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Biomedical subjects

M P Ward

Publications and source records attributed to M P Ward.

At least 37 records · Page 2Linked to original sources
PubMed1997

Evaluation of a composite method for counting helminth eggs in cattle faeces.

Data from a cattle helminth monitoring service operated in Queensland, Australia were used to evaluate a composite faecal egg counting method using the modified McMaster technique. The composite method was compared with the standard method of performing egg counts on each individual faecal sample per submission. No significant (P > 0.05) difference was detected in the egg count results provided by the composite and standard methods. An excellent level of agreement (kappa statistic = 0.86) between the two methods was also found when count results were categorised. We consider the composite counting method to be a valid alternative to performing counts on all individual faecal samples submitted from cattle herds to diagnostic laboratories for parasitological examination. The use of composite method represents significant savings in time, labour and the cost of parasitological services offered by laboratories.

Animals↗
PubMed1997

Simulation analysis of the effect of herd immunity and age structure on infection of a cattle herd with bluetongue viruses in Queensland, Australia.

A state-transition model based on Leslie matrix formulation was used to investigate the effects of herd immunity and age structure on the infection of a simulated cattle herd with bluetongue viruses under Australian climatic conditions. Increasing duration of immunity decreased the prevalence of infection. A duration of immunity of 33 months was consistent with prevalence estimates made from previous serological studies of bluetongue virus. Herd prevalence displayed slowly dampening cyclical variation over time (most pronounced when a short duration of immunity was simulated). Increasing calving and mortality risk rates in the simulated herd increased prevalence, whereas increasing age at first calving decreased prevalence. Manipulation of calving rates had the greatest effect on the predicted prevalence of infection in the herd. Simulation of a number of herd-management scenarios suggested that management systems in which cattle are bred early and where high calving rates are achieved are likely to contribute to high levels of infection with bluetongue viruses. Results confirm the importance of management factors in influencing the prevalence of infectious diseases in animal populations.

Aging↗
PubMed1997

Association between risk of seroconversion of sentinel cattle to bluetongue viruses and Culicoides species (Diptera: Ceratopogonidae) in Queensland, Australia.

The association between risk of seroconversion of sentinel cattle to bluetongue viruses and the number of Culicoides brevitarsis Kieffer and C. wadai Kitaoka caught by light traps was investigated using survival analysis. Eight sentinel herds that seroconverted to bluetongue viruses between 1990 and 1994, and for which insect-trapping data were available, were selected for inclusion in the study. These herds were located at six sites along the eastern coast of Queensland, Australia, from approximately latitude 10 degrees South to 25 degrees South. C. brevitarsis was detected at all locations where sentinel herds were maintained, whereas C. wadai was detected at only two locations in northern Queensland where four sentinel herds were maintained during the study period. The mean number of C. brevitarsis and C. wadai caught per month was 230 and 21, respectively. A significant (P = 0.05) positive association was found between the risk of seroconversion of sentinel cattle to bluetongue viruses and the number of C. wadai caught in the same month.

Animals↗
PubMed1996

Climatic factors associated with the infection of herds of cattle with bluetongue viruses.

The incidence of bluetongue virus infection of 15 cattle herds in Queensland, Australia, was determined by a serum neutralization test. The maximum temperature (degree C), minimum temperature (degree C) and rainfall (mm) data were obtained from the meteorological recording stations closest to each herd. Using unweighted least-squares regression analysis, the best statistical model explaining the most variability in the herd incidence rate included the ratio between the maximum and minimum temperature recorded at both 1 month and 6 months preceding seroconversion, and rainfall recorded at both 2 months and 6 months preceding seroconversion. More than 90% of the variability in the incidence of bluetongue virus infection in the herds was explained by the model, a considerable improvement on previous models that used prevalence data. The prospective nature of the study also supports a strong causal relationship between climatic factors and the occurrence of infection in cattle herds.

Analysis of Variance↗
PubMed1996

Evaluation of a competitive enzyme-linked immunosorbent assay to detect infection of cattle in sentinel herds in Queensland, Australia with bluetongue viruses.

