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J S Guy

Publications and source records attributed to J S Guy.

14 recordsLinked to original sources
PubMed1990

Reactivation of latent pseudorabies virus infection in vaccinated commercial sows.

Pseudorabies virus (PRV) was isolated from 9 of 44 PRV-vaccinated seropositive sows on 5 of 11 farms. Although serum-neutralization antibody titers were 1:16 to 1:256, 28 virus isolates were obtained from tonsil, nasal, or buccal swab samples from 9 sows given 2 ml of dexamethasone/kg of body weight IM for 5 days. Pseudorabies virus was isolated from 6 of 20 sows (3 of 5 farms) given a killed-virus vaccination. Virus was obtained from 3 of 24 sows (2 of 6 farms) given modified-live virus and killed-virus vaccination. Evaluation of the 9 PRV with 5 restriction endonucleases revealed 4 PRV existing genotypes. The 9 isolated types of PRV appeared to be indistinguishable by Kpn I and BamHI restriction endonuclease analysis; however, when analyzed with Sal I, HinfI, and Pst I, isolates 7 (farm D), 8 (farm C), and 9 (farm B) had numerous differences. Isolates 1, 2, 3, and 4 (farm F) and 5 and 6 (farm G) appeared to be the same genotype when further analyzed with Pst I, HinfI, and Sal I.

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PubMed1979

Bovine coronavirus genome.

The tissue culture-adapted strain (Mebus) of the bovine coronavirus was grown to titers of greater than 10(7) 50% tissue culture infective doses per ml in secondary bovine embryo kidney cells, and the RNA was isotopically labeled with [3H]uridine. The RNA was extracted from purified virus and was found to have the following properties. (i) It consisted primarily of a homogeneous large-molecular-weight species which comigrated electrophoretically with vesicular stomatitis viral RNA and therefore had an apparent molecular weight of 3.8 X 10(6). (ii) It remained as a 3.8 x 10(6)-molecular-weight molecule after heat denaturation when rapidly harvested virus was examined. (iii) It was 80% susceptible to pancreatic RNase A digestion in high (0.3 M) NaCl, and the 20% resistant fraction was 4S to 7S in size. (iv) It was polyadenylated to the extent that 40 and 60% of the native RNA bound to polyuridylic acid-Sepharose and oligodeoxythymidylic acid-cellulose, respectively, under conditions of high (0.5 M) NaCl.

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PubMedDate not supplied

Increased virulence of modified-live infectious laryngotracheitis vaccine virus following bird-to-bird passage.

Modified-live (ML) infectious laryngotracheitis (ILT) vaccine viruses, both tissue-culture-origin (TCO) and chicken-embryo-origin (CEO), were passaged 20 times in specific-pathogen-free chickens. After serial bird-to-bird passage, increased virulence was observed for CEO virus but not TCO virus. Increased mortality and increased severity and duration of respiratory disease were observed in chickens inoculated with chicken-passaged CEO viruses; only mild respiratory disease (no mortality) occurred in chickens inoculated with chicken-passaged TCO viruses. These findings suggest that ML ILT vaccine viruses may increase in virulence after bird-to-bird passage.

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PubMedDate not supplied

Partial characterization of a turkey enterovirus-like virus.

Small round viruses, 18 to 24 nm in diameter, were detected by electron microscopy in droppings of young turkeys with enteritis. The virus was propagated in embryonated turkey eggs and tentatively identified as an enterovirus based on size, intracytoplasmic morphogenesis, buoyant density of 1.33 g/ml in CsCl, and a single-stranded RNA genome of approximately 7.5 kb. It was distinguished from avian encephalomyelitis virus by cross-immunofluorescence. These results identify an enterovirus-like virus as a possible etiologic agent of enteric disease of young turkeys. However, its role in this disease remains to be established.

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PubMedDate not supplied

Virulence of infectious laryngotracheitis viruses: comparison of modified-live vaccine viruses and North Carolina field isolates.

Virulence of six modified-live (ML) infectious laryngotracheitis (ILT) vaccine viruses was compared with that of 11 field isolates (indistinguishable from vaccine viruses by DNA restriction endonuclease analyses) by intratracheal exposure of 4-week-old, specific-pathogen-free chickens. Virulence of ILT viruses was based on an intratracheal pathogenicity index, mortality, and tracheal lesions. Intratracheal pathogenicity indices for ML vaccine viruses ranged from 0.0 to 0.14, while those for field isolates were 0.20 to 0.82. Mortality was a consistent clinical feature of field isolates; all produced mortality, with seven of the 11 isolates causing two or more deaths per inoculation group. In contrast, only one of six ML vaccine viruses produced mortality (one death per inoculation group). In general, tracheal lesions were more severe in chickens inoculated with field isolates and were produced more consistently than in chickens inoculated with vaccine viruses. These studies indicate that virulence of ILT field isolates was greater than that of ML vaccine viruses. Together with previous restriction endonuclease analyses, these findings suggest the possibility that field isolates originated from ML vaccine viruses through reversion to parental-type virulence.

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