A single genotype of Chlamydia psittaci (ST27) found in multiple species of birds in a zoological collection in New Zealand.

Aims: To investigate the genotypes of Chlamydia psittaci in birds associated with two clusters of disease from a zoological collection in New Zealand.

Materials and methods: Samples were collected over two time periods from birds resident at Auckland Zoo (Auckland, NZ). In 2016, two little penguins/kororā (Eudyptula minor) showed respiratory disease on admission to the zoo hospital. Post-mortem samples of liver and lung were collected from the penguins and from 10 other birds from the zoo's collection that died without clinical signs. Further, 128 conjunctival, choanal and cloacal swabs were collected from 27 different bird species, all housed within the zoo and without clinical signs.In 2019, a cluster of deaths of four diamond doves (Geopelia cuneata) and two superb parrots (Polytelis swainsonii) occurred in one mixed-species aviary. Twenty post-mortem samples were collected from these birds and other birds that died around the same time across the zoo. DNA was extracted from all samples and initially tested for C. psittaci using a high-resolution melting quantitative PCR (HRM qPCR) protocol. We applied multi-locus sequence typing (MLST) on 10 C. psittaci-positive samples from four different avian species, including one sample from 2016 (little penguin) and nine post-mortem samples from 2019.

Results: C. psittaci was detected in 14/140 (0.10; 95% CI = 0.061-0.161) of the samples from 2016 from seven species. A penguin sample was sequenced aligning with ompA genotype B and was later characterised by MLST as C. psittaci strain ST27. With the exception of the sample from the sick penguin, the positive results yielded very low DNA copy numbers in the HRM qPCR, potentially indicating latent infections. In the 2019 cluster, C. psittaci was detected in 9/20 post-mortem samples from three bird species (diamond dove, superb parrot, and zebra finch (Taeniopygia guttata)). All nine sample sequences aligned with ompA genotype B and were characterised by MLST as C. psittaci strain ST27.

Conclusions and clinical relevance: C. psittaci was present within the zoological collection in a variety of bird species associated with two disease clusters. Most of these infections were asymptomatic, but a cluster of deaths due to avian chlamydiosis in 2019 affecting three species of birds was due to a single genotype, ST27, that was also present in a wild penguin in 2016. This provides evidence of pathogenicity in birds for this genotype.

Abbreviations: C-C-C: Conjunctival, choanal slit and cloacal swabs; Cq: Cycle threshold; HRM qPCR: High resolution melting quantitative PCR; MLST: Multi-locus sequence typing; ompA: Outer membrane protein A; ST: Sequence type; WGS: Whole genome sequencing.