PubMed Health⌕ Search

Biomedical subjects

R A Hawkes

Publications and source records attributed to R A Hawkes.

At least 19 recordsLinked to original sources
PubMed2002

Studies on the epidemiology of bluetongue virus in China.

Sentinel herds of large ruminants were established at five centres in Yunnan Province, Peoples Republic of China, between 1995 and 1997. The application of a sensitive antigen capture ELISA to facilitate virus isolation procedures led to the isolation of 108 strains of bluetongue (BLU) virus. Serotypes isolated included types 1, 2, 3, 4, 9, 11, 12, 15, 16, 21 and 23. Virus transmission occurred over a period of 1-3 months at each of the four positive sites, giving an overall BLU virus transmission period for the province of 5 months, from early June to early November. The greatest level of transmission took place in July and August. The duration of viraemia in individual animals varied from 1 to 7 weeks, with a mean calculated for each serotype between 6 and 20 days. The study represents the first detailed investigation of the epidemiology of BLU in China utilizing sentinel herds.

Animals↗
PubMed2000

Laboratory and field studies of an antigen capture ELISA for bluetongue virus.

An improved bluetongue antigen capture ELISA (BTACE) technique was evaluated for its ability to detect the full range of 24 bluetongue (BLU) serotypes. The BTACE detected all 24 serotypes in cell culture fluids, including eight serotypes where the representative strains originated from both Australia and also from the South African reference collection. The amount of infectious virus required to obtain a positive BTACE result varied between 100-1000 TCID50. This was approximately 10-fold more sensitive than the antigen capture test described previously (Hosseini, M., Hawkes, R.A., Kirkland, P.D., Dixon, R., 1998. J. Virol. Methods 75, 39-46.). The BTACE method was compared with conventional passage in cell culture to detect the presence of virus in the tissues of embryonated chicken eggs (ECEs) which had been inoculated intravenously with the blood of sheep and cattle infected experimentally with the eight Australian serotypes of BLU (1, 3, 9, 15, 16, 20, 21, and 23). The BTACE method was at least as sensitive as the conventional cell culture detecting virus in ECEs, obviating the need for prolonged cell culture passage to detect the virus. A comparison of the amount of antigen detected in different embryo tissues indicated that liver homogenates gave the highest positive to negative ratios in the BTACE and were selected as the specimen of choice. In studies of sheep infected with all 24 South African reference BLU serotypes this new BTACE was able to detect viraemia with all serotypes. Finally, the BTACE was validated in surveillance programs for BLU in both New South Wales, Australia and in Yunnan Province, People's Republic of China. Blood samples from sentinel cattle were inoculated into ECEs. Homogenised ECE livers were tested by BTACE and those positive were passaged subsequently in cell culture for virus isolation and identification. This protocol led to the efficient isolation of field isolates of many serotypes. The high sensitivity and broad reactivity of the method indicates that it should be valuable for BLU diagnosis and surveillance programs.

Animals↗
PubMed1998

Rapid screening of embryonated chicken eggs for bluetongue virus infection with an antigen capture enzyme linked immunosorbent assay.

The sensitivity and specificity of an antigen capture ELISA have been compared with virus isolation in cell culture. Bluetongue virus (BLU) (serotype 23) from the blood of a sheep was titrated by inoculating embryonated chicken eggs (ECEs) and detecting viral antigen in chicken embryo livers using an antigen capture enzyme linked immunosorbent assay (ELISA) (Stanislawek et al., 1996. Detection by ELISA of bluetongue antigen directly in the blood of experimentally infected sheep. Vet. Microbiol. 52, 1-12). Five days after inoculation of ECEs with lysed red blood cells from the infected sheep the embryo livers were harvested and homogenised. The supernatant from the homogenate was used in the antigen capture ELISA to determine which livers were infected and the virus titre calculated as CEID50/ml packed red blood cells. These results were compared with a standard cell culture isolation protocol which passaged the liver homogenate supernatant through Aedes albopictus cells and up to three passages in BHK21 cells. The antigen capture ELISA showed 100% sensitivity and specificity with no false negatives or false positives when compared to cell culture isolation of the virus. The major advantage of the combination of ECE inoculation and antigen capture ELISA is the reduction in the time to less than 7 days from a maximum of 35 days for the ECE/cell culture system. The procedure is easy to undertake, cost effective and does not require expensive specialist cell culture facilities.

