Serological survey of chlamydial antibody in post-natal sera

Questionnaires (3426; 72.8%) and blood samples (3890; 82.6%) were analysed from 4704 women post-natally. The answers to the questionnaire confirmed that those patients living in areas with the highest percentage employed in agriculture were most likely to be in direct or indirect contact with sheep or sheep products. When the 788 (20.3%) of the sera with group specific antibody were examined for type-specific antibody, 291 (7.5%) reacted with Chlamydia trachomatis, 153 (3.9%) with Chlamydia pneumoniae, but only one (0.03%) with Chlamydia psittaci. Thus, it would appear that C. psittaci was not an important pathogen in this survey, despite the largest proportion of blood samples being submitted from those most likely to be employed in agriculture. However, in the course of this survey the three patients who had previously suffered chlamydia-associated abortion had successful pregnancies and submitted blood specimens. Serological studies on the serial bloods from these patients showed that, despite developing antibody to the C. psittaci pool and the ovine abortion strain of C. psittaci following abortion, this antibody waned. At the time of the subsequent successful pregnancy, serological results would not have detected a previous C. psittaci infection, but one due to C. pneumoniae. Thus, the results of a survey such as this must be interpreted with caution.