Abstract
Outbreaks of calf diarrhea occurred on three dairy farms in Shiga Prefecture in the spring in 1980. Escherichia coli strains producing heat-stable enterotoxin (ST)were isolated in pure culture and at high frequency from the intestinal contents and parenchymatous organs of dead calves. Most of these strains were typed as 0101-K99. All the strains were non-motile and typed as biovar B. They were resistant to two drugs, tetracycline (Tc) and chloramphenicol (Cm) or six, Tc, Cm, streptomycin (Sm), sulfadimethoxine (Su), kanamycin (Km), and ampicillin (Ap), and contained R plasmids. With the properties of these ST-producing (ST+) strains as indicators, the ST+ strain contents of the intestines were compared between diarrheal calves and healthy cows kept in the same barn. The total E. coli count per gram of diarrheal feces of calves was 108.9, most of which were ST+ strains. The count in the rectal feces of healthy calves was 107.1, of which 105.6 were ST+, while that in the rectal feces of healthy cows was 106.2, of which 103.3 were ST+. These results suggest that ST+ strains with the same properties were distributed widely not only among diarrheal calves but also among healthy cattle kept in the same bars on the three farms where the outbreaks of calf diarrhea occurred.
