The clinical efficacy of enrofloxacin was tested in calves with experimentally induced pneumonic pasteurellosis.
A strain of Pasteurella haemolytica, biotype A, serotype 1 (P haemolytica A 1), which had
been isolated from an outbreak of pneumonic pasteurellosis in feedlot calves, was used to induce
the disease in 24 eight-month-old calves. Each animal received, by intratracheal injection, 6 x 10<sup>11</sup>
colony forming units of P haemolytica A 1 in a four-hour log phase culture. Twelve similar animals were
kept as non-infected controls (Negative Control group). Treatment of the infected animals commenced
40 h after infection and was as follows: 12 animals each received 2,5 mg/kg enrofloxacin subcutaneously
and 12 animals each received 5 ml sterile saline intramuscularly (Positive Control group). All
treatments were given once daily for three consecutive days. Clinical examinations were performed
on all animals once daily, starting prior to infection and continuing until 12 d post-infection. The parameters
evaluated were rectal temperature, habitus (attitude), ocular mucous membrane congestion
and abnormal sounds on lung auscultation. On day14 post-infection, all animals were killed and
their lung lesions (if any) estimated as the percentage involvement of each pair of lungs. The only
statistically significant (P≥ 0,05) differences observed were between the Negative Control group and
the Positive Control group. Noticeable differences were seen between the enrofloxacin-treated group
and the Positive Control group, but they were not statistically significant (P> 0,05). The average lung
lesion score (pneumonic lesions as a percentage of total lung volume) for the Positive Control group
was 12,1 % and that of the enrofloxacin-treated group, 8,4 %. This difference was not statistically significant
(P > 0,05) .
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