THE DURATION OF IMMUNITY AFTER VACCINATION WITH A SINGLE DOSE MYCOPLASMA HYOPNEUMONIAE VACCINE AND THE EFFECT OF SEROLOGICAL STATUS ON LUNG LESION SCORES
A. Dawson, S. Thevasagayam, J. Sherington, J.D. Mackinnon, L.P. Stipkovits and A.R. Peters

Abstract
The duration of immunity induced by a single dose Mycoplasma hyopneumoniae vaccine (Stellamune? Once) was investigated in pigs vaccinated at approximately 3 and 5 weeks of age. Liveweight gains, coughing rates and lung lesions at post-mortem examination were compared between controls and vaccinates challenged at approximately 21 and 26 weeks of age. Three of four vaccinated groups showed significant reductions in lung lesions (55-86%) compared with their contemporary controls. In a fourth comparison, the induced lung lesion scores in the controls were relatively low and the reduction was not statistically significant in the vaccinates (4.4 vs 1.1%; P<0.07).
???? There were significant beneficial effects on liveweight gain and coughing rate in 2/4 vaccinated groups. In a second study, the lung lesion response to vaccination was assessed in groups of seronegative and seropositive pigs 4 weeks after challenge. Overall, there were significant reductions of 50-60% in lung lesion scores in vaccinates compared with controls <0.05). The interaction between serological status and vaccination was not significant (P=0.3) showing that the effects of vaccination were not influenced by the presence of maternal antibody. It is concluded that the vaccine confers a duration of immunity of up to 23 weeks and that protection can be induced in the presence of maternally derived serum antibodies.

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