A cross sectional study on Dutch layer farms to investigate the prevalence and potential risk factors for different Chlamydia species.
Authors: Heijne Marloes, van der Goot Jeanet A, Fijten Helmi, van der Giessen Joke W, Kuijt Eric, Maassen Catharina B M, van Roon Annika, Wit Ben, Koets Ad P, Roest Hendrik I J
Journal: PloS one
Summary
# Editorial Summary Dutch researchers conducted a cross-sectional survey of 151 layer farms to establish baseline prevalence data for Chlamydia species, a zoonotic pathogen of significant public health concern. Pooled faecal samples from each farm were screened using generic and species-specific PCR, with throat swabs collected voluntarily from 69 farm workers; notably, *Chlamydia gallinacea* was detected on 47% of farms, whilst *C. psittaci* and *C. avium* were absent. Farm-level risk factors independently associated with *C. gallinacea* presence included older hen populations, use of bedding material, and—intriguingly—proximity to horses, though the mechanism underlying this equine link remains unexplained and warrants further investigation. The absence of Chlamydia DNA in all human throat samples suggests minimal occupational transmission risk under current farming practices, though detection in environmental samples indicates potential for exposure should hygiene protocols lapse. These findings establish *C. gallinacea* as the dominant Chlamydia species in Dutch layer production and highlight the need for enhanced biosecurity measures, particularly on farms with older birds and mixed livestock enterprises, pending clarification of zoonotic potential and whether clinical manifestations emerge under specific management conditions.
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Practical Takeaways
- •C. gallinacea is highly prevalent on Dutch layer farms (47%) but appears subclinical; farmers and veterinarians should not rely on clinical signs to identify infected flocks
- •The association with horse presence warrants investigation into horses as a reservoir or risk factor for farm contamination
- •Current evidence does not support C. gallinacea as a significant occupational zoonotic risk for poultry farm workers, though ongoing surveillance is warranted
Key Findings
- •C. gallinacea was detected on 71 of 151 farms (47%) while C. psittaci and C. avium were not detected on any farms
- •Risk factors for C. gallinacea presence included older hen age, use of bedding material, and presence of horses on the farm
- •C. gallinacea detection was not associated with clinical respiratory signs, ocular discharge, nasal discharge, diarrhoea, or increased mortality
- •No evidence of zoonotic transmission detected: all 69 human throat swabs from farm workers tested negative for Chlamydia DNA