Experimental infections with Actinobacillus pleuropneumoniae in pigs - I. Comparison of five different parenteral antibiotic treatments

SPF pigs aged 10 weeks were infected intranasally with Actinobacillus pleur opneumoniae serotype 2. After the onset of clinical symptoms of respiratory disease, which occurred 20 h post-infection, parenteral treatment with cef tiofur, danofloxacin, enrofloxacin, penicillin or tiamulin was initiated (n = 8 per group). Untreated groups, of which one was infected, sen ed as con trols. The uninfected control group did not show any signs of disease, whil e the infected control group was severely affected by the infection and als o expressed a decreased weight gain following the challenge. Based on clinical signs, the magnitude of pathological lesions in the respi ratory tract found at necropsy performed 17 days post-infection and the num ber of reisolates of A. pleuropneumoniae made at necropsy, treatments with the quinolones (danofloxacin and enrofloxacin) and the cephalosporine (ceft iofur) were superior to those with penicillin and tiamulin. The latter grou ps also developed antibodies to A. pleuropneumoniae to a larger extent. Som e of the pigs treated with ceftiofur and danofloxacin developed antibodies to A. pleuropneumoniae, and the microbe was reisolated from approximate to 50% of these animals. In contrast, pigs treated with enrofloxacin did not d evelop antibodies to A. pleuropneumoniae and the challenge strain was not f ound at necropsy. The performance with respect to daily weight gain and feed conversion corre sponded well with the clinical signs developed and the findings made at nec ropsy. The decreased growth recorded during the acute phase of the disease was, to a large extent, caused by a reduced feed intake.