Effect of Mycoplasma iowae infection on the immune system of the young turkey.

Studies were conducted in turkey poults of the effect of Mycoplasma iowae on the humoral antibody response to sheep red blood cells (SRBC) and on the weight and histological appearance of the bursa of Fabricius. Day-old turkeys were infected with M. iowae via the air sac and control turkeys received sterile broth. In the first experiment infected and control birds were inoculated intravenously with SRBC at 12 and 33 days of age, and hemagglutination (HA) tests were carried out on serum collected at intervals. Infected birds showed a slightly delayed response compared with control birds, but there was no delay in secondary response. Moreover, those birds with clinical disease gave significantly higher peak HA titres than did clinically healthy birds. In the second experiment the body weight and bursa to body weight ratio of M. iowae infected turkeys were compared with those of the control birds at 7 and 21 days of age. There was no significant difference in body weight, but at 7 days the mean bursa to body weight ratio of infected birds was significantly less (P less than 0.01) than that of the control birds and microscopic changes were seen in some bursae. These preliminary observations suggest that M. iowae infection of young turkeys may cause temporary damage to the bursa of Fabricius, accompanied by a transient immunosuppression.