Aedes↗
PubMed1995

Transferring the costs of expensive treatments from secondary to primary care.

General practitioners, especially fundholders, are becoming increasingly concerned about being asked to prescribe treatments for their patients that are outside their therapeutic experience. They are concerned about the clinical responsibility for such prescribing and the effects on their budgets. In some specialties transferring the costs of expensive treatments from secondary to primary care (cost shifting) has become partly institutionalised because of the separate sources of funding for drugs prescribed in the two sectors. With increased efforts to control the rising costs of the drugs budget and the emergence of new expensive treatments, cost shifting will be a challenge to clinicians and purchasers as they strive for rational, cost effective prescribing. A review of the funding mechanisms for drugs prescribing and of the relation between the licensing process and the decision to support the use of a treatment in primary or secondary care is needed.

Budgets↗
PubMed1993

Arbovirus infections of humans in high-risk areas of south-eastern Australia: a continuing study.

OBJECTIVES: To determine the current immune status of high-risk populations of New South Wales and Victoria to the arboviral pathogens, Murray Valley encephalitis (MVE) and Kunjin (KUN) viruses, which are associated with Australian encephalitis (AE), and Ross River (RR) and Kokobera (KOK) viruses which are associated with polyarthritis. Further, to estimate seroconversion rates to these viruses in high-risk populations over the 10-year period 1981-1991. DESIGN AND STUDY POPULATION: Blood was taken from 2873 permanent residents, children and adults from previously identified high-risk areas in western NSW and northern Victoria. Samples were tested by the haemagglutination-inhibition (HI) test for antibodies to the four viruses. All sera were also tested for MVE and KUN antibodies by the more specific neutralisation test (NT). Ninety-five of the subjects had been seronegative when sampled 10 years previously. RESULTS: Age standardised prevalence rates for flavivirus HI antibodies (MVE, KUN, KOK) ranged from 66% (Bourke) to 15% (Forbes), and were similar to those observed 10 years previously. However, specific NT antibodies to MVE and KUN were uncommon in all districts except Bourke, indicating a very high level of susceptibility to Australian encephalitis, should a fresh epidemic occur. Whereas KUN virus seems enzootic in NSW and Victoria, MVE did not appear to have been present since the last outbreak in 1974, even in Bourke. Flavivirus antibody rates (as detected by the broadly reactive HI test) greatly exceeded those specifically attributable to MVE and KUN (NT test) or KOK, leading to the speculation that unidentified flaviviruses are responsible for most human infections. Ross River virus antibody prevalence rates exceeded those of flaviviruses in all districts, ranging from 72% (Bourke) to 25% (Cohuna), and were uniformly higher than those observed in 1981. Ten-year seroconversion rates in seronegative panels were 8.5% for flaviviruses and 24.2% for RR virus, and are broadly consistent with the cross-sectional study. CONCLUSIONS: Although flavivirus and alphavirus infections have occurred at a "steady rate"in western NSW and northern Victoria, there is a general lack of immunity to the agents of Australian encephalitis in all centres except Bourke. This needs to be considered in public health policy in these areas.

Adolescent↗
PubMed1993

Helicobacter pylori infection within families.

