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Factors Affecting the Frequency of Isolating Streptococcus Agalactiae from Herd Milk Supplies and the Control of the Organism in the Dairy Herd

1979; Elsevier BV; Volume: 135; Issue: 2 Linguagem: Inglês

10.1016/s0007-1935(17)32933-0

1879-3606

J.K.L. Pearson, D.A. Pollock, D. Greer,

Neonatal and Maternal Infections

The prevalence of Str. agalactiae throughout the world is summarized in relation to the need for adequate monitoring systems which might be helpful to those who wish to initiate control systems. While some countries have made considerable progress towards eradicating the organism from dairy herds, others have appeared to make none at all. Fifty-one herds comprising 862 cows were studied in Northern Ireland, the incidence of Str. agalactiae being monitored by monthly culturing of the bulk milk supply for a full year. The frequency of isolations per month varied from 0 to 12 and was correlated with the percentage of infections and latent infections in cows and quarters using strict techniques and definitions. 3400 quarter milk samples were cultured, the overall number of cows infected being 27% and quarters 11∙7%. The inclusion of Str. agalactiae ‘isolates’ increased these percentages to 33 and 16% respectively. On statistical analysis better correlations were obtained using infections alone than when isolations from quarter samples were included, the results being very highly significant (P < 0∙001) with both cows and quarters. When sample isolations were included the correlation coefficients were marginally lower and in the case of cows was significant only at the 0∙01 level. The limitations of testing the bulk-supply milk of herds monthly are illustrated and compared with the work of others in this field. The significance of cultural methods and the lack of standardized methods for monitoring Str. agalactiae in herds are discussed, particularly in relation to the adoption and economics of control methods. Reasons are put forward as to why the infection is still a serious problem in many parts of the world, including the United Kingdom, together with recommendations as to how the organism can be better controlled in the national and individual herd.