A competitive enzyme-linked immunosorbent assay (ELISA) was used to detect serogroup specific antibodies to bluetongue viruses. This test is commercially available and was evaluated with serially collected sera from 10 sentinel herds of cattle maintained in Queensland, Australia during 1994. Determination of an infection during the period of observation was based on the development of a serum neutralisation (SN) test titre > or = 1:8 to any one of 8 bluetongue virus serotypes known to exist in Australia. Using the inhibition value of 40% recommended by the manufacturer to classify cattle as exposed to bluetongue viruses, the ELISA was highly sensitive (100%; 95% confidence interval, 77.9-100%) and moderately specific (86.4%; 95% CI, 77.0-93.0%), relative to the SN test. An inhibition value of 70% maximised both sensitivity (100%, lower 95% CI, 77.9%) and specificity (93.2%, 95% CI, 85.2-98.0%) of the ELISA. The chance (posttest probability) of an animal from which a serum sample had an inhibition value > or = 70 % in the ELISA developing an SN test titre > or = 1:8 was 93.6% (95% CI, 86.4-97.9%). Investigations of the temporal development of ELISA and SN test reactions, showed that the ELISA detected exposure to bluetongue viruses significantly (P = 0.0156) earlier than the SN test. The bluetongue virus ELISA is a useful test in surveillance programs. False positive assay results make it inappropriate for monitoring and diagnosis, unless it is used in conjunction with the SN test.

Animals↗
PubMed1996

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland.

OBJECTIVE: To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses. DESIGN: A sentinel herd study. SAMPLE POPULATION: Sixty-nine sentinel herds at 30 locations. PROCEDURE: Spatial clustering of seroconversion to bluetongue viruses was investigated during the period from 1990 to 1994. RESULTS: Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland. CONCLUSION: Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.

Animals↗
PubMed1995

The Nir1 locus in barley is tightly linked to the nitrite reductase apoprotein gene Nii.

pBNiR1, a cDNA clone encoding part of the barley nitrite reductase apoprotein, was isolated from a barley (cv. Maris Mink) leaf cDNA library using the 1.85 kb insert of the maize nitrite reductase cDNA clone pCIB808 as a heterologous probe. The cDNA insert of pBNiR1 is 503 bp in length. The nucleotide coding sequence could be aligned with the 3' end of other higher plant nitrite reductase apoprotein cDNA sequences but diverges in the 3' untranslated region. The whole-plant barley mutant STA3999, previously isolated from the cultivar Tweed, accumulates nitrite after nitrate treatment in the light, has very much lowered levels of nitrite reductase activity and lacks detectable nitrite reductase cross-reacting material due to a recessive mutation in a single nuclear gene which we have designated Nir1. STA3999 has the characteristics expected of a nitrite reductase apoprotein gene mutant. Here we have used pB-NiR1 in RFLP analysis to determine whether the mutation carried by STA3999 is linked to the nitrite reductase apoprotein gene locus Nii. An RFLP was identified between the wild-type barley cultivars Tweed (major hybridising band of 11.5 kb) and Golden Promise (major hybridising band of 7.5 kb) when DraI-digested DNA was probed with the insert from the partial barley nitrite reductase cDNA clone, pBNiR1. DraI-digested DNA from the mutant STA3999 also exhibited a major hybridising band of 11.5 kb after hybridisation with the insert from pBNiR1.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

Evaluation of an agar gel immunodiffusion test to detect infection of cattle with bluetongue viruses in Queensland, Australia.

An agar gel immunodiffusion (AGID) test to detect group-specific antibodies to infection of cattle by bluetongue viruses was evaluated using field collected sera in Queensland, Australia. The AGID test was compared to the serum neutralisation (SN) test used to detect serotype-specific bluetongue virus antibodies. The AGID test was found to be highly sensitive (95% confidence interval, 80.7-100%) but to have moderate specificity (95% confidence interval, 59.3-79.6%), relative to the SN test. The correlation between AGID and SN test results was 0.41 (P < 0.001). Using likelihood ratio estimates the chance (posttest probability) of an AGID test positive serum sample being positive (titre > or = 1:20) in the SN test was estimated to be 87% and 90% for 2+ and 3+ AGID test reactions, respectively. A serum sample was estimated to have a probability of 40% of being positive in the SN test if it gave a 1+ reaction in the AGID test. Results suggest that the AGID test should ideally be used as a screening test in serological surveys and surveillance programs. If the test is to be used for identification of individually infected cattle, a cutoff point of > or = 2+ should be employed.

Animals↗
PubMed1995

Infection of cattle with bluetongue viruses in Queensland, Australia: results of a sentinel herd study, 1990-1992.

Between 1990 and 1992, 47 sentinel herds of 10-20 cattle each were established throughout Queensland, Australia to monitor bluetongue virus infection. Sixteen herds at 12 locations seroconverted to bluetongue viruses during the study. Herd incidence rates ranged from 0.0 to 3.45 seroconversions per cattle-year at risk. The mean incidence rate was 0.29 seroconversions per cattle-year at risk (95% confidence interval 0.23-0.36), and the median incidence rate was 0.32 seroconversions per cattle-year at risk (95% CI 0.0-0.54). Only seroconversions to bluetongue virus serotypes 1 and/or 21 were detected in the study; no evidence was found of infection with other serotyped previously isolated in Australia (3, 9, 15, 16, 20, 23). Seroconversion to serotype 1 occurred more frequently than seroconversion to serotype 21. Seroconversion generally occurred between April and July, being most common in May, but varied considerably within each of the 3 years of the study. This study confirmed the presence of only serotypes 1 and 21 in Queensland and demonstrated the sporadic and restricted nature of bluetongue virus infection in the Queensland cattle herd.

