are few data describing the effects of exposure to TNT in other than mammals, fish, and specific invertebrates. In this research, the pathways of exposure and selected potential toxic effects from TNT exposure were investigated in a terrestrial salamander: Ambystoma tigrinum (tiger salamanders). A. tigrinum was chosen since they are exclusively carnivorous, relatively long-lived, have a thin integument, and are large enough to investigate individual effects. These investigations were designed to mimic natural conditions as closely as possible, though maintain a degree of homogeneity in a laboratory environment. All studies exposed salamanders to soil and food (earthworms) in identical preparations. As such, these exposures were considered complete, eliminating assumptions made regarding daily food consumption, systemic dermal dose, etc. The first study examined the relative contribution of dermal or oral exposures to the whole-body burdens of TNT and primary metabolites. A poly-chlorinated biphenyl (PCB) mixture (Aroclor7 1260) was used with TNT to simultaneously to assist in the evaluation of each pathway, since the fate and transport of PCBs are well characterized. Tiger salamanders were exposed 28 days in situ. The dermal route of exposure contributed the most to the final burdens of TNT in salamanders, with the primary reduction products, 2-amino-4,6-dinitrotoluene and 4-amino, 2,6-dinitrotoulene reaching higher concentrations than of parent compound. Other TNT metabolites were found in insignificant quantities. The concentrations of PCBs were higher in the oral treatment, as expected. These results were corroborated in a subsequent study using Ambystoma maculatum (spotted salamanders). The second series of investigations evaluated the potential toxic effects from TNT exposure. Two treatments consisting of TNT and a control were used to evaluate these effects to A. tigrinum. The salamanders were exposed in situ for 14 days to TNT in soil and food (earthworms of which were exposed to TNT in the soil in similar preparations). Non-specific immune effects were evaluated through the characterization of splenic phagocytes in their ability to: 1) phagocytize foreign particles, and 2) digest (through oxygen radicals) phagocytized material. This was conducted using fluorescent microspheres and a fluorescent chemical probe specific to hydrogen peroxide, measured per each cell using flow cytometry. Other data collected included histological examination (e.g., liver, kidney, and other miscellaneous organs), blood differentials, weight changes over time, organ/ body weight comparisons, and an analysis of organ-specific metabolism. No significant effects were noted in salamanders exposed to these conditions. Coordinated with the preceding study included a search for biomarkers of exposure and an investigation of the metabolites of TNT in situ. Biotransformation products of TNT were found including primary (e.g., 2-amino-4,6-dinitrotoluene) and secondary (e.g., 2,4-diamino-6-nitrotoluene) in relative concentrations in skin, liver, and kidney. Biomarkers of exposure included an analysis of cytochrome p450, b5, and the glutathione antioxidant enzymes in liver, kidney, skin, lung, and serum, respectively. Traces of parent compound were found in the skin and liver only. Levels of 2,4-diamino-6-nitrotoluene were found only in the liver and kidney, suggesting that TNT is reduced primarily in or on the skin. Levels of p450 were higher in TNT exposed salamanders than controls. Glutathione and related enzyme levels are reported. This work suggests that salamanders have levels of detoxification enzymes capable of the biotransformation of anthropogenic substances in soil rivaling that of mammals. Another investigation evaluated these same immunological parameters in white-footed mice (Peromyscus leucopus). This species was chosen based on the relative importance of small mammals to the community structure in many North American ecosystems. Mice were exposed to TNT in the feed at 0.264, 0.066, 0.033, and 0.017%, where actual daily dose estimates for males were 604, 275, 109, and 65; and for females was 544, 282, 143, and 70 mg/kg/d. An investigation to evaluate the specificity of commercially-available monoclonal antibodies specific to cell surface markers for thymocytes and splenocytes in inbred mice was unsuccessful. These results suggest the recognition epitopes of monoclonal antibodies prepared against Old-World mice are not conserved into Peromyscus, a New-World species. However, high dose males and females had larger spleens consistent with the hemolytic effects previously reported for mammals exposed to TNT. Further, males exposed at all levels had reduced phagocytic activity of splenocytes, and reduced hydrogen peroxide production associated with the two highest doses relative to controls. Females showed no response relative to treatment. This research has shown the feasibility for these types of investigations, and provides toxicity information valuable for modeling estimates of ecological risk. Further, the in situ exposures have provided media concentrations that are or are not toxic for species of concern. This type of information reduces the uncertainty associated with ingestion modeling estimates, dermal exposure estimates, and other factors not traditionally considered in toxicity studies.
