Which assay is not used to diagnose Chlamydia psittaci in birds?

Which assay is not used to diagnose Chlamydia psittaci in birds?

• A. PCR
• B. Culture
• C. IFA
• D. ELISA

Answer: (D)

The main idea is how we confirm active infection versus mere exposure. For avian Chlamydia psittaci, diagnosing active disease relies on tests that directly detect the organism or its components: PCR looks for the bacterium’s DNA in samples, culture attempts to grow the organism in specialized labs, and IFA detects chlamydial antigens in specimens. ELISA, on the other hand, measures antibodies in the bird’s serum. A positive antibody test shows exposure and an immune response at some point, but it doesn't prove the bird is currently infected or shedding, and antibodies can persist after recovery or vary with timing of infection. Therefore, ELISA is not used to diagnose active C. psittaci infection in birds; it’s more suited for exposure surveillance or flock-level serology.

The main idea is how we confirm active infection versus mere exposure. For avian Chlamydia psittaci, diagnosing active disease relies on tests that directly detect the organism or its components: PCR looks for the bacterium’s DNA in samples, culture attempts to grow the organism in specialized labs, and IFA detects chlamydial antigens in specimens. ELISA, on the other hand, measures antibodies in the bird’s serum. A positive antibody test shows exposure and an immune response at some point, but it doesn't prove the bird is currently infected or shedding, and antibodies can persist after recovery or vary with timing of infection. Therefore, ELISA is not used to diagnose active C. psittaci infection in birds; it’s more suited for exposure surveillance or flock-level serology.