Animals↗
PubMed1995

Infection of cattle in Queensland with bluetongue viruses: 1. Prevalence of antibodies.

A survey of nearly 20,000 cattle in Queensland was conducted to describe the prevalence and distribution of infection by serotypes of bluetongue virus. The overall prevalence of serum antibodies to one or more bluetongue viruses was 8.7% (95% confidence interval 8.3 to 9.1). Sera from cattle contained neutralising activity against 2 serotypes, 1 and 21. No evidence was found of infection with other serotypes previously isolated in Australia. The overall prevalence of serotype 1 antibodies was 7.7% (95% CI 7.3 to 8.0) and the prevalence of serotype 21 antibodies was 3.3% (95% CI 3.1 to 3.6). The prevalence of serotype 1 antibodies was significantly (P < 0.05) higher than that of serotype 21 in every region of the State, except in the central highlands and south-west Queensland. Overall, 3 significantly (P < 0.05) different zones of prevalence were found: high prevalence (> 20%) in far north Queensland, moderate (5 to 20%) in north-west, northern and southern coastal Queensland, and low (< 5%) in the central highlands, Darling Downs and south-west Queensland.

Animals↗
PubMed1995

Infection of cattle in Queensland with bluetongue viruses: II. Distribution of antibodies.

A survey of the distribution of serum antibodies to bluetongue viruses in Queensland cattle herds was conducted in 1989. A total of 410 herds were selected in which sera from 20 or more cattle had been tested with the agar gel immunodiffusion (AGID) test. Estimates of prevalence were standardised for age of cattle and adjusted using results from serum neutralisation (SN) tests. Spatial statistical methods were used to investigate the distribution of these selected herds with respect to the prevalence of serum antibodies to bluetongue viruses. The mean herd prevalence was 5.2% (95% confidence interval 4.5 to 5.9) and the median herd prevalence was 3.5% (95% CI 2.8 to 4.2). Prevalence was highest in far north Queensland (17.3%) and lowest in south-west Queensland (0.3%). Significant (P < 0.01) clustering of selected herds with respect to prevalence of serum antibodies was found. Herds with prevalence of serum antibodies to bluetongue viruses above the overall mean herd prevalence were significantly (P < 0.05) clustered in the north-west, far north and northern and southern coastal regions of Queensland. Clustering within the north-west and southern coastal regions of Queensland was more pronounced than the clustering detected in the northern coastal and far north regions.

Animals↗
PubMed1995

SOK2 may regulate cyclic AMP-dependent protein kinase-stimulated growth and pseudohyphal development by repressing transcription.

Yeast cyclic AMP (cAMP)-dependent protein kinase (PKA) activity is essential for growth and cell cycle progression. Dependence on PKA function can be partially relieved by overexpression of a gene, SOK2, whose product has significant homology with several fungal transcription factors (StuA from Aspergillus nidulans and Phd1 from Saccharomyces cerevisiae) that are associated with cellular differentiation and development. Deletion of SOK2 is not lethal but exacerbates the growth defect of strains compromised for PKA activity. Alterations in Sok2 protein production also affect the expression of genes involved in several other PKA-regulated processes, including glycogen accumulation (GAC1) and heat shock resistance (SSA3). These results suggest SOK2 plays a general regulatory role in the PKA signal transduction pathway. Expression of the PKA catalytic subunit genes is unaltered by deletion or overexpression of SOK2. Because homozygous sok2/sok2 diploid strains form pseudohyphae at an accelerated rate, the Sok2 protein may inhibit the switch from unicellular to filamentous growth, a process that is dependent on cAMP. Thus, the product of SOK2 may act downstream of PKA to regulate the expression of genes important in growth and development.

Amino Acid Sequence↗
PubMed1994

Climatic factors associated with the prevalence of bluetongue virus infection of cattle herds in Queensland, Australia.

The prevalence of bluetongue virus in 410 cattle herds in Queensland, Australia, was estimated by using the bluetongue virus agar gel immunodiffusion test, and 18 climatic variables were estimated for the location of each herd. Temperature and rainfall were the factors most closely associated with the prevalence of bluetongue virus in the herds, and the simplest relationship which explained the most variability in the prevalence included the average daily maximum temperature and the average annual rainfall. This relationship accounted for nearly 40 per cent of the variability in herd prevalence. The generally poor association between climatic factors and herd prevalence indicates that other factors need to be included in any model of the epidemiology of bluetongue virus.

Animals↗