- The Effects of E-Beam Irradiation, Microwave Energy and High Hydrostatic Pressure on Presence and Health Significance of Cryptosporidium parvum in Eastern Oysters (Crassostrea virginica)Collins, Marina V. (Virginia Tech, 2005-02-09)Foodborne disease outbreaks associated with the protozoan parasite Cryptosporidium spp. are an emerging public health concern. Shellfish, including Eastern oysters (Crassostrea virginica) in Chesapeake Bay and other Atlantic coastal waters, have been identified as a potential source of Cryptosporidium parvum infection for humans. The inactivation of C. parvum and other pathogens in raw molluscan shellfish would provide increased food safety for normal and at-risk consumers. The objectives of this study were to evaluate the efficacy of three alternative food-processing treatments (e-beam irradiation, microwave energy, and high hydrostatic pressure processing) on the viability of C. parvum oocysts in Eastern oysters. Oysters were artificially infected with the Beltsville strain of C. parvum and subjected to the three treatments in separate experiments. The effects of the treatments were evaluated by inoculation of the processed oyster tissues using the neonatal mouse bioassay. E-beam radiation of in-shell and shucked oysters treated with doses of 1.0, 1.5 or 2.0 kGy produced significant reductions (P < 0.05) in C. parvum mouse infectivity. A dose of 2.0 kGy completely terminated the infectivity of C. parvum and did not adversely affect the visual appearance of the oysters. Microwave treatments of shucked oysters at time (temperature) exposures of 1 sec (43.2°C), 2 sec (54.0°C), and 3 sec (62.5°C) produced a reduction in C. parvum mouse infectivity of 26.7%, 33.3%, and 46.7%, respectively. Microwave treatments at 2 sec (54.0°C) and 3 sec (62.5°C) showed extensive changes in oyster meat texture and color. Thus due to lack of efficacy and unacceptable tissue changes, microwave treatment of oysters is not considered a viable food processing method. High pressure processing of shucked oysters at all pressures tested (305 MPa, 370 MPa, 400 MPa, 480 MPa, 550 MPa) significantly (P < 0.05) reduced infectivity of C. parvum oocysts as measured by the neonatal mouse bioassay. A treatment of 550 MPa at 180 sec produced the maximum decrease of C. parvum infectivity (93.3%). The results indicate that HPP (high pressure processing) can produce significant (P < 0.05) reductions in infectivity of C. parvum oocysts. Measurement of tristimulus color values of pressurized raw oysters at extended processing times from 120 sec to 360 sec at 550 MPa showed an increase (P < 0.05) in whiteness. One (e-beam irradiation) of the three food-processing treatments shows promise for commercial applications to reduce public health risks from cryptosporidiosis in Eastern oysters.
- Effects of High-density Stocking in a Recirculating Aquaculture System on Gill Morphology ofHybrid Striped Bass (Morone saxatilis x M. chrysops)Smith, B. J.; Smith, Stephen A.; Pfeiffer, Carl J. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2000-06-01)The types and distribution of gill lesions observed in hybrid striped bass (Morone saxatilis x M. chrysops) reared in a commercial-scale recirculating aquaculture system are described. When placed in the system as fingerlings and reared there for eight months at typical stocking density, the gills of all examined fish presented a variety of extensive, non-specific lesions typically resulting from poor water quality. Lesions included epithelial cell hyperplasia, infiltration of the interfilamental region by mixed inflammatory cells, hyperplasia of mucous and lamellar epithelium, lamellar fusion and occasional filamental fusion. Up to 76% of the gill sample surface of individual fish was affected, with lesions being most severe in the distal filamental regions. Fish transferred to and maintained at low stocking densities in water of superior quality demonstrated that all lesions were fully reversible by five weeks post-transfer. This study demonstrates that culture of hybrid striped bass under intensive aquaculture management induced pathological changes in the gills, and suggests that maintenance of fish under improved water quality conditions will reduce gill lesions, which could potentially increase the fishes' performance.
