What is the treatment of choice for Chlamydia psittaci in birds?

• A. Azithromycin
• B. Doxycycline
• C. Enrofloxacin
• D. Chloramphenicol

Answer: (B)

Chlamydia psittaci is an intracellular pathogen, so the treatment must be a drug that penetrates and stays active inside host cells. Doxycycline fits this need best because it concentrates in macrophages and reticuloendothelial tissues where the bacteria replicate, and it inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. This intracellular activity makes it widely effective in birds and allows it to reduce both clinical disease and shedding when given for an extended course, typically several weeks (commonly around 6 weeks or about 45 days) and continued after signs resolve and shedding has stopped. In practice, doxycycline is given orally, often in water or feed, with environmental decontamination and quarantine to prevent spread.

Other options have limitations: enrofloxacin is less reliably effective against intracellular Chlamydia; chloramphenicol can cause serious bone marrow suppression in birds and is typically avoided; azithromycin may be used in some cases but is not as consistently effective in avian Chlamydia infections.