Joseph M. Groff

Hematology and clinical chemistry of cyprinid fish. Common carp and goldfish.

Evaluation of the clinical status in aquatic species is compromised by the limited diagnostic techniques that can be performed in these species. The hematologic and plasma chemistry parameters can provide predictive information, although these parameters can be highly variable owing to the influence of various intrinsic and extrinsic factors. However, these parameters are fairly stable in acclimated, well-managed fish if stress is reduced during collection and samples are properly collected and analyzed. Evaluation of any single parameter is not predictive and, therefore, not recommended. Ideally, the diagnostic protocol should include evaluation of the hematologic indices, total and differential cell counts, TPP, glucose, sodium, and chloride. The practitioner who is routinely involved in aquatic animal medicine should consider in-house evaluation of these parameters.

Loma salmonae (Protozoa: Microspora) infections in seawater reared coho salmon Oncorhynchus kisutch

Abstract Loma salmonae (Putz et al., 1965) infections were observed in five groups of coho salmon, Oncorhynchus kisutch , reared in seawater net-pens in Washington State, U.S.A. in 1984–1986. Ultrastructural characteristics, size of spores, tissues and host infected, and geographical location identified the microsporidium as Loma salmonae . Preserved spores measured 4.4×2.3 (4–5.6×2–2.4) μm and exhibited 14–17 turns of the polar filament. Infections were evident in the gills of some fish before seawater entry, but few parasites were observed and they caused little tissue damage. Infections observed in fish after transfer to seawater were associated with significant pathological changes in the gills. A mixed inflammatory infiltrate was associated with ruptured microsporidian xenomas within the vessels and interstitium of the primary lamellae. Microsporidian spores were dispersed throughout the lesions and were often seen inside phagocytes. The parasite was also observed in the heart, spleen, kidney and pseudobranchs; however, the inflammatory lesions were common only in the heart. Monthly examination of fish after transfer to seawater showed peak prevalences (33–65%) of gill infections during the summer. Although moribund fish were often infected with other pathogens, the high prevalence of L. salmonae infections and the severity of the lesions it caused, suggested that this parasite significantly contributed to the recurrent summer mortalities observed at this net-pen site.

A Viral Epizootic in Cultured Populations of Juvenile Goldfish Due to a Putative Herpesvirus Etiology

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Isolation and Characterization of Flexibacter maritimus from Marine Fishes of California

Abstract Lesions of the head, body, eyes, and fins colonized by gliding bacteria were observed in four marine fish species along the southern California coast and described histologically. Chinook salmon Oncorhynchus tschawytscha reared in marine net-pens had severe gill lesions colonized by gliding bacteria. Gliding bacteria with a requirement for seawater were recovered from white seabass Atractoscion nobilis, northern anchovy Engraulis mordax, and Pacific sardine Sardinops sagax. Biochemical characterization showed that the gliding bacteria belonged to the species Flexibacter maritimus, the first identification of this bacterium along the Pacific coast of North America. Criteria for presumptive identification of F. maritimus include Gram stain morphology, motility, oxidase and catalase production, agar hydrolysis, seawater requirement, Congo red reaction, and flexirubin pigment.

Infectious Diseases Impacting the Commercial Culture of Salmonids

Abstract Similar to the production of any intensively managed species, the probability of disease in aquaculture species has a direct correlation to the intensity of the production system. Since diagnosis and treatment of diseases can greatly increase the cost of production, prevention of disease is the preferred management strategy in aquaculture enterprises. This review will discuss the infectious diseases of salmonids that are considered economically important due to their regional or international impact on commercial salmonid operations. This paper will also review proper diagnostic methods and techniques that are essential to any discussion of diseases, as well as aspects of disease epizootiology, pathogenesis, treatment, and preventive measures.

Epitheliocystis infection in cultured white sturgeon (Acipenser transmontanus): antigenic and ultrastructural similarities of the causative agent to the chlamydiae.

A mild to moderate branchial epitheliocystis infection was diagnosed in subyearling (11 months old, 250–300 g) white sturgeon (Acipenser transmontanus) from a private culture facility with a 4–8% mortality in the population. Infected branchial epithelial cells contained the coccoid to coccobacillary epitheliocystis organisms, which appeared as cytoplasmic inclusions composed of a fine, homogeneous, dense, basophilic, granular material. The infected cells were variably enlarged with spherical to oval profiles and were randomly distributed throughout the branchial epithelium. The cytoplasmic inclusions stained positive with Macchiavello stain but negative with Brown and Brenn, periodic acid-Schiff, and Gimenez stains. Expression of chlamydial antigen was demonstrated within the cytoplasmic inclusions using a standard peroxidase-antiperoxidase immunohistochemical technique. Three stages of coordinated intracellular development were recognized by electron microscopy. The reticulate bodies were oval to spherical and 0.4–0.8 × 0.5–1.4 μm but often exhibited a pleomorphic and convoluted appearance because of variable membrane invaginations and evaginations suggestive of uneven fission and budding. Separate host cells contained intermediate bodies that were spherical to oval and 0.2–0.4 × 0.3–0.6 μm although often observed in the process of apparent uneven division. The presence of a cap or plaque composed of hexagonally arrayed fibrillar surface projections was initially recognized in this stage. A homogeneous population of 0.3–0.4 μmoval elementary bodies were observed separately in individual host cells. This developmental stage had a single, dense, compact, eccentrically located cytoplasmic condensation that occurred opposite to the location of the cap of hexagonally arrayed fibrillar surface projections. Morphologic characteristics of the epitheliocystis organism in these white sturgeon were similar to those previously described in other teleosts and expands the species catalogue of epitheliocystis infection. Furthermore, the ultrastructural similarities to the chlamydiae and the immunohistochemical detection of chlamydial antigen provides further evidence that the epitheliocystis agent is related to members of the Chlamydiales. Although the infection was considered mild to moderate and could not be definitively attributed to the mortality in this population, the potential adverse impact of epitheliocystis infection on sturgeon culture should be considered especially in intensive fish culture operations.