- The effects of temperature, water quality and culture conditions on the immunology, hematology, and blood chemistry of hybrid striped bassHrubec, Theresa (Virginia Tech, 1994-12-19)Sunshine and palmetto bass (different crosses of hybrid striped bass) were used to determine immunologic, hematologic and serum chemistry changes under different culture conditions. The kinetics of the humoral immune response was determined for sunshine bass acclimated to 10, 18, 24, 29°C, and to elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). These conditions are frequently encountered in aquaculture situations. Cooler temperatures decreased both the magnitude and onset of the humoral response, being lowest at 10°C, intermediate at 18°C, the highest at 24 and 29°C. Elevated ammonia did not affect the immune response, while elevated nitrate decreased antibody production to the level of the 18°C response. Hematologic reference intervals were determined for sunshine bass in tanks and recirculating systems, and palmetto bass in tanks. Serum chemistry reference intervals were determined for sunshine bass in tanks, recirculating systems and cage systems. Greater differences were observed in reference intervals between the culture systems, than between the two types of hybrid. To determine if environmental factors influenced the differences seen in the reference, sunshine bass were acclimated to 10, 18, 24, 29°C, elevated ammonia (0.15 mg/L NH3) and elevated nitrate (200 mg/L). The hematology and serum chemistry profiles of these fish were compared with the reference intervals for sunshine bass in tanks. Leukocyte, lymphocyte and monocyte counts at 10°C, and glucose and calcium at 10 and 18°C deviated sufficiently to suggest generating separate reference intervals at these temperatures. In the nitrate treated fish, creatinine levels were elevated and chloride levels were lower than controls and outside the reference interval. These two responses were presumed to be pathologic changes associated with elevated nitrate levels due to the large deviation in the analytes and the mortalities seen in the nitrate treated fish. The remaining analytes for fish in the different environments were within or slightly outside the reference intervals. These slight changes were presumed to be due to individual variation as the reference intervals were determined for fish under relatively uniform conditions and may not be sufficiently broad to cover fish from more varied environments. With minor modification, the reference intervals should apply to sunshine bass in most situations.
- Enhancing Seafood Quality and Safety by Reducing Reliance on Antibiotics: Applying a Novel Antibody in TilapiaGarry, Jordan Nicole (Virginia Tech, 2018-06-14)Disease outbreaks have overwhelmed the aquaculture industry as a whole and have been catastrophic for many single operations. To minimize disease outbreaks, efforts are underway to enhance animal health and disease resistance to pathogens without the use of antibiotics. The overall purpose of this study was to explore a potential prophylactic, a novel antibody diet, for the bacterial pathogen, Aeromonas hydrophila, in tilapia. The tilapia were on an anti-interleukin-10 antibody diet as a neutralization of interleukin-10 (IL-10), an anti-inflammatory cytokine. The anti-inflammatory function of IL-10 has been shown to allow persistence of gastrointestinal pathogens. Tilapia were fed the novel diet and were challenged via bath immersion or oral gavage with A. hydrophila. Four trials of challenge studies were conducted. Clinical signs of the disease and survival were monitored post-challenge of the bacteria. Out of the 4 trials, one bath immersion trial showed significantly lower survival in the group fed the novel antibody diet (p=0.044) compared to the control fed group, after challenged with A. hydrophila. The other trials tested showed no significant differences in survival between diets. Among the survival percentages collected as a whole, it cannot be determined from in vivo results whether this anti-IL-10 diet is effective in preventing mortality from A. hydrophila in tilapia. Therefore, an in vitro study using an enzyme-linked immunosorbent assay (ELISA) was used to determine the neutralization capability of anti-IL-10 on IL-10 using tilapia splenocytes. Interferon-γ, a pro-inflammatory cytokine, was quantified in order to find a trend in expression of IL-10 in vitro in various tilapia cell treatments. The protocol for the ELISA study is under development being that the use of this antibody is novel and has never before been done in fish.
- Establishment and Utilization of Tools for Enhancing Foodfish HealthGalagarza, Oscar Andres (Virginia Tech, 2018-01-29)Aquacultured products assist the human demands for seafood so that foodfish supplies can remain sustainable and consistent. Although the fish-farming industry has seen dramatic growth and intensification in recent years, the latter has led to an increase in bacterial diseases and fish health management problems, resulting in major economic losses around the world. In addition to the lack of understanding of fish physiology, these complications are exacerbated by the inappropriate and controversial use of antibiotics. This work addressed these issues in striped catfish (Pangasius hypophthalmus) and Nile tilapia (Oreochromis niloticus), two economically important foodfish, by investigating alternative, more cost-effective options to promote fish health. The first two studies established reference intervals for immunology, hematology and plasma chemistry analytes in striped catfish in a recirculating aquaculture system (RAS). In a third study, the immunomodulatory effects after directly feeding probiotic strains of Bacillus subtilis NZ86 and O14VRQ in Nile tilapia were ascertained. This last study revealed that supplementation with both of the probiotic strains for 51 days stimulated several local and systemic innate immune responses of tilapia. When these transient probiotic bacteria were present in the gut, a pro-inflammatory environment was developed as evidenced by the localized higher expression of the cytokines tumor necrosis factor (TNF) – α and interleukin (IL) – 1β. Significant increases (p < 0.05) were noted differentially by both probiotic strains throughout the trial in plasma lysozyme content, alternative complement activity, and in the peripheral blood leukocyte profiles. Additionally, there were trends for increased levels of phagocytosis and respiratory burst in leukocytes of the anterior kidney and spleen at the end of the trial, suggesting the potential use of these probiotic strains for improved immune-competence. These findings help to understand and clarify the potential mechanism of action associated with the increased disease resistance recorded in preliminary studies with the same probiotic strains. Implementation of the tools established and validated in this work could be useful in evaluating fish welfare situations involving striped catfish grown in RAS conditions, and also show promise for a healthier foodfish supply where antibiotic applications practices could be minimized.
