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Biomedical subjects

I M Parsonson

Publications and source records attributed to I M Parsonson.

At least 19 recordsLinked to original sources
PubMed1991

Temporal relationships of viremia, interferon activity, and antibody responses of sheep infected with several bluetongue virus strains.

Sheep had viremias that were first detected on day 3 (+/- 1) after infection with several strains of bluetongue virus (BTV) representing United States serotypes 10, 11, 13, and 17. Diphasic peaks of infectivity were attained on days 6 and 10 (+/- 2). Interferon (IFN) was first detected in serum samples on day 5 (+/- 1), and reached greatest concentrations on day 6 (+/- 2), which coincided with the first viremic peak; IFN concentrations then decreased toward zero by day 10 (+/- 2). Interferon peak concentrations induced approximately a 90% decrease in virus titer. The decrease in IFN concentrations by day 9 (+/- 2) corresponded with the second viremic peak on day 10 (+/- 2). Onset of the decrease in detectable concentrations of virus after the second peak of viremia corresponded to the initial detection of serum antibody to BTV by day 10 (+/- 2). Virus titer decreased and antibody production increased until approximately days 21 to 28, when the titers plateaued and virus was not detected. Febrile responses peaked on day 7 (+/- 1) during the peak viremic period. The WBC count was depressed at the time the virus titer increased, but returned to normal values while the sheep were still viremic. Diphasic viremias in BTV-infected sheep were attributed to induction of high concentrations of IFN concurrent with the first virus titer peak, followed by production of antibody to specific BTV strains and a subsequent reduction in viremia at the second virus titer peak.

Animals↗
PubMed1988

Maturation of immunological reactivity in the fetal lamb infected with Akabane virus.

The development of cell-mediated immunological reactivity was studied in fetal lambs infected with Akabane virus. Examination of hepatic cells from fetuses between 40 and 75 days' gestation that had been infected via the transplacental route revealed inconsistent responses to Akabane, together with a uniform failure to respond to non-specific mitogens which contrasted with the behaviour of control, uninfected lambs. Following direct inoculation of fetal lambs with virus between 50 and 120 days' gestation, specific proliferative responses were observed on the part of the spleen cells from some. Direct challenge of fetal lambs of 4 months' gestation evoked cellular responses in lymph draining from the site of virus inoculation similar to those produced by challenge of adult sheep. The proliferative response of lymph-borne cells was substantially better if live, rather than inactivated, virus had been used.

Animals↗
PubMed1988

Transmission of Akabane virus from the ewe to the early fetus (32 to 53 days).

The role of the placental junction in AKA virus infection in the ewe was examined during the time when the chorionic villi were first becoming firmly attached to the maternal caruncles. The studies were made over 21 days covering the period between 32 and 53 days of pregnancy. Viral tropism in the fetal membranes and tissues of the fetuses was identified by virus isolation and immuno-fluorescence studies. Areas of virus replication were noted from 24 h post-inoculation in the fetal membranes and persisted in these tissues throughout the experiment. Viral antigen was first detected in the fetus from day 5 post-inoculation by virus isolation and immuno-fluorescence. From this time on, viral activity increased in specific areas of the fetus, notably in the brain and, to a lesser extent, the skeletal muscles. Gross pathological changes occurred in the fetuses between day 14 and day 21 post-inoculation (46 to 53 days gestation). Despite the relatively high titres of AKA virus present in the placental tissues and the developmental changes occurring in the fetus due to the virus, the placental junction continued to carry out its physiological function of maintaining pregnancy.

Animals↗
PubMed1987

Experimental infection of bulls and cows with bluetongue virus serotype 20.

