Intraperitoneal vaccination of pigs to control Mycoplasma hyopneumoniae

In a field trial at a commercial piggery 22 pigs were vaccinated intraperitoneally, at 30 days and 60 days old, with formalin-killed Mycoplasma hyopneumoniae plus adjuvant. Two other groups of the same size, one receiving a ration containing antibiotics, were not vaccinated. The mean enzyme-linked immunosorbent assay (ELISA) ratio of the vaccinated group increased significantly (P less than 0.001) after 30 days, and continued to rise until day 156 of life. In the other two groups the ELISA ratio did not increase significantly until day 115. The vaccinated pigs in the 30-day period after the first vaccination grew significantly (P less than 0.01) more slowly than the controls but between days 60 and 144 they grew significantly faster (P less than 0.05) than the two other groups, thus compensating for their previous, relative loss. At slaughter (at 163 days old), the mean weight was similar in all groups. The mean score for pneumonia at slaughter for the vaccinated, medicated and control groups was 2.6 (+/- 4.3), 9.4 (+/- 14.0) and 10.5 (+/- 12.4), respectively. The proportion of M hyopneumoniae-affected lungs (4.8 per cent) in vaccinated pigs, as judged by immunofluorescence, was significantly less (P less than 0.001) than the control groups (40 per cent). Thus, intraperitoneal vaccination with killed M hyopneumoniae plus adjuvant might control mycoplasmal pneumonia in commercial piggeries.