engleski

Chlamydia psittaci associated with pox virus infection in laying hen flock

In the autumn 2010 we investigated an outbreak of pox infection complicated with Chlamydia psittaci (C. psittaci) in a flock of free-ranged laying hens. Altogether 300 birds, kept as a backyard flock, started to show clinical signs of upper respiratory tract infection and severe purulent conjunctivitis was noticed in most of the birds. Mortality rate amounted up to 10% daily. Three laying hens were sacrificed and the samples were submitted to laboratory testings. The aerobic bacteriological examination revealed the presence of Bacillus sp. and Staphylococcus sp. in conjuntival, choanal and tracheal swabs. The conjunctival and pharyngeal swabs of two sacrificed laying hens were examined by Chlamydiaceae-specific real-time PCR, as described by Ehricht et al. (2006.) and by C. psittaci-specific real-time PCR, as described by Pantchev et al. (2008.), and reacted positive to both methods. Samples were also examined by inoculation in chicken embryos and the presence of pox virus in the chorioallantoic membrane was confirmed using specific PCR (Tadese et al., 2007.). The entire flock was treated with enrofloxacin (Enroxil 10%, Krka, Slovenija) via drinking water for 14 days and the symptoms resolved. Presence of poxvirus probably contributed to the severity of clinical signs caused by C. psittaci and enhanced the infection. Nevertheless, the pathogenicity of this C. psittaci strain remains indistinct, and we can only speculate that it could be higher then of other strains, infecting poultry. The infection route remained unclear, but due to the free-range production it could be possible that wild birds served as a source of infection or the pathogens persisted in the environment. The finding of C. psittaci in laying hens is of enormous importance from two standpoints: 1) significance for public health as a dangerous zoonosis, and 2) presence of C. psittaci in chickens which are supposed to be less prone species to this infection.

C. psittaci ; pox virus ; laying hens

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