- Evaluation of ceftiofur sodium as a chemotherapeutic agent in grass carp (Ctenopharyngodon idella)Somjetlertcharoen, Amornchai (Virginia Tech, 2001-03-23)Ceftiofur sodium, a third generation cephalosporin, was studied to determine the potential of this drug as an alternative bacterial therapeutic agent for the aquaculture and ornamental fish industry. Grass carp, Ctenopharyngodon idella have been selected as the fish model for this study since they are a good representative for both foodfish and ornamental fish and are one of the major species grown worldwide. Pharmacokinetics of ceftiofur sodium after various routes of administration, histopathologic observations to detect possible toxic effects on the tissues involved in its metabolism and excretion, and the effects on the non-specific immune response were investigated in grass carp. For the pharmacokinetic studies, ceftiofur sodium was administered a single time to grass carp by four different routes : intracardiac (IC), intraperitoneal (IP), intramuscular (IM) and oral (PO) at a dosage of 8 mg/kg body weight. Serial blood samples were obtained and plasma samples were analyzed by high performance liquid chromatography for ceftiofur (as measured its metabolite, desfuroylceftiofur (DFC) and DFC-related metabolite concentrations). Disposition pharmacokinetic data were best described by a two compartment open model for IC and by a non-compartment model with no lag time for IP and IM administrations. Oral absorption of ceftiofur was not observed in this species. Following IC, IP and IM ceftiofur sodium administration, the final elimination half-lives, maximum plasma concentration, time to reach maximum concentration, volume of distribution and plasma clearance were 0.38, 0.45 and 13.86 hours ; 157.09, 31.54 and 8.86 mg/ml ; 0, 0.25 and 0.5 hours ; 0.09, 0.17, 0.53 l/kg ; and 0.21, 0.26, 0.26 ml/min.kg, respectively. Desfuroylceftiofur metabolite was highly bound with plasma protein at pH 7.0 and 8.0. For the histopathological studies, a single intramuscular dose of ceftiofur sodium at three different concentrations, 8 (1X), 40 (5X) and 80 (10X) mg/kg was administered to separate groups of grass carp for evaluation of the potential toxicity to major tissues involved in metabolism and excretion of this drug. These included the anterior kidney, posterior kidney, liver, and spleen. After 48 hours, lesions were seen in the posterior kidney at the highest dose of ceftiofur (10X). Morphological alterations observed microscopically included increased number of renal tubules, tubular necrosis and infiltration of inflammatory cells. No adverse effects on the glomeruli were observed at any concentration of the drug. For the immunotoxicity studies on the non-specific immune response, dosages of either 8 or 40 mg/kg body weight were administered intramuscularly. After 24 and 48 h, leukocyte number, phagocytic ability and H2O2 production were examined in the cells of the pronephros. The results showed that neither dosage had an effect on the number of leukocytes in the pronephros. Phagocytosis was also not significantly altered at either dosage in macrophages from the pronephros. Hydrogen peroxide production was not altered in the pronephros of fish dosed at 8 mg/kg, while at a dosage of 40 mg/kg, H2O2 production was significantly increased. In summary, ceftiofur sodium has potential as an efficacious chemotherapeutic agent for controlling bacterial infection in brood stock and ornamental fish at the recommended dose of 8 mg/kg. A dose as high as 40 mg/kg can be use with careful consideration. This dosage may not directly injure the posterior kidney but it may affect the non-specific immune response of the fish.
- «
- 1 (current)
- 2
- 3
- »