Field efficacy of a combined use of Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae vaccines in growing pigs

The effectiveness of simultaneous administration of commercial Mycoplasma h yopneumoniae and Actinobacillus pleuropneumoniae vaccines was tested in an indoor commercial piggery which had experienced continuing respiratory-dise ase problems confirmed as due to both of these pathogens. Piglets were rand omly assigned in equal numbers to vaccination and control groups, and each vaccine was administered at a separate site to assigned piglets at two and four weeks of age. Live weight of vaccinates immediately prior to slaughter was 2.49 kg higher (p = 0.04) than for controls at equal mean slaughter age of 132 days. Aver age daily gain (ADG) from 16 weeks to slaughter of vaccinates was also sign ificantly higher (33 g/day) than in controls (p = 0.05). Daily gain was not significantly different in younger age groups. Active enzootic pneumonia l esions were more likely in control than in vaccinated pigs. There were no s ignificant differences between vaccination groups with regard to severity o f pleurisy or presence of pleuropneumonia lesions at slaughter. Log-linear modelling was used to test the statistical association between v accination, enzootic-pneumonia lesions, pleurisy lesions and pleuropneumoni a lesions. It showed a reduction in the severity of enzootic pneumonia lesi ons for vaccinated pigs, and the presence of pleuropneumonia lesions increa sed the likelihood of pleurisy lesions. No other association was significan t, and no evidence of synergy between the vaccines in influencing lesion se verity for pleuropneumonia was detected (within the limitations set by the trial design). (C) 1999 Elsevier Science B.V. All rights reserved.