# Long-Term Surveillance of Chlamydia psittaci and West Nile Virus in Wild Birds from Central Spain (2013–2022)

## TL;DR

This study monitored Chlamydia psittaci and West Nile Virus in wild birds in Spain from 2013 to 2022, finding low pathogen presence and highlighting the need for continued surveillance.

## Contribution

The study provides a nine-year passive surveillance dataset on two zoonotic pathogens in wild birds using a wildlife rehabilitation center in central Spain.

## Key findings

- Only one bird tested positive for Chlamydia psittaci in 2021, with a positivity rate of 0.22%.
- No West Nile Virus cases were detected in any of the 1024 samples tested over nine years.
- Low detection rates may reflect limited pathogen circulation or surveillance variability.

## Abstract

Wild birds are relevant reservoirs and sentinels for zoonotic pathogens such as Chlamydia psittaci and West Nile virus (WNV), both of which can affect animal and public health. Wildlife rehabilitation centers (WRCs) offer unique opportunities for passive surveillance of emerging and re-emerging infectious diseases, particularly in urban and peri-urban settings. From 2013 to 2022, a total of 1024 bird samples were collected upon admission to WRCs in the Community of Madrid, Spain. Oropharyngeal and cloacal swabs, as well as tissue samples, were tested using real-time PCR targeting the ompA gene of C. psittaci and the 3’NC region of WNV. One sample tested positive for C. psittaci by real-time PCR in 2021, yielding a positivity rate of 0.22% (95% CI: 0.01–1.19). No positive cases were detected during the remaining years of the study. All samples tested negative for WNV over the nine-year period. The low detection rate suggests limited circulation of these pathogens among wild birds in central Spain, though it may partly reflect the variability inherent to passive surveillance and sample-type heterogeneity. However, continued surveillance is warranted, especially in high-risk avian species and personnel occupationally exposed in avian rehabilitation facilities using expanded sample sizes and complementary diagnostic tools. Extending monitoring beyond the typical vector season and increasing testing of sensitive tissues, particularly for WNV, may further enhance detection sensitivity and strengthen early-warning capacity. These efforts are essential to improve early detection and risk assessment within a One Health framework.