An outbreak of Streptococcus canis mastitis in a dairy herd in Israel.

CASE HISTORY An increase in the bulk somatic cell count (BSCC) of up to 1,000 x 103 cells/ml occurred in a dairy herd in Israel at the end of 2001 and beginning of 2002. CLINICAL FINDINGS Bacteriological examination of milk from 69 cows revealed a high prevalence of Streptococcus group G bacteria, identified as S. canis, affecting 38% of cows and 20% of all quarters. Isolates were sensitive to cephalothin and moderately sensitive to penicillin G. Infected cows were separated from the herd, treated with intramammary antibiotics, milked last, and strict hygiene practices were introduced to the milking routine. The pathogen was cleared from the herd and BSCC decreased to 250-350 x 103 cells/ml after 6 months. DIAGNOSIS Streptococcus canis mastitis. CLINICAL RELEVANCE Streptococcus canis infection may cause subclinical mastitis and high bulk SCC in dairy herds and be resolved by treatment with intramammary antibiotics and the introduction of strict hygiene practices.