John A. Plumb

An Iridovirus Isolated from Wild Largemouth Bass

Abstract During July through September 1995, about 1,000 adult largemouth bass Micropterus salmoides died in Santee-Cooper Reservoir, South Carolina. Necropsy of two moribund largemouth bass (each weighing about 2 kg and measuring about 50 cm) revealed no parasites or bacterial infection. Fathead minnow (FHM) cell cultures inoculated with filtered homogenate from the swim bladder of one fish and the swim bladder and liver of the second fish developed cytopathic effect 48 h after inoculation. Media from infected cell cultures contained up to 108.9 TCID50/mL of a 0.45-μm filterable agent (TCID50 is the tissue culture infective dose that affects 50% of innoculated cultures). Electron microscopy of infected FHM cells revealed a cytoplasmic, icosahedral virion that averaged 132 nm from facet to facet and 145 nm from corner to corner. Viruses acquired an envelope upon passing through the plasma membrane. Studies of virus replication inhibition by pyrimidine analogs were inconclusive in classifying the nucleic a...

STREPTOCOCCUS SP. FROM MARINE FISHES ALONG THE ALABAMA AND NORTHWEST FLORIDA COAST OF THE GULF OF MEXICO

Abstract Fish kills in estuarine bays along the Florida and Alabama Gulf Coast were investigated in August and September 1972. Eight species of moribund fish were examined. A nonhemolytic, group B, type Ib Streptococcus sp. was isolated from over 90% of the fish examined. Parasites and toxicants were eliminated as possible causes of the kills.

Killing of Edwardsiella ictaluri by macrophages from channel catfish immune and susceptible to enteric septicemia of catfish.

The role of peritoneal macrophages in immunity to enteric septicemia of catfish (ESC) after infection with live Edwardsiella ictaluri was investigated. Channel catfish macrophage-mediated bacteriocidal activity was dependent on the macrophage:bacteria ratio. Ratios of 1:1 to 1:12 exhibited significant differences (P < or = 0.05) in killing between macrophages from immune fish when compared to killing by macrophages from susceptible fish at 2.5 h. At 5 h, macrophages from immune fish were capable of effective killing (83.3%) at a 1:24 effector:target ratio, whereas macrophages from susceptible fish killed significantly (P < or = 0.05) less (56.9%). Macrophage bacteriocidal activity was significantly greater (P < or = 0.05) in macrophages from individual immune fish (93.4%) compared to macrophages from individual susceptible fish (85.4%). The kinetics of macrophage killing showed a linear increase in bacteriocidal activity from 1 to 3 h. Opsonization with immune serum enabled macrophages from immune fish to kill bacteria more effectively (93.8 vs. 75.9%) at 2.5 h. Opsonization of E. ictaluri with immune serum significantly suppressed the killing ability of macrophages from susceptible fish (46.2%) at 2.5 h. The results suggest that macrophages from fish immune to ESC had a greater capacity to kill E. ictaluri than macrophages from susceptible fish especially when E. ictaluri were opsonized with anti-E. ictaluri antibody.

Morphological and Biochemical Properties of Four Members of a Novel Group of Reoviruses Isolated from Aquatic Animals

The morphological, biochemical and growth characteristics of four members of the Reoviridae, three from the fish hosts, golden shiner (Notemigonus crysoleucas), chum salmon (Oncorhynchus keta) and channel catfish (Ictalurus punctatus) and one from American oyster (Crassostrea virginica), were compared. Electron microscopy of negatively stained virions revealed icosahedral particles approximately 75 nm in diameter composed of a double capsid. Complete particles had buoyant densities in CsCl of 1.34 to 1.36 g/ml. The viruses replicated well in several fish cell lines, forming plaque-like syncytia in monolayer cultures. Each virus could be distinguished by the range of cell lines supporting its growth. Polyacrylamide gel electrophoresis showed that the genome of each virus was composed of 11 segments of dsRNA distributed among three size classes. There were three large, three medium and five small segments in each genome and each isolate had a unique electropherotype. The segments ranged from 2.5 X 10(6) to 0.31 X 10(6) mol. wt. with a total genome of approximately 15 X 10(6) mol. wt. Analysis by SDS-PAGE revealed that each virus had five major structural proteins. There were two large polypeptides of approximately 135,000 and 125,000 mol. wt., one medium size polypeptide of 70,000 mol. wt. and two small polypeptides of 45,000 and 34,000 mol. wt. Of the major structural proteins, those of approximately 70,000 and 34,000 mol. wt. were consistently present in the highest concentrations. Minor virion proteins were detected but were not characterized. These four viruses, isolated from aquatic animals, were unlike viruses of the six established genera of the Reoviridae.

