Molecular detection of <i>Chlamydia psittaci</i> in birds: a systematic review

Molecular methods are currently the most sensitive for detecting <i>Chlamydia psittaci</i> in birds. Most laboratories have developed their own molecular assays or adapted published protocols, often making slight modifications to fit their specific study purposes. The sensitivity and specificity of a molecular test depend on the target gene, primer sequences, types of molecular test, DNA extraction method, and sampling methods. We reviewed 120 articles published between 2000 and 2020 to compile information on the molecular detection of <i>C. psittaci</i> in birds. Of the ten genomic targets currently available to detect <i>C. psittaci</i> in birds, the <i>ompA</i> gene was the most widely used. In published surveillance studies, of the fourteen molecular test types, conventional PCR and quantitative PCR were applied the most. A testing strategy using a hierarchical approach that includes molecular tests of genus- and species-specific targets is recommended to detect other avian chlamydial species besides the well-recognized <i>C. psittaci</i>. Samples should be sourced from both the respiratory and gastrointestinal tracts whenever possible for better accuracy. High-quality DNA can be obtained when the sample is preserved in optimal medium and temperature, and an optimized DNA extraction protocol is applied. Standardization and validation of molecular <i>Chlamydia</i> tests are needed to enhance the comparability and reliability of assays to detect <i>C. psittaci</i> and other chlamydiae species in birds. <b>RESEARCH HIGHLIGHTS</b>Hierarchical molecular testing is recommended for the detection of avian <i>C. psittaci</i>.Key molecular tests for surveillance were conventional PCR and quantitative PCR.The most used genomic target to detect <i>C. psittaci</i> in birds was the <i>ompA</i> gene. Hierarchical molecular testing is recommended for the detection of avian <i>C. psittaci</i>. Key molecular tests for surveillance were conventional PCR and quantitative PCR. The most used genomic target to detect <i>C. psittaci</i> in birds was the <i>ompA</i> gene.