Treatment of persistent intramammary infections with Streptococcus uberis in dairy cows.

A survey was conducted of the prevalence of environmental pathogens, especially Streptococcus uberis, as causes of clinical mastitis in dairy cows. The response of intramammary infections with S uberis to conventional treatment was monitored by taking milk samples for bacteriology and somatic cell counting seven, 14 and 21 days after the treatment. The results showed that 51 per cent of the infections failed to respond, and the odds of cases failing to respond was significantly increased when the individual quarter somatic cell count seven days after the treatment was greater than 201,000 cells/ml. Ninety-six per cent of the suspected S uberis isolates identified by culture were confirmed as S uberis by using the api 20 Strep system. Restriction endonuclease fingerprinting was used to type the strains of S uberis isolated from 75 milk samples from 32 cows. Analysis showed that 96 per cent of the cases of S uberis that failed to respond to conventional treatment were persistent infections with one strain rather than reinfections with different strains. The persistent cases of S uberis were treated further with an extended course of intramammary preparations containing either procaine penicillin with dihydrostreptomycin or cefquinome. There was no significant difference between the cure rates achieved by the two preparations, and 55 per cent of the cases that had failed to respond to conventional treatment responded to the additional treatment.

Observations on ascites in nine cattle.

Signs of ascites were observed in only nine of 1863 cattle examined over a period of five years. The ascites was most commonly associated with either primary or secondary cardiac disease; cattle with ascites have a poor prognosis because the condition is usually assocaited with terminal disease. Two animals had cor pulmonale with chronic pneumonia, three had cardiomyopathy, one had bacterial endocarditis, two had thrombosis of the caudal vena cava and one had diffuse abdominal epithelioid mesothelioma.

Use of clinical information to predict the characteristics of bacteria isolated from clinical cases of bovine mastitis.

Farmers recorded the clinical signs of cows with clinical mastitis and submitted milk samples for bacteriological examination, so that the clinical signs could be correlated with the bacteriological findings. Odds ratios for the demeanour of the cow, the appearance of the milk, milk yield, udder texture, and the administration of parenteral antibiotics were calculated for mastitis cases classified in terms of their microbiology as either enterobacteriaceae, major Gram-positive pathogens, minor pathogens, 'no growths' or 'all other pathogens'. Animals infected with enterobacteriaceae had the highest odds of being reported as having a reduced milk yield, swollen or hard udders, watery milk and/or being systemically sick. A logistic regression model was used to predict the Gram-staining characteristics of the bacteria causing clinical mastitis. The clinical findings found to be significant predictors in the model were the demeanour of the cow and its milk yield. The regression model was used as a basis for a predictive test. Using a test data set, the sensitivity of the test was 28 per cent, its specificity was 96 per cent, the positive predictive value was 74 per cent and the negative predictive value was 80 per cent. The overall accuracy of these predictions was 79 per cent.