Study finds turkeys most susceptible in cross-species C. psittaci spread

A newly posted study in Frontiers in Veterinary Science suggests Chlamydophila psittaci can move efficiently from infected broiler chickens to several other avian species under experimental contact conditions, with turkeys showing the greatest susceptibility. The paper adds fresh data to a long-running concern in poultry medicine: that avian chlamydiosis can circulate across species boundaries while also posing a zoonotic risk to people who handle birds. (frontiersin.org)

In the study, researchers divided 90 one-day-old birds into six groups of 15: a challenged broiler group, an unchallenged broiler control group, and groups of ducks, turkeys, pigeons, and quails. At 7 days of age, the challenged broilers were inoculated intranasally with C. psittaci. Once signs developed in those chickens, three infected chicks were transferred into each of the other species groups to test contact transmission. According to the article abstract page, exposed birds developed clinical signs within 3 to 5 days. (frontiersin.org)

The key finding was the species gradient in apparent susceptibility. Turkeys had the highest burden of illness in the experiment, with depression reported in 14 of 15 birds and respiratory signs in 13 of 15. Chickens were less affected, and ducks, pigeons, and quails were the least susceptible in this setup, with 5 of 15 birds affected in each of those groups. Postmortem lesions followed the same pattern, with the most severe pathological changes seen in turkeys. (frontiersin.org)

That hierarchy broadly fits existing reference material, even if the experiment itself was tightly controlled and may not map perfectly onto field conditions. Merck Veterinary Manual notes that among domestic species, turkeys and ducks are often affected, that infection is endemic in commercial turkey flocks, and that chickens are relatively resistant to developing clinical disease, with subclinical infection common. WOAH also emphasizes that clinical severity varies by species, age, and strain, and that many poultry may shed the organism without obvious signs. (merckvetmanual.com)

The public health angle remains important. CDC says people who work with birds, including poultry farmers, processing plant workers, and veterinarians, are at increased risk for psittacosis, and that transmission usually happens by inhaling dust from dried secretions or droppings. A systematic review of zoonotic transmission sources also found evidence linking human psittacosis to poultry species including turkeys, chickens, and ducks, reinforcing the One Health relevance of any data that clarifies which birds may amplify exposure risk. (cdc.gov)

Why it matters: For veterinary professionals, this study is less about a surprise pathogen than about risk ranking. If turkeys are more clinically susceptible after exposure from infected broilers, mixed-species rearing, commingling, live-bird movement, and shared equipment or airspace deserve closer scrutiny in surveillance plans. The findings also support a practical reminder: low-clinical-sign species may still matter epidemiologically if they become infected and shed intermittently. Because APHIS lists avian chlamydiosis as a monitored, reportable disease in the U.S., and because no commercial poultry vaccine is available, prevention still leans heavily on biosecurity, diagnostics, reporting, and occupational protection. (aphis.usda.gov)

There wasn't much direct expert reaction to this specific paper available yet, which isn't unusual for a newly posted study. But established guidance from NASPHV and CDC continues to frame C. psittaci as both an animal health and human health issue, especially where birds are housed densely or handled frequently. That makes the paper most useful as a signal for poultry veterinarians, diagnosticians, and integrators thinking about species mixing and differential susceptibility, rather than as a standalone basis for immediate practice change. (nasphv.org)

What to watch: The next questions are whether the authors publish fuller diagnostic and pathology details in the final formatted version, whether field studies replicate the turkey signal under commercial conditions, and whether regulators or industry groups incorporate mixed-species C. psittaci risk more explicitly into surveillance and worker-protection guidance. (frontiersin.org)