Digestive pathway of infection in Streptococcus dysgalactiae polyarthritis in lambs

A sheep farm situated in the north-east of Spain suffered an outbreak of polyarthritis in lambs from May 2006 until September 2007. The percentage of affected animals at the beginning of the outbreak was 5.71%. This percentage decreased to 1.42% by September 2007.Samples of joint fluid were colleted for culture, and antibiotic susceptibility testing was performed. Streptococcus dysgalactiae was isolated in microbial culture and the testing revealed resistance to tetracycline, a commonly used antibiotic in the treatment of arthritis in sheep. Affected lambs were treated with parenteral lincomycin and dexamethasone with satisfactory results.Nasal, auricular and vaginal samples were collected from 30 ewes in order to evaluate these locations as a reservoir for the bacteria in sheep. No isolation of S. dysgalactiae was obtained from these areas.S. dysgalactiae is also considered an environmental cause of clinical and subclinical mastitis in sheep. Milk samples from 95 affected ewes were collected during the same period of time (20 suffering from clinical mastitis and 75 subclinical mastitis, after performing California Mastitis Test on 400 milking ewes). S. dysgalactiae was isolated in pure culture from the milk sample of one ewe, the mother of a polyarthritic lamb.S. dysgalactiae has been reported as a cause of polyarthritis in calves and goats and it should be considered as a relevant cause of polyarthritis in lambs, the digestive tract being, probably, the main pathway of infection.