DIFFERENCES IN INTRAMAMMARY PATHOGENICITY OF FOUR STRAINS OF STREPTOCOCCUS DYSGALACTIAE

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Abstract
Streptococcus Dysgalactiae has long been recognised as an udder pathogen. It was first described by Diernhofer (1932) and subsequently classified as a group-C streptococcus by Lancefield (1933). It can be found in various extramammary sites, including the vagina (Francis, 1941) and tonsils (Daleel and Frost, 1967) of adult cattle, but the significance of these sites as reservoirs of infection in a herd is not known. Udder infection with S. dysgalactiae is generally less frequent than with either S. agalactiae or S. uberis (Slanetz and Naghski, 1940). Results from 32 herds in the United Kingdom showed that 2.9% of cows were infected with S. dysgalactiae compared with 4.0% and 4.4% for S. agalactiae and S. uberis respectively (Wilson and Kingwill, 1975). McDonald and McDonald (1976) found that 41 of 455 (9%) streptococcal isolates from infected udders were S. dysgalactiae compared with 7 (1.5%) for S. agalactiae and 257 (56%) for S. uberis.

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