Evaluation of lethal and non-lethal sampling methods for the detection of white sturgeon iridovirus infection in white sturgeon, Acipenser transmontanus (Richardson)

Pectoral fin tissue of white sturgeon was investigated as a potential non-lethal sample source for the detection of white sturgeon iridovirus (WSIV) infection. Histopathology and polymerase chain reaction (PCR) results using fin tissue were compared with the standard lethal histopathology sampling method that utilizes head tissue. Tissues for each of the three sampling methods were collected weekly for 8 weeks from individual sturgeon undergoing an experimental cohabitation challenge with fish infected with the Abernathy isolate of WSIV. Non-lethal fin histopathological evaluation did not reveal infection during the first 3 weeks of sampling, while non-lethal PCR and the lethal method were variable. However, all three sampling methods were equally capable of identifying infection from 4 to 8 weeks post-exposure. Of the survivors tested, all were negative by PCR and the lethal method, and only one fish was identified as being positive by non-lethal fin histopathology. In another experiment, all three sampling methods were applied to asymptomatic WSIV carriers in a case study conducted at the Kootenai Tribal Sturgeon Conservation Hatchery. Results showed that both lethal and non-lethal fin histopathology were equally effective in detecting infection, but PCR was unable to identify this strain of WSIV. Depending on the virus isolate, these results suggest that non-lethal sampling of fin tissue (histopathology or PCR) is comparable with the lethal sampling method at identifying WSIV infection once infection is established, and under certain circumstances may provide an alternative to lethal sampling.     

Production of estradiol by each ovary during the estrous cycle of cows

The objective of our experiment was to examine changes in serum concentrations of estradiol in each utero-ovarian vein before, during and after gonadotropin surges. Four cows were given prostaglandin F2 alpha (PGF2 alpha) during diestrus and three cows were allowed to cycle spontaneously. All cows had a cannula in each utero-ovarian vein and in one jugular vein. Most cows had two transient rises in estradiol, primarily coming from a single ovary, preceding and after luteinizing hormone (LH) surges. The first rise in estradiol began after luteal regression and was sustained from 48 h before a pre-ovulatory LH surge to the end of the LH surge. The second rise in estradiol was sustained from 72 to 168 h after the end of an LH surge. To determine how rapidly asymmetrical production of estradiol began during luteolysis, several cows were injected with PGF2 alpha during the luteal phase. Blood samples were taken from a jugular and both utero-ovarian veins at hourly intervals before and after PGF2 alpha. Asymmetrical production of estradiol began within 3 h after an injection of PGF2 alpha. We concluded: (1) that a single ovary was responsible for the sustained increases in concentration of estradiol that occur during proestrus to estrus and early diestrus in cows and (2) that cows may have at least one follicle capable of producing estradiol during most days of an estrous cycle, thus little delay in selection of which follicle eventually ovulates occurs after luteal regression.     

The effect of phenothiazine on plasma prolactin levels in non-pregnant mares

Sixteen non-pregnant pony mares were divided into four groups of similar age and bodyweight (bwt). Groups were randomly assigned to one of four treatments consisting of oral administration of perphenazine (0.5 and 1.0 mg/kg bwt, phenothiazine (10 mg/kg bwt) and a control group. Blood samples were taken by jugular venepuncture and plasma prolactin concentrations measured using an homologous assay for equine prolactin. Analysis of variance was conducted on data designed as a split plot over time. Perphenazine given orally (0.5 and 1.0 mg/kg bwt) increased plasma prolactin concentrations when measured 3 and 6 h following feeding (P less than 0.05). Prolactin concentrations returned to normal by 11 h post drug administration. There was no response in plasma prolactin concentrations following oral phenothiazine treatment (10 mg/kg bwt). Perphenazine at the 1.0 mg/kg bwt level was discontinued after two days due to two mares exhibiting signs of hyperesthesia.     

Characterization of susceptibility and carrier status of burbot,Lota lota (L.), to IHNV,IPNV, Flavobacterium psychrophilum,Aeromonas salmonicida and Renibacterium salmoninarum

In this study, susceptibility and potential carrier status of burbot, Lota lota, were assessed for five important fish pathogens. Burbot demonstrated susceptibility and elevated mortality following challenge with infectious haematopoietic necrosis virus (IHNV) by immersion and to Aeromonas salmonicida by intraperitoneal (i.p.) injection. IHNV persisted in fish for at least 28 days, whereas A. salmonicida was not re-isolated beyond 17 days post-challenge. In contrast, burbot appeared refractory to Flavobacterium psychrophilum following intramuscular (i.m.) injection and to infectious pancreatic necrosis virus (IPNV) by immersion. However, i.p injection of IPNV resulted in re-isolation of virus from fish for the duration of the 28 day challenge. Renibacterium salmoninarum appeared to induce an asymptomatic carrier state in burbot following i.p. injection, but overt manifestation of disease was not apparent. Viable bacteria persisted in fish for at least 41 days, and bacterial DNA isolated by diagnostic polymerase chain reaction was detected from burbot kidney tissue 90 days after initial exposure. This study is the first to investigate susceptibility of burbot to selected fish pathogens, and this information will aid in efforts to culture and manage this species.     

An acute outbreak of equine dysautonomia (equine grass sickness) in a group of eight Przewalski's horses (Equus ferus [caballus] przewalskii)

Equine grass sickness (EGS) is a neurodegenerative disease affecting grazing equids of which a single case of the chronic clinical presentation has previously been reported in a Przewalski's horse (Equus ferus [caballus] przewalskii). A group of 8 Przewalski's horses were moved to a new enclosure, recently vacated by a group of 4 Eastern kiang (Equus kiang holdereri) that showed no evidence of disease. After 23 days the first Przewalski's horse showed clinical signs of acute EGS including flank sweating, belly kicking, rapid loss of body condition, cessation of faecal passage, nasogastric reflux and mouthing water. It was subjected to euthanasia within 48 h due to lack of therapeutic response. Within 24 h of this first case developing clinical signs, a further 5 Przewalski's horses showed similar clinical signs of acute EGS and were subjected to euthanasia. Post mortem examinations confirmed acute EGS, with all animals demonstrating typical chromatolysis, cytoplasmic hypereosinophilia, cellular swelling, vacuolation, pyknosis and loss of nuclei in approximately 90% of neurones in the cranial cervical and cranial mesenteric ganglia and myenteric and submucosal plexi of the ileum. Two Przewalski's horses within the group showed no clinical signs of disease. No single pathogen was identified as the causal agent, but the epidemiological pattern of the outbreak was typical for that previously reported for acute EGS in domestic equids. All affected animals and the 2 surviving Przewalski's horses had low antibody titres to Clostridium botulinum type C. This is the first report of acute EGS in a herd of Przewalski's horses.     

Proteins and antigens of Pasteurella multocida serotype 1 from fowl cholera.

The protein profiles of Pasteurella multocida serotype 1 isolates and the response of chickens to serotype 1 antigens were investigated using SDS-PAGE. Patterns obtained with Coomassie blue staining of soluble protein extracts were similar. The major difference between isolates was the position of one of the major proteins in the 34-38 kDa region. When chickens were experimentally infected with a clinical isolate of P. multocida serotype 1 various proteins were recognised by immunoblotting, including one with a relative molecular weight of 34 kDa; however, no reactions were observed in the region where LPS is known to migrate. When these infection sera were used in an EIA with purified LPS obtained from Heddleston serotype 1 type strain (X-73) they reacted strongly. Serum used for serotyping isolates in the gel diffusion precipitin test recognised many antigens in common with sera from infected birds, but some antigens were specific to typing sera.