Bluetongue virus serotype 20 (BTV20) was inoculated intradermally and subcutaneously in 4 bulls and by the intrauterine route in 8 nulliparous cows after insemination at oestrus. Viraemia was detected intermittently between 8 and 21 days after inoculation. Virus was isolated from tissue samples of 2 cows and a bull after slaughter at 14 days and from one bull at 28 days. Group reactive and type specific antibodies to BTV20 were demonstrated from 17 to 27 days after infection. No antibodies were detected in the animals slaughtered at 14 days. No clinical signs of disease were seen during the experiment and no gross or histopathological changes referable to BTV20 infection were observed post-mortem. Because of the viraemia and the production of detectable serum antibodies, gametes from these cattle would be excluded from export.

Animals↗
PubMed1987

Bluetongue virus serotype 20: experimental infection of pregnant heifers.

Three groups of 4 cows at 84 to 95 days, 100 to 160 days, and 170 to 180 days pregnant were inoculated both intradermally and subcutaneously with bluetongue virus serotype 20 (BTV20). Clinical observations and the viraemic and serological responses of the cows were followed for 9 to 17 weeks after inoculation. Viraemia developed in 9 of the 12 cows and was first detected 4 to 9 days after inoculation. Viraemia was detected for 4 to 21 days and in some animals only intermittently. The titre of the viraemia was obtained in 4 cows and ranged from detectable only, to 10(1) to 10(2.8) 50% tissue culture infecting doses per ml. Both serum neutralising and precipitating antibodies were detected in 11 of the 12 cows within 2 to 8 weeks after inoculation. No clinical responses were seen and one cow (516) did not develop a viraemia or produce detectable antibodies to the virus. The cows, calves and foetuses were necropsied following either parturition or slaughter between 200 and 270 days of pregnancy. No virus isolations were made from a wide range of tissues from the cows, calves or foetuses and no immunoglobulins or serum neutralising antibodies were detected in the serums of precolostral calves or foetuses at necropsy. No gross or histopathological lesions were seen in the cows, calves or foetuses, and there was no evidence that BTV20 crossed the bovine placenta or infected the foetus.

Animals↗
PubMed1986

The pathogenicity of an avian influenza virus isolated in Victoria.

An influenza virus (H7N7) isolated from an outbreak of disease in chickens in Victoria, was examined for its ability to cause disease in inoculated chickens, turkeys and ducks. The virus was highly pathogenic in chickens and turkeys but produced no clinical disease in ducks. Transmission of infection occurred from inoculated chickens to those in direct contact but other chickens separated by a distance of 3m directly downwind developed neither clinical disease nor antibody to the virus.

Animals↗
PubMed1986

Responses of cattle, sheep and poultry to a recombinant vaccinia virus expressing a swine influenza haemagglutinin.

Groups of cattle, sheep and poultry were inoculated with a recombinant vaccinia virus expressing the haemagglutinin of the swine influenza virus A/NJ/11/76. No adverse clinical responses were recorded and none of the animals developed a viraemia when inoculated with the recombinant or wild-type vaccinia virus. Recombinant virus reisolated from lesions in cattle was stable, maintaining its thymidine kinase negative phenotype and ability to express the swine influenza haemagglutinin. Antibodies to the influenza haemagglutinin were detected in cattle, sheep and poultry inoculated with the recombinant virus. While no animals inoculated with wild-type virus developed these antibodies, there was no detectable spread of either recombinant or wild-type virus from the inoculation sites or to in-contact uninoculated animals. The results indicate that recombinant vaccinia viruses can induce immune responses in cattle, sheep and poultry demonstrating their potential as vaccine vectors in a variety of important veterinary species.

Animals↗
PubMed1985

Bluetongue, epizootic haemorrhagic disease of deer and related viruses: current situation in Australia.

