Chilean study compares litter-level flu sampling methods in swine
Bottom line
A new study in Animals evaluated whether litter-level sampling methods could stand in for individual pig testing when screening for influenza A virus in Chilean swine breeding herds. Researchers sampled five breeding herds in Chile from 2022 to 2024, comparing piglet oropharyngeal swabs with two group-level approaches: udder wipes collected from the sow and aggregated nasal wipes collected from piglets within the litter. According to the study abstract, 341 litters were assessed, and 26.1% of litter-level oropharyngeal swab sets were RT-qPCR positive, with the work focused on how closely the group samples agreed with that reference method. The paper adds to a growing body of work on less invasive, more practical surveillance tools for preweaning influenza A monitoring in breeding herds. (nationalhogfarmer.com)
Why it matters: For veterinarians working with swine systems, the practical question isn't just whether influenza A is present, but how to find it efficiently and consistently in farrowing rooms. Prior field research has shown that population-based samples such as udder wipes, family oral fluids, and piglet nasal wipes can improve feasibility for routine surveillance, especially when repeated sampling across rooms and litters is needed. That matters because influenza circulation in preweaning pigs can be patchy within a herd, and sample choice affects both detection probability and labor at the barn level. If this Chilean study shows strong agreement between udder wipes or aggregated nasal wipes and litter-level piglet swabs, it could support broader use of lower-burden sampling protocols in breeding-herd monitoring programs. (nationalhogfarmer.com)
What to watch: Watch for whether practitioners adopt these methods mainly for routine herd surveillance, or whether they remain a screening tool that still needs follow-up individual sampling for sequencing, subtyping, or intervention decisions. (pmc.ncbi.nlm.nih.gov)
Key facts
- Study type
- Animals study
- Species
- Chilean swine breeding herds
- Study period
- 2022 to 2024
- Herds sampled
- Five breeding herds
- Litters assessed
- 341 litters
- Reference method
- Piglet oropharyngeal swabs
- Group-level methods
- Udder wipes and aggregated nasal wipes
- Positive rate
- 26.1% of litter-level oropharyngeal swab sets were RT-qPCR positive
A new Animals study examines a question swine veterinarians deal with every week in the farrowing house: can easier, litter-level samples reliably detect influenza A virus without relying on multiple individual pig swabs? In five Chilean swine breeding herds sampled between 2022 and 2024, investigators compared RT-qPCR results from piglet oropharyngeal swabs with udder wipes and aggregated nasal wipes collected at the litter level. Based on the abstract, the study evaluated 341 litters, with 26.1% testing positive by the oropharyngeal-swab reference approach. (nationalhogfarmer.com)
The work lands in an area where surveillance methods have been evolving quickly. Influenza A remains endemic in many swine systems, and preweaning piglets are an important reservoir for continued circulation in breeding herds. Earlier modeling and field studies have linked control success to both vaccination and herd-level biosecurity, but they also underscore the need for surveillance methods that are realistic to repeat over time. (pubmed.ncbi.nlm.nih.gov)
That need has driven interest in noninvasive or population-based sampling. Previous studies from North America and Europe have assessed udder wipes, piglet nasal wipes, family oral fluids, drinker wipes, and other group samples as alternatives to individual pig sampling. In one breeding-herd field comparison summarized by National Hog Farmer, family oral fluids and udder wipes showed higher influenza A detection than piglet nasal wipes used as the reference in that study, and room-to-room variation in positivity was substantial, reinforcing the importance of broad sampling within the farrowing unit. (nationalhogfarmer.com)
Udder wipes, in particular, have gained traction because they capture secretions deposited by nursing piglets on the sow’s udder, making collection fast and less disruptive. A prior diagnostic study found that pooling udder wipe samples did not significantly reduce RT-PCR sensitivity under the tested conditions, which supports their operational appeal in surveillance programs. Other published work has also described udder wipes as an increasingly used sample type in breeding herds in North America. (pubmed.ncbi.nlm.nih.gov)
The Chilean study appears to extend that evidence base by asking not just whether these sample types can detect virus, but how closely they agree with one another at the litter level in commercial breeding herds outside North America. That geographic context matters. Sampling performance can be shaped by within-litter prevalence, infection timing, herd immunity, and management practices, so validation in different production settings helps determine whether a method is broadly useful or only context-dependent. Recent research has emphasized that detection probability varies with prevalence and sample type, especially when infection is unevenly distributed across rooms or litters. (sciencedirect.com)
Expert and industry commentary around influenza surveillance has consistently focused on the tradeoff between diagnostic sensitivity and field practicality. Swine health researchers writing for industry audiences have argued that sample selection should reflect expected within-litter prevalence and the goal of testing, whether that's routine monitoring, outbreak investigation, or generating material for further characterization. Reviews of influenza sampling methods similarly note that while less invasive specimens can improve participation and throughput, follow-up diagnostic work may still require more targeted sampling. (nationalhogfarmer.com)
Why it matters: For veterinary professionals, this isn't just a technical comparison of swabs versus wipes. It's about whether herd monitoring can become more repeatable, less labor-intensive, and still actionable. If udder wipes or aggregated nasal wipes show acceptable agreement with litter-level oropharyngeal swabs, veterinarians may be able to expand surveillance frequency, sample more litters or rooms, and get a clearer picture of influenza circulation without adding as much handling stress or labor. That could be especially useful in systems trying to track endemic circulation, assess control programs, or decide when more intensive diagnostics are warranted. (pmc.ncbi.nlm.nih.gov)
What to watch: The next step is whether this work changes on-farm sampling protocols, and whether follow-on publications provide the agreement statistics, Ct comparisons, and performance thresholds veterinarians need to choose one sample type over another in specific herd scenarios. (sciencedirect.com)