In May 2006 a large mortality of several thousand round gobies Neogobius melanostomus (Pallas, 1814) occurred in New York waters of the St. Lawrence River and Lake Ontario. Necropsies of sampled fish from these areas showed pallor of the liver and gills, and hemorrhagic areas in many organs. Histopathologic examination of affected tissues revealed areas of necrosis and hemorrhage. Inoculations of fathead minnow Pimephales promelas (Rafinesque, 1820) cell cultures with dilutions of tissue samples from the necropsied gobies produced a cytopathic effect within 5 d postinoculation. Samples of cell culture supernatant were tested using RT-PCR and confirmed the presence of viral hemorrhagic septicemia virus (VHSV). Sequence analysis of the VHSV isolate resulted in its assignment to the type-IVb subgroup. The detection of VHSV in a relatively recent invasive fish species in the Great Lakes and the potential impact of VHSV on the ecology and economy of the area will require further investigation and careful management considerations. KEY WORDS: Viral hemorrhagic septicemia · VHSV · Round goby · New York State Resale or republication not permitted without written consent of the publisherDis Aquat Org 76: [187][188][189][190][191][192] 2007 lege of Veterinary Medicine, Cornell University. The fish arrived at Cornell in moribund or freshly dead condition and were processed for diagnostic evaluation. The second sample consisted of 9 dead round gobies collected on 15 May 2006 from Sandy Creek, Lake Ontario, west of Rochester, New York. These fish were transported on ice to the AAHP at Cornell University.Cape Vincent, St. Lawrence River samples. All moribund fish were euthanized with an overdose of MS-222 (tricaine methanesulfonate, Western Chemical) in water. Eight fish were processed for diagnostic evaluation. The remaining 15 fish were frozen whole at -20°C for future evaluation if necessary. The procedure for diagnostic evaluation is described by Noga (1996) and included collecting skin scrapings and gill clip samples, sterile collection of posterior kidney samples for bacteriology, gross pathology and collection of tissues for histopathology and virology. Samples of liver, kidney, spleen and gonad were collected in 2 pooled samples for detection of viral agents. The first pooled sample (Sample A) included tissues from gobies that were dead at the time of presentation. The second pooled sample (Sample B) included fish that were moribund at the time of presentation. These samples collected for virus isolation were processed as described in the following sections. Attempts at bacterial isolation consisted of cultures taken from the posterior kidneys that were streaked onto blood agar (TSA II 5% SB, BBL™, Becton Dickinson). These cultures were incubated for 7 d at 21°C. Samples of intestines, gut contents and liver were collected to test additionally for type-E botulism by PCR (Getchell et al. 2006).Irondequoit Bay, Lake Ontario samples. Five fish were processed for diagnostic evaluation. Skin scrapings, gill ...
The pharmacokinetics of intravenously and orally administered enrofloxacin was determined in fingerling rainbow trout (Oncorhynchus mykiss). Doses of 5 or 10 mg enrofloxacin/kg body weight were administered intravenously to 26 fish for each dose and blood was sampled over a 60-h period at 15 degrees C. Two groups of fish were treated orally with 5, 10, or 50 mg/kg (80 fish/dose at each temperature) and held at 15 degrees C or 10 degrees C during the 60-h sampling period. Following intravenous administration, the serum concentration-time data of enrofloxacin in rainbow trout were best described by a two-compartment open model for both doses of 5 and 10 mg enrofloxacin/kg. The hybrid rate constants alpha and beta did not differ between doses. The distributional phase was rapid with a half-life of 6-7 min for both doses. Overall half-lives of elimination were 24.4 h (95% CI = 20.2-30.8) and 30.4 h (24.2-41.0), respectively, for the 5- and 10-mg/kg doses. A large Vd(area) was observed following dosing of either 5 or 10 mg enrofloxacin/kg,: 3.22 and 2.56 l/kg, respectively. Whole body clearance for 5 mg/kg was 92 ml/h.kg and 58 ml/h.kg at the 10-mg/kg dose. Following oral administration, the serum concentration-time data for enrofloxacin were best described as a one-compartment open model with first-order absorption and elimination. Apparent Ka over all doses at 10 degrees C averaged 62% less than apparent Ka at 15 degrees C. Estimates of the apparent t(1/2)e over both temperatures ranged from 29.5 h (18.4-73.4) to 56.3 h (38.3-106.6). Bioavailability averaged 42% over all doses at 15 degrees C and was decreased to an average of 25% at 10 degrees C. Peak serum concentrations appeared between 6 and 8 h following dosing. A dose of 5 mg/kg/day was estimated to provide average steady-state serum concentrations at 10 degrees C that are approximately 4.5 times the highest reported MIC values for Streptococcus spp., the fish pathogen least sensitive to enrofloxacin. Owing to the long apparent half-life of elimination of enrofloxacin in fingerling trout, it would take approximately 5 to 9 days to achieve these predicted steady-state serum concentrations; this estimate is important when considering the duration of therapy in clinical trials.