Since 1975 3 serotypes of bluetongue (BT) virus (BTV) have been identified in Australia: BTV1 (CSIRO156), BTV20 (CSIRO19) and BTV21. At present 2 further BT viruses (DPP90 and DPP192) have been isolated from the blood of healthy cattle in the Northern Territory (NT) and are undergoing identification. There is serological evidence for BTV15 infection in Western Australia (WA) and the NT, and a background level of serological activity to BTV serotypes 1 to 17. In addition, over 50 isolations of epizootic hemorrhagic disease of deer (EHD) viruses (EHDV) have been made and can be divided into 5 main serotypes, CSIRO157, CSIRO439, CSIRO753, CSIRO775 and DPP59. All 5 serotypes occur within the ecological range of Culicoides brevitarsis, however, as for BTV, the high prevalence of antibodies in cattle in the Kimberley region of WA and the top end of the NT suggests other vectors may also be responsible. CSIRO439 has been shown to be closely related serologically to Ibaraki virus while the other EHD viruses were distinct from Ibaraki and from each other. The complex serological relationships between BTV, EHDV and Palyam virus groups are currently being examined using serological and biochemical techniques. It is often difficult to determine the differences between BTV and EHDV serogroup members. Antibodies to both BTV and EHDV have been found in cattle, buffaloes and deer but there has been no evidence of clinical disease in any of these species or in sheep under field conditions in Australia.

Animals↗
PubMed1985

Problems in the interpretation of diagnostic tests due to cross-reactions between orbiviruses and broad serological responses in animals.

Tests presently used for the diagnosis of infections by bluetongue virus (BTV) or related orbiviruses are based on the use of 2 types of serological reactions. Those that are considered group-reactive tests are the agar gel diffusion precipitin (AGDP), complement-fixation (CF) and fluorescent antibody tests and those that are considered type-specific are a wide variety of virus neutralization tests (50% and 80% plaque reduction, plaque inhibition and microtiter neutralization) and cross-protection tests. These tests suffer from problems of standardization between laboratories and of specificity. Group-reactive tests (AGDP and CF) for the BTV serogroup also detect cross-reactions with viruses in the epizootic hemorrhagic disease virus (EHDV), Eubenangee (EUB) and Palyam (PAL) serogroups, with the EHDV cross-reactions being of particular concern. Further, multiple infections of cattle with PAL serogroup members can produce antibodies which will react to BTV and EHDV serogroup antigens in serological tests. Multiple infections of animals with related viruses can produce antibodies which will cross-react with orbiviruses in type-specific, virus neutralization tests to a virus which the animal has not previously been exposed. These observations stress the need to evaluate the tests at present being used, to assess the risks of cross-reactions between related orbiviruses and to develop new tests of defined specificity.

Animals↗
PubMed1977

Incidence of Tritrichomonas foetus in young replacement bulls following introduction into an infected herd.

Three hundred 8-year-old Shorthorn and Santa Gertrudis bulls, with a 47% incidence of Tritrichomonas foetus infection in the 30 surveyed, were removed from a herd of approximately 6000 cows and replaced by 325 two-year-old Brahman bulls. A sample of 50 of the replacement bulls was examined at introduction and found to be uninfected. After 2 years, the incidence of infection in a sample of 80 of the replacement bulls was 4%. The results suggests that a major reduction in incidence of infection in extensively managed herds might be achieved by the exclusive use of young bulls for mating.

Age Factors↗
PubMed1977

Studies on the transmission of Tritrichomonas foetus.

Although 2 experiments showed that non-infected bulls can passively transmit Tritrichomonas foestus from infected to non-infected cows during mating, the rates of transmission were low. The results of the second experiment, in which time intervals between services were recorded, suggested that T. foetus was most likely to become established in previously non-infected cows when the interval was less than 20 minutes. Application of 2 X 10(6) active cells of T. foetus to the vulva failed to cause genital infection in 10 cows.

Animals↗
PubMed1977

A dual vaccine for the immunisation of cattle against vibriosis.

Single subcutaneous injections of a mineral oil adjuvant vaccine containing 20 mg dry weight of Campylobacter fetus subsp fetus biotype venerealis cells and 20 mg dry weight of C. fetus subsp fetus biotype intermedius cells per 5 mil dose protected 2- and 3-year-old heifers and 3- and 4-year-old cows against genital infection with either organism.

Animals↗