Environmental sampling outperforms bird swabs in live poultry markets: full analysis

Environmental sampling may give veterinary and public health teams a clearer picture of what’s circulating in live poultry markets than bird swabs alone. In a new Nature Communications paper, Duke-NUS Medical School researchers and collaborators found that air, cage, and wash-water samples collected in Cambodian live poultry markets detected a wider range of poultry viruses than contemporaneous swabs from chickens and ducks, including highly pathogenic avian influenza lineages that were not always found in the birds tested at the same time. (nature.com)

The study comes as live poultry markets remain a longstanding focus of avian influenza surveillance because they bring together birds from multiple sources, creating conditions for viral amplification, reassortment, and spillover risk. Earlier work in Cambodia documented H5N1-positive environmental samples in markets as far back as 2011, while studies from Vietnam and China have shown that environmental sampling can be informative for tracking avian influenza circulation in market settings. Reviews of the field have also noted practical advantages: environmental sampling is less invasive, can face less resistance than handling birds, and may better reflect contamination across a flock or market ecosystem rather than a single point-in-time animal snapshot. (pmc.ncbi.nlm.nih.gov)

In the new study, researchers sampled two Cambodian markets between January 2022 and April 2023, collecting air from holding and slaughter areas, cage swabs, and poultry wash water, alongside chicken and duck oropharyngeal and cloacal swabs. Using targeted virus capture probe-based metagenomics, they detected 40 poultry viruses and found that environmental sampling also revealed an additional 50 viruses not seen through poultry sampling during the study period, including five additional poultry viruses. According to the paper, air from slaughter areas detected significantly more viruses than duck samples and chicken oropharyngeal swabs, and environmental samples yielded highly pathogenic influenza A contigs more often than poultry swabs. H5 clade 2.3.4.4b was identified on three market visits, but poultry swabs and environmental samples overlapped on only one of those dates; on two other visits, the clade appeared only in environmental samples. (nature.com)

The research group said the findings suggest direct animal testing is not always necessary to detect important pathogens in these settings. In the study coverage released in March 2026, first author Peter Cronin said sampling air, water, cages, and surfaces can reveal avian influenza and other poultry viruses even when those same viruses are not detected in birds at the time, while co-senior author Gavin Smith said the approach offers a more comprehensive view of viral circulation than single-animal testing alone. Those comments align with prior field studies, including a Hanoi bioaerosol study that found strong agreement between positive aerosol and swab samples and highlighted the logistical advantages of noninvasive sampling. (phys.org)

For veterinary professionals, the significance is practical as much as scientific. Surveillance systems built around bird swabs alone can underestimate what’s circulating in a market, particularly when infection is patchy, transient, or concentrated in environmental contamination rather than in the small number of birds sampled. That matters for outbreak detection, movement controls, market cleaning and disinfection, worker protection, and One Health coordination with public health partners. It also matters economically: missed circulation of highly pathogenic avian influenza can delay response in poultry supply chains and increase downstream risk for farms, processors, and even companion animals exposed through contaminated raw poultry products. USDA APHIS, for example, updated turkey surveillance policy in January 2025 after identifying a genetic link involving infected turkeys, raw pet food, and a household cat. (nature.com)

The broader industry context supports that concern. In February 2025, New York temporarily shut live bird markets in multiple counties after avian influenza detections, underscoring how quickly market findings can trigger operational and regulatory consequences. The Cambodian study does not argue that bird sampling should disappear, but it does support a layered model in which environmental sampling helps triage risk and targeted animal sampling confirms and characterizes what’s circulating. That may be especially useful in high-throughput markets where routine handling of large numbers of birds is costly, labor-intensive, or poorly accepted. (time.com)

What to watch: The next question is whether regulators and surveillance programs move from pilot and research use toward standardized environmental sampling in live poultry markets, with clear guidance on which matrices, air, wash water, cage swabs, or dust, perform best for specific pathogens and how positive findings should trigger follow-up animal testing or control measures. The evidence base is growing, but implementation will depend on cost, lab capacity, and how well metagenomic results can be translated into actionable field decisions. (nature.com)