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Biomedical subjects

J W Browning

Publications and source records attributed to J W Browning.

11 recordsLinked to original sources
PubMed1997

Strain differentiation of isolates of streptococci from bovine mastitis by pulsed-field gel electrophoresis.

Pulsed-field gel electrophoresis (PFGE) was examined as a tool to differentiate strains of streptococci isolated from clinical and sub-clinical cases of bovine mastitis. Analysis of SmaI chromosomal digests of Streptococcus agalactiae, S. dysgalactiae subsp. dysgalactiae and S. uberis isolates revealed intraherd and interherd strain relationships within each species. Comparison of S. agalactiae isolates from the same herd revealed little variability in their SmaI restriction patterns indicating a single strain originating from a common source of infection. However, comparison of S. agalactiae isolates between herds showed that each herd was infected with a distinct strain. The restriction profiles from S. dysgalactiae subsp. dysgalactiae and S. uberis were more diverse and often multiple strains of both species were present within an individual herd, with some herds containing more than one representative of a particular strain. Interestingly, it was only observed with S. dysgalactiae subsp. dysgalactiae that some strains were present in more than one herd. PFGE was found to be a useful and reproducible method for the discrimination of different strains of the three most important species of streptococci responsible for bovine mastitis and to offer a means to identify environmental sources of infection.

Animals↗
PubMed1994

Strategies for mastitis control: dry cow therapy and culling.

The effects of three selection strategies for dry cow therapy on prevention of new infections and rate of antibiotic usage were compared. Quarter infection status of 1044 cows in 12 herds was determined by bacteriological methods at drying off, calving and three to five months into the following lactation. Cows that were uninfected at drying off were randomly allocated to treatment (whole udder, dry cow therapy) and non-treatment groups. Infected cows were randomly allocated to whole udder or infected quarter only treatments. The strategies compared were blanket treatment (treat all quarters of all cows), selective cow treatment (treat all quarters of any cow infected in one or more quarters) and selective quarter treatment (treat infected quarters only). Selective cow treatment was identified as the preferred strategy. Blanket treatment resulted in increased antibiotic usage (15.5 vs 6.4 tubes per infection eliminated) with no additional benefit, and selective quarter treatment resulted in a higher new infection rate (6.4% vs 3.9% quarters) in the dry period. The prevalence of infection within a herd at drying off had no influence on new infection rates in the dry period or early lactation. The cure rate after dry cow treatment (mean of 66%) decreased significantly with increasing age (P < 0.001). Cows infected in the previous lactation contributed over 76% of infections at calving and nearly 70% at mid-lactation. To lower the incidence of mastitis in a herd, a greater emphasis on culling of older infected cows and prevention of new infections during lactation is needed.

Animals↗
PubMed1990

Effects of antibiotic therapy at drying off on mastitis in the dry period and early lactation.

Four strategies for selecting cows for intramammary therapy with benzathine cloxacillin at drying off were compared in 12 Victorian dairy herds. The bacteriological status of all quarters of all (1044) cows was determined just before drying off, within 2 d of calving, and again 3 to 5 months after calving. All cases of clinical mastitis (from calving to mid-lactation) were recorded. Cows not infected at drying off were allocated randomly to 2 subgroups of approximately 350 cows each: not infected, not treated (NI-NT), or not infected, all quarters treated (NI-AT). New infection rates in the dry period (3.8% for NI-NT vs 2.1% for NI-AT) and in early lactation (4.1% for NI-NT vs 3.9% for NI-AT) were low and these differences were not significant. Incidence of clinical mastitis in early lactation was almost 50% higher for the treated group of uninfected cows compared with the untreated group (0.05 less than p less than 0.1). Cows infected in one or more quarters at drying off were split randomly into 2 subgroups of approximately 170 cows each: infected, all quarters treated (I-AT), or infected quarters treated only (I-QT). The new infection rate during the dry period was nearly 4 times higher for I-QT (15.3%) due to significantly more new infections by Staphylococcus aureus and Streptococcus uberis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Haemoglobinuria and hypophosphataemia in postparturient dairy cows without dietary deficiency of phosphorus.

