Efficacy study of soluble bacitracin (Bacivet S®) in a chronically infected epizootic rabbit enteropathy environment.

Abstract

The present study evaluated under field conditions the efficacy of bacitracin zinc soluble powder (Bacivet S®) for the treatment of Epizootic Rabbit Enteropathy (ERE). A blinded study was conducted in compliance with the ?Good Clinical Practice? guidance. The trial site was known to be chronically infected with ERE. A total of 384 weaned rabbits (30 days of age) were enrolled in the study. They were randomly distributed over 6 rows of cages located in the same experimental room. Two rows of cages remained untreated (control group), another 2 rows were treated with Bacivet S® for 14 days (T14) and 2 rows were treated with Bacivet S® for 21 days (T21). The medication was administered per row via the drinking water and initiated when at least one animal, showing clinical signs of ERE, died. The dose was adjusted daily according to the weight of the rabbits to achieve the target dose of 420 IU/kg body weight in the two treatment groups. Animals were observed daily for mortality, diarrhoea, tympany, or any other abnormal sign for 42 days post enrollment. Weights of the animals and feed intake were recorded on a weekly base. On the second day after the set-up of the trial, mortality already occurred with clear signs of ERE and the medication was initiated. On the primary evaluation parameter, mortality, both treated groups showed significant (P<0.01) better results than the control group with an overall mortality reaching 13.5%, 12.6% and 26.6% in T14, T21 and control groups, respectively. Considering only ERE confirmed mortality, differences were even more pronounced; 4.0% (T14), 6.3% (T21) and 14.1% (control), respectively. The occurrence of clinical signs (tympany and diarrhoea) was also reduced in medicated rabbits but this reduction was markedly higher for T21 treated rabbits (P<0.001 compared to control) than in the T14 group. A few days after the termination of the medication period, moderate mortality and clinical symptoms were observed in both medicated groups. These isolated cases were probably due to a recontamination through the untreated groups. Data of daily weight gain and feed intake showed a good agreement with the observed mortality and clinical symptoms. In conclusion, Bacivet S® proved its efficacy against ERE in a chronically infected environment for both tested treatment regimens.