Abstract
From 1986 to 1995, we performed drug sensitivity tests on 329 cattle with respiratory infectious disease to indentify the causative bacteria, and we conducted both in vitro and in vivo experiments to determine the effectiveness of various combinations of antibacterial drugs for treating respiratory infectious disease in cattle. Pasteurella, Mycoplasma or Ureaplasma were isolated from 271 (82.4%) of the cattle, and 38% (105/271) of these cattle were infected with a combination of Pasteurella and Mycoplasma or Ureaplasma. Results of tests conducted on cattle in the field to determine the efficacy of administration of only one widely used drug (ampicillin, oxytetracycline, kanamycin or thiamphenicol) for the treatment of respiratory infectious disease were not satisfactory. Therefore, we examined the antibacterial effect of a combination of thiamphenicol (TP), Tylosin (TS) or lincomycin on P. multocida, P. haemolytica and M. bovis in vitro using the checker board method and FIC index. The FIC index for either combination of two of the drugs against the bacteria was less than 1.0 (0.06-1.0), and the combination of these drugs showed a synergistic or additive effect. Moreover, improvement in symptoms was more rapid and the cure rate was significantly higher in cattle treated with a combination of TP and TS than in cattle treated with other antibiotics.