Although H. pylori is now well established as the aetiological agent of acute or chronic gastritis and a predisposing factor in peptic ulceration knowledge regarding the transmission of this organism is unclear. The aim of this study was to examine the prevalence of H. pylori infection in the family members of index children infected with this organism and to examine the role of ethnic background and the relationship of hepatitis A infection to H. pylori infection. The H. pylori status of three groups of subjects, the family members of 21 children shown by endoscopical and histological examination to be infected with H. pylori, the family members of 17 children who had been the index case in a hepatitis study and a control group of Australian blood donors and children were examined using an IgG ELISA. The results of this study showed an increased prevalence of H. pylori infection to exist in the family members of index children infected with H. pylori compared with the family members of children not infected with H. pylori and an age matched blood donor control group. This increased prevalence of H. pylori infection was not dependent on ethnic background and appeared to be unrelated to the hepatitis A status of subjects. These results strongly support the view that transmission of H. pylori is person to person and that transmission may not be the faecal oral route.

Adolescent↗
PubMed1991

Fundholding in general practice and financial risk.

OBJECTIVE: To estimate the financial effect of random yearly variations in need for services on fundholding practices with various list sizes. DESIGN: A simulation model was derived using historical data on general practitioner referrals for the 113 surgical procedures covered by the general practitioner fund, combined with data on the hospital prices for those procedures. PATIENTS: Resident population of Central Birmingham Health Authority. MAIN OUTCOME MEASURES: Expected expenditure on the relevant surgical procedures for the whole district and for practices with list sizes of 9000, 12,000, 15,000, 18,000, 21,000, or 24,000 for each of 100 simulated years. RESULTS: By using average hospital prices for the West Midlands region the mean (SD) annual expenditure for the 179,400 residents was 4,832,471 pounds (87,149 pounds); the random variation between the 5th and 95th most expensive years was 5.7% of the mean cost. For a practice with a list size of 9000 the values were 244,891 pounds (18,349 pounds), with a variation of 27.5%. With a list size of 24,000 the values were 652,762 pounds (32,512 pounds), with a variation of 15.3%. CONCLUSIONS: Random variations in need for inpatient services will have a significant financial impact on the practice fund. The problem will be particularly great for smaller practices. Additional measures are required to ensure that the scheme is not undermined and that the potential benefits are secured.

Budgets↗
PubMed1990

Defined epitope blocking with Murray Valley encephalitis virus and monoclonal antibodies: laboratory and field studies.

In an attempt to develop a specific serological test for Murray Valley encephalitis (MVE) virus antibodies, a panel of MVE monoclonal antibodies was utilised in defined-epitope blocking ELISA tests. In sera of mice immunised singly and in combinations of MVE, Alfuy (ALF), and Kunjin (KUN) viruses, blocking patterns usually distinguished MVE infections from those of the other flaviviruses. When blocking tests with selected MAbs were applied to 468 flavivirus antibody positive sera collected from human subjects throughout New South Wales, sera with blocking patterns consistent with previous MVE infection were found in 18 subjects. All were long-term residents of areas previously frequented by MVE, and all were of an age to have been exposed to the virus in past epidemics. No such sera were found in subjects living in coastal areas of NSW where MVE has never been reported.

Animals↗
PubMed1990

Arbovirus infection in humans in NSW: seroprevalence and pathogenicity of certain Australian bunyaviruses.

A sero epidemiological study was carried out on human sera from all regions of New South Wales for the presence of antibodies to nine bunyaviruses viz Aino, Akabane, Belmont, Gan Gan, Kowanyama, mapputta, Peaton, Tinaroo, Trubanaman and the orbivirus Corriparta. Neutralising antibodies were found in titres up to 1280 to Gan Gan and to 640 to Trubanaman viruses, prevalences 4.7% and 1.4% respectively. Neutralisation titres up to 40 were found to Belmont, Aino, Peaton and Corriparta viruses but the significance of these is uncertain since they may represent either non-specific inhibitors or cross reacting antibodies to related but currently unknown viruses. No antibodies were found to Akabane, Kowanyama, Mapputta or Tinaroo viruses in New South Wales sera. Gan Gan virus appeared to be pathogenic for man being associated with an acute epidemic polyarthritic like illness. Trubanaman virus is suspected of being pathogenic. This is the first report of the pathogenicity of these Australian bunyaviruses.

