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Escherichia coli (STEC) in healthy dairy ruminants was investigated between 1996 and 1998 by a multiplex polymerase chain reaction (mPCR) technique. A total of 13 552 E. coli colonies from 726 cows, 28 sheep and 93 goats out of 112 randomly selected dairy farms in Hessia, Germany were analysed. STEC strains were recovered from 131 (18Á0%) cows, nine (32Á1%) sheep and 70 (75Á3%) goats. Further characterization of the STEC isolates showed that 89 (0Á66% of the investigated colonies) of animal ®eld strains carried stx1 gene, 64 (0Á47%) stx2 gene and 57 (0Á42%) stx1 and stx2 gene. Sixty (93Á8%) out of 64 stx2 ®eld strains were harboured by cows. In contrast, 74 (83Á1%) out of 89 stx1 dairy animal ®eld strains were from ovine or caprine origin. Only 17 (8Á1%) stxpositive isolates (13 from cattle, three from sheep and only one from goat) were positive for eaeA gene. Eight (9Á0%) of the stx1, ®ve (7Á8%) of the stx2 and four (7Á0%) of the stx1/stx2 gene-positive ®eld strains carried the eaeA gene. The prevalence of EHEC-haemolysin (EHEC-hlyA) gene sequence was 88Á8% (79 isolates) of the stx1 and 68Á8% (44 isolates) of the stx2 isolates. Out of 57 stx1-and stx2-positive ®eld-strains, 34 (59Á6%) carried the EHEC-hlyA gene. E. coli O serovars O:157 and O:111 were not found. Only one isolate was positive with O26 antiserum.

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The objective of this field study was to compare the udder health status as well as the clinical mastitis rate during the first 100 d of lactation in cows that received long-acting dry cow antibiotic alone (group AB) or in combination with an internal teat sealant (group AB + OS). The study was conducted during a 9-month period and included 136 Holstein cows from 12 dairy farms in Hessia, Germany. Between days 1 and 5 after calving a California mastitis test (CMT) was performed. Milk-samples were collected for bacteriological culture before drying off, between days 6 and 14 and days 35 and 56 of lactation. Additionally the cows were monitored for the occurrence of clinical mastitis events until 100 d post partum. Within the 12 herds cow-pairs were formed on the basis of age, milk yield and SCC. A cow-pair consisted of one cow from group AB and one cow from group AB + OS. For statistical analysis within every cow-pair one quarter that has been dried off with internal teat sealant and dry cow antibiotic (group AB + OS) was compared with one quarter that has been dried off with dry cow antibiotic (group AB) alone. As criterion for the matching process of udder quarters the cytobacteriological udder health status before drying off was used. A total of 544 quarters (136 cows) were used in this analysis. In the first 5 d after calving, group AB had significantly more quarters with a positive CMT reaction than group AB + OS (85 vs. 57; P <0·001), and in the first 100 d of lactation, group AB had more quarters with clinical mastitis than group AB + OS (25 vs. 15; P = 0·03). In the time periods 6-14 and 35-56 d of lactation, there were fewer quarters in group AB + OS populated with Corynebacterium spp. (days 6-14, P = 0·05; days 35-56, P = 0·02) and aesculin-positive streptococci (days 35-56, P = 0·02). The internal teat sealant was a promising tool for the prevention of new intramammary infections (IMI) of dry cows with environmental udder pathogens as expressed during early lactation.

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