Fish cell lines: establishment of a line from ovaries of channel catfish.

SummaryA cell line was established from the ovaries of a healthy, juvenile channel catfish,Ictalurus punctatus. These cells, designated CCO, have been passed 130 times during 3 years. The cells grow well in Eagles MEM-10 at a temperature of 30°C. Species of origin of the cells was confirmed by a cytotoxic dye exclusion test. The cells were found to be free of bacterial and fungal contamination. A study of chromosome preparations indicated that the karyotype is still in a state of flux. The CCO line replicated channel catfish virus but was refractory to 12 other viruses, 4 from fish, 1 from birds, and 7 from mammals.

Survival of Caught and Released Largemouth Bass after Containment in Live Wells

Abstract Survival of angled largemouth bass Micropterus salmoides held in live wells for 3–9 h, with and without a water conditioner, was compared to largemouth bass released within 30 min (immediate release) of capture. The study was set up to simulate conditions that may occur during a largemouth bass tournament. Simulated tournaments were held in August, November, February, May, and July. Survival of prerelease and postrelease fish was higher when water temperatures were cool during fall and winter. Survival of largemouth bass released within 30 min was 98.9%, which was higher (P < 0.01) than survival of fish held in live wells without a water conditioner (90.8%). Fish held for 3–9 h in live wells with a water conditioner had a 96.5% survival, which was higher (P < 0.05) than survival for those held in unconditioned water. Largemouth bass caught in July had higher mortality than fish caught in November, February, or May. Indications are that addition of a water conditioner to live wells enhances surviv...

Olfactory Organ of Channel Catfish as a Site of Experimental Edwardsiella ictaluri Infection

Abstract Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC), is one of the most important pathogens to infect channel catfish Ictalurus punctatus. Although the full pathogenesis of E. ictaluri is unclear, the olfactory organ is thought to be a site of entry. We have examined the effects of applying E. ictaluri directly into the olfactory capsule of channel catfish. Olfactory organs of 30 experimental fish were exposed to E. ictaluri for 1 h (1 mL, 1 × 106 colony-forming units/mL). Live fish were sampled at 1, 24, 48, and 72 h, and days 5 and 14 postinfection, and their olfactory organs were examined by light and electron microscopy. Damage, including loss of sensory cilia and microvilli from the olfactory mucosal surface, was observed at 1 h postinfection. Degeneration of olfactory receptors and supporting cells was evident by 24 h postinfection. The nonsensory region also showed signs of degeneration, such as columnar cells lacking cilia. Electron microscopic immunocytochem...

Virulence of different isolates of Aeromonas hydrophila in channel catfish

Abstract The virulence of nine Aeromonas hydrophila isolates from diseased fish, diseased Macrobrachium (freshwater shrimp) and from pond water was determined in channel catfish (Ictalurus punctatus) fingerlings. According to the lethal dose − 50% end point (LD50) of each isolate, the water organisms were significantly (P

Pathogenicity of a non-haemolytic Group B Streptococcus sp. in gulf killifish (Fundulus grandis Baird and Girard)

Abstract Gulf killifish ( Fundulus grandis ) were injected intraperitoneally with different bacterial concentrations and the LD 50 were 1.4 × 10 4 at 96 h and 7.5 × 10 at 168 h. No deaths occurred among fish dipped in the bacterial suspension for different time periods or when the fish were exposed to a 50 parts per thousand hyperosmotic solution prior to dip. Fish became infected when they were injured prior to dipping in the bacterial suspension, but crowding and low oxygen concentration did not precipitate infection. No deaths occurred with oral administration of the bacteria. Bacterial count per gram of tissue was determined for both liver and spleen of infected fish at four, 24-h intervals. There was a significant difference ( P > 0.12) between the bacterial counts at the different time periods.

Effect of Treatment with a Commercial Bacterial Suspension on Water Quality in Channel Catfish Ponds

Abstract Four channel catfish (Ictalurus punctatus) ponds were treated with a commercial bacterial suspension (Aqua-Bacta-Aid(R)) and four ponds served as controls. Concentrations of inorganic nitrogen, total phosphorus, chemical oxygen demand, 5-day biochemical oxygen demand, and chlorophyll α; numbers of bacteria and phytoplankters per milliliter; and percentages of blue-green algae did not differ significantly (P > 0.05) between treatments on any sampling date. On three sampling dates between mid July and mid August, there were significantly higher (P 0.1).