Sergio J Johnson

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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(More)
Mueller matrix polarimeters (MMPs) are designed to probe the polarization properties of optical scattering processes. When using a MMP for a detection, discrimination, classification, or identification task, a user considers certain elements of the Mueller matrix. The usual way of performing this task is to measure the full Mueller matrix and discard the(More)
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(More)
AIMS This was a pilot study of the use of a clinical pharmacist as a therapeutics adviser (academic detailer) to modify antibiotic prescribing by general practitioners. METHODS Following a visit by the adviser (March-May), 112 general practitioners were recruited and randomised to control or active groups. A panel of experts prepared a best practice chart(More)
Trials were conducted in three regions of Australia to investigate the potential for improvised shelters and chemical treatments to reduce feeding by Culicoides on cattle and thereby minimise the risk of bluetongue transmission during transport of cattle to ports. Various designs and combinations of roofs and walls were placed around penned cattle. Chemical(More)
A cell culture attenuated Australian bluetongue virus serotype 23 (BLU23) prototype vaccine was assessed for its effects on pregnant Merino sheep. Seventy-six ewes were vaccinated at 5 different stages of gestation, and the failure to lamb at term was as follows: 35 to 43 days of gestation, 20/36 (56%); 57 to 64 days of gestation, 3/10 (30%); 81 to 88 days(More)
Field collected Culicoides brevitarsis Kieffer and C. wadai Kitaoka were fed on sheep that had been artificially infected with a field-isolate of either bluetongue virus serotype 3 (BLU3), BLU9, BLU16, or BLU23. Feeding rates averaged 11.9% but were variable. Survival of midges during incubation tended to be enhanced by the addition of antibiotics and(More)
Finely ground Corchorus olitorius seed was administered as a daily drench to 1 pig at 100mg/kg body weight and as a single drench to 2 pigs at 500 mg/kg body weight. The latter 2 died within 48 hours, and the former was killed on the 7th day as it approached a moribund state. Clinical signs observed were anorexia, vomiting and dysentery. Autopsy revealed(More)
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,(More)