IMPORTANCE OF ESCHERICHIA-COLI IN YOUNG BEEF-CALVES FROM NORTHWESTERNQUEBEC

The objectives of this study were: (i) to investigate the prevalence o f Escherichia coli producing F5 (K99), F41, or F165 fimbriae and STa e nterotoxin; (ii) to determine serum antibody levels against these fimb riae; (iii) and to examine the association between bacteriological and serological results and the presence of diarrhea, in beef calves from northwestern Quebec, A total of 373 live three to four week old calve s and 27 dead calves were sampled between January and March 1991. No i solates positive for F5 were detected in live calves, and only one E. coli producing STa and F41 was isolated. Escherichia coli producing F4 1-like surface antigens or F165 fimbriae were isolated from 17.43% and 5.63% of live calves, respectively. Antibodies against F5, F41 and F1 65 were low. Escherichia coli isolates positive for F41-like surface a ntigen were most often observed in calves born between January and Mar ch. No association was found between bacteriological and serological f indings, nor between these findings and diarrhea. Calves born from dam s vaccinated against E. coli had higher median antibody levels than th ose born from unvaccinated darns. No E. coli positive for F5 or F41 fi mbriae were isolated from dead calves. Escherichia coli with F41-like surface antigen or F165 were found in 55.56% and 11.11% of ileal sampl es; 4% and 16% of cecal samples, and 0% and 7.4% of colon samples, res pectively. Escherichia coli positive for F41-like surface antigen were detected significantly more frequently in the ileum (X(2dr)(e)= 31.01 , p < 0.001).