Wild birds are considered as a reservoir for avian chlamydiosis posing a potential infectious threat to domestic poultry and humans. Analysis of 894 cloacal or fecal swabs from free-living birds in Poland revealed an overall Chlamydiaceae prevalence of 14.8% (n = 132) with the highest prevalence noted in Anatidae (19.7%) and Corvidae (13.4%). Further testing conducted with species-specific real-time PCR showed that 65 samples (49.2%) were positive for C. psittaci whereas only one was positive for C. avium. To classify the non-identified chlamydial agents and to genotype the C. psittaci and C. avium-positive samples, specimens were subjected to ompA-PCR and sequencing (n = 83). The ompA-based NJ dendrogram revealed that only 23 out of 83 sequences were assigned to C. psittaci, in particular to four clades representing the previously described C. psittaci genotypes B, C, Mat116 and 1V. Whereas the 59 remaining sequences were assigned to two new clades named G1 and G2, each one including sequences recently obtained from chlamydiae detected in Swedish wetland birds. G1 (18 samples from Anatidae and Rallidae) grouped closely together with genotype 1V and in relative proximity to several C. abortus isolates, and G2 (41 samples from Anatidae and Corvidae) grouped closely to C. psittaci strains of the classical ABE cluster, Matt116 and M56. Finally, deep molecular analysis of four representative isolates of genotypes 1V, G1 and G2 based on 16S rRNA, IGS and partial 23S rRNA sequences as well as MLST clearly classify these isolates within the C. abortus species. Consequently, we propose an expansion of the C. abortus species to include not only the classical isolates of mammalian origin, but also avian isolates so far referred to as atypical C. psittaci or C. psittaci/C. abortus intermediates.

Q fever is a worldwide zoonotic disease reported in humans and many animal species including cattle. The aims of this study were to evaluate the prevalence of Coxiella (C.) burnetii shedding in Polish dairy cattle herds and to identify the pathogen’s genotypes and sequence types (STs) using multiple-locus variable number tandem repeat analysis (MLVA) and multispacer sequence typing (MST) methods. The presence of C. burnetii DNA was detected using a commercial real-time PCR kit, targeting the IS1111 element. Overall, 1,439 samples from 279 herds were tested including: 897 individual milk specimens, 101 bulk tank milk samples, 409 genital tract swabs and 32 placentas. Furthermore, 30 consumer milk samples, including 10 from vending machines and 77 dairy products were also analyzed. C. burnetii shedding was confirmed in 31.54% of tested cattle herds as well as in 69.16% of consumer milk and dairy products. Among real-time PCR–positive samples, 49 specimens obtained from 49 cattle herds and 8 samples of purchased dairy products were selected for genotyping. Overall, five previously known MLVA genotypes (I, J, BG, BE, and NM) and three new ones (proposed as PL1, PL2, and PL3) were identified. Two MST sequence types were recorded: ST16 and a novel sequence (ST61). The new genotypes and sequence types need further research particularly into their pathogenicity to humans.

Coxiella burnetii is the etiological agent of Q fever, and outbreaks of Q fever have been reported in different parts of Europe both in animals and humans. Human infections are mostly associated with infections in ruminants, e.g., sheep, goats, and cows. Various professional groups are occupationally exposed to infection with C. burnetii. The aim of this study was investigate the prevalence of C. burnetii in farm workers. Serum samples were collected from 151 persons from six different regions of Poland. The serum samples were tested using three serological methods--complement fixation test (CFT), enzyme-linked immunosorbent assay (ELISA), and indirect fluorescent antibody (IFA). A total of 71 samples of blood were also tested by real-time PCR. The results showed that antibodies against C. burnetii were present in the tested sera. Average percentages of seropositive samples in IFA, ELISA, and CFT were 31.12%, 39.07%, and 15.23%, respectively. Positive results were noted in each testing center. Of the three test types, IFA results were considered the most sensitive. Real-time PCR confirmed the presence of DNA specific for C. burnetii in 10 patients. The farming workforce constitutes an occupational risk group with an increased risk for C. burnetii infection, presumably because of their contact with infected livestock.

A variety of Chlamydia species belonging to the Chlamydiaceae family have been reported in reptilian hosts but scarce data about their occurrence in turtles and tortoises are available. In this study, research was conducted to acquire information on invasive alien species (IAS) of turtles and indigenous turtles and tortoises, living both free and in captivity, as possible reservoirs of Chlamydiaceae. Analysis of specimens (pharyngeal and cloacal swabs and tissues) from 204 turtles and tortoises revealed an overall Chlamydiaceae prevalence of 18.3% and 28.6% among free-living and captive animals respectively, with variable levels of shedding. Further testing conducted with a species-specific real-time PCR and microarray test was unsuccessful. Subsequently sequencing was applied to genotype the Chlamydiaceae-positive samples. Almost the full lengths of the 16S rRNA and ompA genes as well as the 16S-23S intergenic spacer (IGS) and 23S rRNA domain I were obtained for 14, 20 and 8 specimens respectively. Phylogenetic analysis of 16S rRNA amplicons revealed two distinct branches. Group 1 (10 specimens), specific to freshwater turtles and reported here for the first time, was most closely related to Chlamydia (C.) pneumoniae strains and the newly described Candidatus C. sanzinia. Group 2 (four specimens), detected in Testudo spp. samples, showed highest homology to C. pecorum strains but formed a separate sub-branch. Finally, molecular analysis conducted on positive samples together with their geographical distribution in places distant from each other strongly suggest that Group 1 specimens correspond to a new species in the Chlamydiaceae family. In-depth studies of Chlamydia spp. from turtles and tortoises are needed to further characterise these atypical strains and address arising questions about their pathogenicity and zoonotic potential.

This review presents recent data about avian chlamydiosis. Chlamydia psittaci has been considered to be the main causative agent of chlamydiosis in birds; however, two new Chlamydia species have been detected recently— C. gallinacea in breeding birds and C. avium in wild birds. We discuss the zoonotic potential of avian Chlamydia species.