Metagenomics for Pathogen Detection During a Mass Mortality Event in Songbirds

Area of Science:

• Veterinary Pathology
• Wildlife Health
• Microbiology

Background:

• Mass mortality events in wildlife populations can indicate emerging infectious diseases.
• Hundreds of dead passerine birds were reported across the eastern US in 2021, exhibiting neurological and ocular signs.

Purpose of the Study:

• To investigate the cause of a mass mortality event in passerine birds in the eastern US.
• To evaluate the utility of high-throughput metagenomic next-generation sequencing in diagnosing wildlife disease outbreaks.

Main Methods:

• High-throughput metagenomic next-generation sequencing was performed on samples from affected and unaffected birds across three laboratories.
• Clinical signs and diagnostic findings were analyzed to identify potential causative agents.

Main Results:

• Metagenomic analysis detected numerous potentially pathogenic microbes, primarily bacteria, but no single agent was consistently identified in affected birds.
• Many detected microbes were also present in unaffected control birds, indicating subclinical infections or commensal relationships.
• Consistent results across laboratories supported further investigation into non-infectious causes like environmental contaminants or nutritional deficiencies.

Conclusions:

• Metagenomic sequencing is a valuable tool for investigating wildlife mortality events, even when a single infectious agent is not identified.
• The study provides a framework for future investigations into emerging wildlife diseases and highlights the need to consider multifactorial causes.