Occurrence of white sturgeon iridovirus infections among cultured white sturgeon in the Pacific Northwest

Abstract The white sturgeon iridovirus (WSIV) was detected in cultured white sturgeon Acipenser transmontanus from the lower Columbia River in Oregon, the Snake River in southern Idaho and the Kootenai River in northern Idaho, USA. In Oregon, WSIV was consistently detected in young sturgeon that were progeny from Columbia River adults and cultured in river water but not detected in sturgeon cultured in well water. In Idaho, WSIV was detected in sturgeon that were progeny from wild Snake River and Kootenai River adults after being subjected to stressful conditions of low spring water flows and high fish densities. When densities were reduced and water flows increased, mortality subsided. These observations suggest that WSIV may occur in wild sturgeon and that the virus may be present in many Northwest populations due to the long life span of the species, migratory patterns, and continuity of the river systems. Additionally, since the disease appears size(age)-specific and stress-mediated, fish culture management strategies could be used to avoid or minimize epizootics. These include iodophor disinfection of eggs, sustaining low fish densities and loadings, maintaining virus-free water supplies, minimizing adverse environmental conditions, and reducing the handling of sturgeon younger than 1 year.

Toxicity and pharmacokinetics of the antibiotic fumagillin in yearling rainbow trout (Salmo gairdneri)

Yearling trout were administered fumagillin dicyclohexylamine (FDCH), an antibiotic that has shown promise for controlling myxozoan parasites in fish. FDCH was fed at 0.25 or 1 g/kg food at 1.5% body weight per day for 60 days, and gill, liver, kidney, spleen, thymus, intestine, and heart were examined histologically. In both treatment groups the hematopoietic tissue of the kidney and spleen was reduced and hematocrit was significantly lower relative to controls. No alteration was found in liver, intestine, heart, thymus, or gill. FDCH was also administered to trout through an indwelling catheter placed in the dorsal aorta. Plasma FDCH was measured using reverse-phase HPLC, and clearance microconstants were estimated. At the highest doses (60 and 30 mg/kg body wt) fumagillin was lethal within about 6 hr, and histological examination revealed extensive toxic alteration in liver and posterior kidney. Plasma clearance at 6 and 3 mg/kg fit a two-compartment model with a rapid alpha phase (i.e., 20 min) but a prolonged beta phase (5.4 days). Although these fish survived for at least 96 hr, renal tubular alteration remained.

Cytokeratin-filament expression in epithelial and non-epithelial tissues of the common carp (Cyprinus carpio)

Abstract.Cytokeratin expression in mammals is generally restricted to epithelial cells and has been utilized to differentiate epithelial from nonepithelial tissues in these species. Since cytokeratins have been shown to be highly conserved during vertebrate evolution, the objective of the present study has been to ascertain the expression pattern of cytokeratins in tissues of the common carp (Cyprinus carpio). A panel of 10 anti-human cytokeratin antibodies was evaluated using a streptavidin-biotin-peroxidase complex detection system. Tissues were fixed in 10% neutral-buffered formalin, 100% ethanol or methacarn. Only formalin-fixed tissues were pre-digested with trypsin prior to immunostaining. Formalin-fixed tissues generally resulted in a less intense, more diffuse staining pattern with considerable background compared with ethanol and methacarn and was therefore the least desirable fixative. The diverse staining pattern observed with the various antibodies used in this study was consistent with previous findings in other teleosts. The results confirm that cytokeratin expression in teleosts is fundamentally different from that in mammals and therefore should be used as a method to differentiate epithelial cell types in these species only with discretion.

Cutaneous Biology and Diseases of Fish

The normal structure and function of the piscine integument reflects the adaptation of the organism to the physical, chemical, and biological properties of the aquatic environment, and the natural history of the organism. Because of the intimate contact of fish with the environment, cutaneous disease is relatively more common in fish than in terrestrial vertebrates and is one of the primary disease conditions presented to the aquatic animal practitioner. However, cutaneous lesions are generally nonspecific and may be indicative of disease that is restricted to the integument or a manifestation of systemic disease. Regardless, a gross and microscopic examination of the integument is simple to perform, but is highly diagnostic and should always be included in the routine diagnostic effort of the aquatic animal practitioner, especially since various ancillary diagnostic procedures are either not practical or lack predictive value in fish. The purpose of this article is to provide an overview of normal cutaneous biology prior to consideration of specific cutaneous diseases in fish.