The fluoroquinolone antibacterial family is a relatively recent group of bactericidal compounds, generally characterized by efficacy against a wide spectrum of bacterial organisms and exhibiting minimal adverse effects in treated patients. The fluoroquinolones are widely prescribed in both human and veterinary medicine, though in veterinary medicine in the USA there are currently only two approved compounds, enrofloxacin (Baytril, Bayer Animal Health, Shawnee Mission, KS) and sarafloxacin (SaraFlox, Abbott Laboratories, North Chicago, IL), both with limited species and disease label approvals. Currently, there are no approved fluoroquinolone antibacterials to treat bacterial infectious diseases in cultured fish species. Enrofloxacin was administered to juvenile Atlantic salmon as a single bolus via intraarterial (i.a.), intraperitoneal (i.p.), intramuscular (i.m.), or oral gavage routes of administration. The drug was administered via the first three routes to achieve a dose of 10 mg/kg, and via oral gavage to achieve both 10 (p.o.-10) and 5 (p.o.-5) mg/kg doses. Two-compartment model kinetics were observed with elimination of half-lives (t1/2) of 130.6, 34.32, 84.98, 105.11, and 48.24 h, area under the drug concentration-time curves (AUC) of 84.3, 75.31, 55.61, 41.68, and 38.81 micrograms x h/mL, and bioavailabilities (F) of 100, 89.34, 65.97, 49.44, and 46.04% (i.a., i.p., i.m., p.o.-10, p.o.-5, respectively). All administration routes at 10 mg/kg were found to yield comparable drug concentration-time curves for multiple tissue, indicating no distinct advantage of using one route over another from a kinetics perspective. Finally, the 5 mg/kg dose (p.o.-5) yielded comparable multiple tissue drug concentration-time curves to the 10 mg/kg dose (p.o.-10), providing pharmacokinetic evidence to justify therapeutic efficacy trials with the lower dose.
Previous researchers demonstrated that a mortality in fry (called Cayuga syndrome) of Atlantic salmon Salmo salar from Cayuga Lake (New York) was associated with low levels of thiamine. They reduced the mortality of fry by bathing or injecting fry with thiamine. We injected four to six gravid female Atlantic salmon with either physiological saline (PS) or PS plus thiamine (7 mg/kg weight) 14-23 d before eggs were stripped, fertilized, and incubated in individual lots. Chemical analyses showed that eggs from control and treated salmon contained 1.1 and 1.6 nmol thiamine/g, respectively. Thiamine injections had no significant effect on the percentage of eggs that hatched. Between 700 and 800 Celius degree-days postfertilization, control fry (saline) showed signs of Cayuga syndrome and a 45% incidence of mortality; in contrast, mortality was only 1.9% for fry that received thiamine. By 1,078 degree-days postfertilization, mean mortality of control fry was 98.6%, whereas that for thiamine-injected salmon was 2.1%. This study showed that thiamine injections of prespawning female salmon from Cayuga Lake increased thiamine content of their eggs and prevented the Cayuga syndrome and subsequent mortality of fry. Historically, overfishing, pollution, and building of dams and barriers to spawning migration were suggested as possible causes of the decline of the Atlantic salmon in Lake Ontario and Cayuga Lake. Based on our findings and other reports, we suggest another possible contributing cause of the extirpation of landlocked Atlantic salmon in Lake Ontario and some other inland waters of New York: the entrance of alewives Alosa pseudoharengus containing thiaminase, which induced thiamine deficiency in eggs and increased mortality in fry of the predatory salmon.Atlantic salmon Salmo salar, which were once
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