[Avian Chlamydia psittaci phyla and their pathogenic significance for turkeys]

The present study demonstrates that Chlamydia psittaci is an important cause of respiratory disease in turkeys in Europe. The serotyping of isolates revealed that European turkeys frequently become infected with Chlamydia psittaci serovar D strains, but also can become infected with serovar A and B strains. In turkeys, differences in pathogenicity were observed not only between strains belonging to the serovars A (strain 84/55), serovar B (strain 89/1326) and serovar D (Texas Turkey strain and strain 92/1293), but also between two strains belonging to the same serovar D (Texas Turkey strain and strain 92/1293). In order to find an explanation for these differences in pathogenicity, the pathogenesis of the infection was studied in specific pathogen free turkeys. However, for all three serovars examined a similar pathogenetic sequence of events was deduced. In order to try and elucidate the observed differences in pathogenicity between different Chlamydia psittaci strains, the bacterium-host cell interaction was studied in BGM cell culture using transmission electron microscopy and immuno electron microscopy. Strains most pathogenic for turkeys, namely the serovar A strain and strain 92/1293 (serovar D) produced significantly larger inclusions with more numerous infectious organisms, produced the most severe degenerative changes in the host cell an also replicated freely in the cytoplasm of the host cell.