# Online parrot trade as a source of psittacosis caused by a novel Chlamydia psittaci ST388

## TL;DR

A human case of psittacosis in China was traced to parrots bought online, revealing a new strain of Chlamydia psittaci and highlighting risks from the digital pet trade.

## Contribution

First whole-genome confirmation of psittacosis transmission via online pet commerce and identification of a novel Chlamydia psittaci strain (ST388).

## Key findings

- 13 high-quality Chlamydia psittaci genomes were recovered from patient, parrots, and environment with >99.99% identity.
- Transmission from online-purchased parrots to human was confirmed via genomic analysis.
- A novel sequence type (ST388) within virulent genotype A was identified as the causative strain.

## Abstract

The direct zoonotic risks associated with the growing online trade of live pets remain in adequately understood.

We investigate a human case of severe psittacotic pneumonia in Zhejiang Province, China, in which the patient’s only avian exposure was through parrots recently purchased online. Using targeted probe-capture sequencing—a method designed for uncultivable, low-biomass pathogens—we recovered 13 high-quality Chlamydia psittaci genomes directly from the patient, the asymptomatic parrots, and their shared home environment.

Comparative genomic analysis revealed >99.99% average nucleotide identity across all samples, providing definitive evidence of parrot-to-human transmission. The causative strain was identified as a novel sequence type (ST388) within the known virulent genotype A.

This investigation provides the first whole-genome confirmation of psittacosis transmission via online pet commerce. It establishes a practical genomic framework for investigating similar sporadic zoonoses and underscores the urgent need for targeted surveillance of this emerging and risk communication in this growing digital marketplace.