A SURVEY OF BIRDS IN DENMARK FOR THE PRESENCE OF PNEUMOCYSTIS-CARINII

One hundred eighty three toluidine blue O-stained necropsy lung imprin t smears from different avian species were examined microscopically fo r Pneumocystis carinii. No cyst forms of the organism could be identif ied. Seventy-eight serum samples from a total of 155 chickens were exa mined by a competition enzyme-linked immunosorbent assay (ELISA) for a ntibodies to P. carinii; 53 serum samples were from individual chicken s, and 25 samples were pools of sera from two to five chickens. Dilute d 1:50, the 78 serum samples showed a specific ELISA-inhibition of 4% to 56% (the 95% confidence limit being 25% to 30% inhibition). Diluted 1:50, nine serum pools representing 34 chickens and 17 of the 53 indi vidual serum samples (32.1%) showed an inhibition greater than 30%. No specific pneumocyst DNA could be detected in serum from 13 of the 53 chickens using polymerase chain reaction and dihydrofolate reductase g ene as a specific probe. Specific antibodies to a 116,000 molecular we ight antigen of rat pneumocysts were shown in two (13.3%) of 15 indivi dual chicken serum samples. The results indicate that P carinii organi sms do not commonly reside in the lungs of birds, although some birds may be exposed to external sources of organisms.