Adolescent↗
PubMed1989

Japanese encephalitis after a two-week holiday in Bali.

Japanese encephalitis is described in a 10-year-old girl after a short holiday in Bali. Four days after returning to Australia the patient presented with a high fever, stupor and rapidly-developing focal neurological signs. Recovery occurred gradually over a period of three months and she has returned to school. Japanese encephalitis viral infection was confirmed by a marked rise in specific haemagglutination-inhibition antibodies and the presence of immunoglobulin M antibodies to the flavivirus group. It is important to be aware of the possibility of arboviral infection in patients with encephalitis. In view of the recent outbreaks of Japanese encephalitis in Asia, travellers to the region should be warned to protect themselves from mosquito-bites.

Acute Disease↗
PubMed1989

Synthetic peptides derived from the deduced amino acid sequence of the E-glycoprotein of Murray Valley encephalitis virus elicit antiviral antibody.

We used computer analysis to study hydrophilicity, homology, surface accessibility, molecular flexibility, and secondary structure of the deduced amino acid sequence of the flavivirus envelope (E)-glycoprotein. Using the results, we modified the E-glycoprotein antigenic structure proposed by Nowak and Wengler (1987, Virology, 156, 127-137). Our model predicts considerable overlaps in the previously defined domains. We have prepared 11 synthetic peptides from the deduced amino acid sequence of the E-glycoprotein of Murray Valley encephalitis (MVE) virus and analyzed their immunogenicity. Peptides derived from the redefined R1 and R2 domains elicit antiviral antibody. Nine of these peptides are recognized by polyclonal antiviral antibodies; however, none are consistently recognized by monoclonal antibodies. Peptides derived from the R1 domain demonstrate MVE virus specificity, and 1 peptide elicited low-level virus neutralizing antibody. Spatial overlap of the domains was defined by competitive binding assays between antipeptide antisera and radioactive monoclonal antibodies. These results indicate that synthetic peptides aid in defining flavivirus antigenic structure, and may serve as possible type-specific diagnostic reagents.

Amino Acid Sequence↗
PubMed1988

Illness caused by a Barmah Forest-like virus in New South Wales.

Barmah Forest virus, a recently-discovered arbovirus which belongs to the alphavirus genus of the family Togaviridae, has been shown to cause infections in humans in New South Wales. The present report documents three patients in whom Barmah Forest viral infection appears to have resulted in illness. Barmah Forest virus or a closely-related alphavirus may, as are several other alphaviruses, be pathogenic.

Adult↗
PubMed1988

Antigenic structure of the Murray Valley encephalitis virus E glycoprotein.

To complement our battery of St Louis encephalitis (SLE) virus monoclonal antibodies (MAbs), we isolated and characterized MAbs reactive with another member of the SLE virus serocomplex, Murray Valley encephalitis (MVE) virus. From 40 fusion products, we isolated 10 stable hybridomas. The combination of SLE and MVE virus MAbs defined eight epitopes on the MVE envelope (E) glycoprotein. Six of these epitopes (E-1a, E-1c, E-1d, E-3, E-4a, E-4b) were identical to those previously demonstrated on SLE virus. Two new epitopes (E-5 and E-6) were also identified. As with SLE virus, the MVE E-1c epitope elicited the most potent virus-neutralizing and protective MAb. Unlike SLE virus, however, one of the cross-reactive epitopes (E-5) elicited neutralizing antibody and protected animals from MVE virus challenge. These results indicate that, while the antigenic domains on viruses within the SLE virus serocomplex are quite similar, epitopes involved in virus neutralization or protection from virus challenge may vary and can be topologically distinct.

