[Pathogenic role of strains of specific Escherichia coli serotypes in the development of mastitis in cows. I. Clinical course].

The studies were carried out on 14 cows. For infection of the cows pathogenic (from the field) E. coli strains from the serological groups: 093, 010,086 and non pathogenic strains (museum) belonging to serogroups: 0132, 0120, 093 were used. The microorganisms of each group were injected into the udders of two cows. Two successive cows were injected into the udders E. coli endotoxin (group 093). In 6 hr after infusion of the strain or endotoxin, the experimental quarters were swollen, reddened, became hot, painful and hard. The internal temperature values (40,9-41,7 degrees C), pulse rate (100-120) and breathing rate (over 40) rapidly increased. The animals stopped taking food and ruminating. There appeared convulsions, serous discharges from the nose and eyes, sialorrhea, diarrhea. Then the general symptoms disappeared after 9 hr in cows which received endotoxin, and after 12 hr in cows infected with the museum strains. However, the cows infected with the field E. coli strains showed a very weak appetite for 2-4 days, despite the temperature dropped. After the general symptoms disappeared, changes in the experimental udder quarters were intensified and then they were observed to retreat. During 10 days the disease symptoms disappeared in the cows which were given endotoxin. These symptoms persisted longer (up to 14 days) in cows infected with the museum strains. However, in cows infected with the field strains (particularly from group 093) the inflammatory state in the udder lasted till the end of 14-day observation.