Postparturient haemoglobinuria occurred in 11 Holstein-Friesian cows in 8 dairy herds in East Gippsland, Victoria. The affected cows had a wide range of ages, body condition and production level. Seven of 9 cows sampled were hypophosphataemic, 4 of 8 cows examined had Heinz bodies present in erythrocytes and strong ketonuria was present in 6 of 10 urine samples tested. Herdmates having similar calving dates had mostly normal serum phosphorus levels and none had Heinz bodies. There was no evidence for dietary phosphorus (P) deficiency, hypocuprosis or excessive P drain from high production being predisposing factors. There were no cruciferous plants in the diet. Haemolysis persisted in 4 cows despite treatment to raise serum P levels. An hyposthesis is proposed for the sporadic nature and clinical manifestations of the disease. This is based on mechanisms of hypophosphataemia occurring in man and mechanisms of Heinz body formation and haemolysis in other circumstances. We suggest that hypophosphataemia occurs following recovery from preparturient keto-acidosis caused by undernutrition in late pregnancy and then becoming nutritionally replete in the early postparturient period. Circulating oxidants may cause erythrocyte damage which may be predisposed to by hypophosphataemia.

Animals↗
PubMed1984

The effect polyethylene intramammary devices on the somatic cell count and milk production of dairy cows.

Polyethylene intramammary devices (IMD) were inserted into all 4 quarters of 15 multiparous dairy cows. Fifteen cows, matched for parity and production, were controls. The insertion of IMD's was easily achieved and produced no adverse effects. Throughout the 150-day test period, the mean somatic cell count of cows with IMD's in situ was 216,000 cells per ml, compared with 119,000 cells per ml in controls (P less than 0.01). Total production of milk, butterfat and protein was not significantly different between the 2 groups. The new infection rate was too low to allow assessment of the value of the IMD for mastitis prevention.

Animals↗
PubMed1984

Colitis in sheep due to a Campylobacter-like bacterium.

Epidemic diarrhoea was observed in approximately 2,000 of 6,700 sheep on 9 farms. The disease, called weaner colitis, caused mortality of 1%, while morbidity varied from 20 to 75%. Colon contents from affected sheep were inoculated into 17 sheep, 13 of which developed diarrhoea 5 to 7 days after inoculation. Naturally and experimentally infected sheep had mild, erosive typhlitis and colitis. Microscopic examination of washed scrapings of colonic mucosa from all affected sheep revealed masses of curved bacteria that were not seen in controls. Electron microscopic examination showed similar bacteria adherent to colonic epithelium of an experimentally infected sheep. Curved, motile bacteria were isolated from 2 naturally occurring cases. One isolate was inoculated into 9 sheep, 2 of which developed diarrhoea. The other isolate was given to 4 sheep without observable effect. The curved bacteria grew only on media containing blood, in an atmosphere of approximately 10% air, 10% CO2 and 80% H2. They were Gram-negative, with a polar flagellum at one or both ends, they did not ferment glucose or give a positive catalase reaction. It is suggested that these bacteria are a new Campylobacter species and that they play a major role in the aetiology of weaner colitis.

Animals↗
PubMed1984

Diagnostic studies of the fetus, placenta and maternal blood from 265 bovine abortions.

During 1981, the fetus, placenta and maternal serum were received from each of 265 bovine abortions. These specimens were examined using histopathological, histochemical, bacteriological, mycological, endocrinological, immunological, serological and virological techniques. The cause of abortion was identified in 98 (37%) cases. Of these diagnosed abortions 27 (28%) were due to infection with fungi, 17 (17%) to Salmonella spp, 11 (11%) to Campylobacter fetus and 10 (10%) to Corynebacterium pyogenes infection. Of the remaining 33 (34%) diagnosed abortions 8 were due to Leptospira sp, 5 due to protozoan (probably Sarcocystis) encephalitis and 20 due to miscellaneous bacterial infections (including Brucella abortus) and fetal deformities. Bovine virus diarrhoea virus was isolated in 5 (2%) abortions, however the significance of the isolations was not known. Infectious bovine rhinotracheitis virus and chlamydia were not identified as causal agents in any abortion. In 18 (7%) abortions no definite etiologic agent was identified despite pathological findings suggestive of infection. Fetal heart blood serology and immunoglobulin values were not reliable indicators of infectious abortion. Of the remaining 149 (56%) abortions, 17% had high maternal serum cortisol levels and twin fetuses occurred in 9%.

Abortion, Septic↗
PubMed1981

An outbreak of listerial meningo-encephalitis in sheep.

An outbreak of ovine listerial meningo-encephalitis on sheep farms in eastern Gippsland, Victoria, during winter and spring 1978, is recorded. Cases were confirmed by histology of brain or by culture of Listeria monocytogenes from sheep on 21 farms. The morbidity rate in affected flocks ranged from 0.2% to 8.0%, and the case fatality rate was almost 100%. The peak incidence of disease followed a period of continuous heavy rain and flooding of grazing pasture, and the majority of affected flocks were located on poorly drained coastal sandy soil. There was evidence of concurrent debilitating disease in many of the cases submitted for laboratory confirmation of listeriosis.

Animals↗