Antibodies, Monoclonal↗
PubMed1988

Stability of St. Louis encephalitis viral antigen detected by enzyme immunoassay in infected mosquitoes.

The use of enzyme immunoassay to detect St. Louis encephalitis (SLE) viral antigen in vector mosquitoes enhances the effectiveness of surveillance because infected mosquitoes can be identified more rapidly than with conventional virus isolation systems and because it is a simple and accessible procedure. Infectivity among mosquitoes experimentally infected with SLE virus was lost within 24 h after the mosquitoes were stored at 27 degrees C and 80% relative humidity; however, viral antigen remained stable under these conditions and could be detected by enzyme immunoassay 2 weeks later. Desiccation further extended the period during which antigen could be detected to 6 weeks. Absorbances were higher in infected mosquitoes stored at 27 degrees C than in mosquitoes frozen continuously. Absorbances in infected mosquitoes also increased after repeated freezing and thawing and sonication. Both phenomena may be related to the release of antigen from decaying or disrupted cells. The relative stability of SLE viral antigen at ambient temperatures lends flexibility to schemes which use direct antigen detection to identify vectors. Surveillance systems can be designed without regard to collecting living mosquitoes, and a cold chain in unnecessary to preserve specimens, thus reducing the cost of surveillance and expanding the geographic areas to which it is accessible.

Animals↗
PubMed1987

Barmah Forest virus infections in humans in New South Wales.

Antibodies to Barmah Forest virus, a member of the alphavirus group, which was first isolated in 1974, have been found to be widespread in humans in New South Wales. Antibody studies showed a higher prevalence in the north coastal zones of the State, and lower rates in individuals who were living in all other biophysical zones. Antibody rates were significantly higher in male than in female subjects. The pathogenicity of the Barmah Forest virus is at present not known.

Adolescent↗
PubMed1987

Characterization of gp 50, a major glycoprotein present in rat brain synaptic membranes, with a monoclonal antibody.

Several cell lines secreting monoclonal antibodies (Mabs) against a major forebrain synaptic membrane (SM) glycoprotein, gp 50, have been raised. Western blots show that the Mabs react with a polypeptide doublet of Mrs 49 and 45 kDa. These polypeptides exist solely in a concanavalin A (Con A) binding form. Removal of the Con A receptors by digestion with endo-beta-N-acetylglucosaminidase H (endo H) lowers the Mrs of the glycoprotein doublet to 36.5 and 34 kDa. Western blots of 2D polyacrylamide gels indicate that gp 50 exists in several isoforms. Solid phase radioimmunoassay (RIA) and Western blots of brain subcellular fractions show the antigenic material to be concentrated in the SM fraction, but to be present in much lower amounts in synaptic junctions and postsynaptic densities. Gp 50 appears to be brain specific. Regional distribution studies show that it is present in all brain regions but is two-fold concentrated in cerebellum, brainstem and midbrain compared to forebrain. Immunocytochemical studies of several brain regions show that gp 50-like immunoreactivity is neuron specific and is concentrated in selected neuronal species, particularly granule cells. In both cerebellar and hippocampal granule cells gp 50-like immunoreactivity is localized in the perikarya and primary dendrites. Though immunocytochemistry did not show staining of synaptic regions this may be due to masking of the reactive epitope. The results are discussed in terms of the molecular properties of gp 50 and its subcellular localization in brain tissue.

Animals↗
PubMed1986

Illness caused by a Kokobera-like virus in south-eastern Australia.

Three patients who lived in south-eastern Australia and who suffered acute polyarticular illnesses in the summer months of 1983-1984 and 1984-1985 are described. Two patients lived in the southwestern plains of New South Wales and one in Bairnsdale in eastern Victoria. Serological studies implicated Kokobera virus, a flavivirus, as the likely causative agent. This would appear to be the first report to indicate the pathogenicity of Kokobera virus.

Adult↗