Comparison of nasal swabs and handmade foam cubes for detecting equine herpesvirus 5 (EHV-5) by quantitative polymerase chain reaction (qPCR).

Overview

• This study compares two sampling methods—nasal swabs and handmade foam cubes—for detecting equine herpesvirus 5 (EHV-5) in horses using quantitative polymerase chain reaction (qPCR).
• It evaluates both the diagnostic effectiveness and the tolerability of these sampling techniques to determine if handmade foam cubes provide any advantage over the currently recommended polyester nasal swabs.

Background

• Equine respiratory infections pose significant biosecurity challenges in horse populations.
• Rapid viral detection is crucial for controlling outbreaks. Quantitative polymerase chain reaction (qPCR) is a sensitive and rapid method used for detecting respiratory viruses from nasal samples.
• Traditionally, viral culture was used, but qPCR has largely replaced this method due to speed and sensitivity.
• Some diagnostic laboratories have developed handmade foam cubes designed to collect more nasal secretions than traditional nasal swabs with the aim of improving viral detection.
• However, these handmade techniques had not been systematically compared to standard nasal swabs specifically in relation to qPCR detection of EHV-5.

Objectives

• To compare the effectiveness of nasal polyester swabs versus handmade foam cubes in detecting EHV-5 infection via qPCR.
• To assess the tolerability of each sampling method in horses, evaluating whether either method causes more discomfort or aversive behavior.

Methods

• The study sampled 9 horses, each sampled 5 times, resulting in 45 pairs of samples: one nasal swab and one foam cube per sampling event.
• Polyester nasal swabs and handmade foam cubes were used to collect nasal secretions.
• Samples were analyzed using qPCR targeting EHV-5.
• qPCR results were categorized as positive, suspect (uncertain), or negative for the presence of EHV-5 DNA.
• The agreement between the two sampling methods’ results was evaluated using the intraclass correlation coefficient (ICC), a statistical measure indicating how closely results from two methods agree.
• Tolerability was assessed by measuring avoidance behavior scores in horses for each sampling method and analyzed using a proportional odds mixed model to test for differences.

Results

• The ICC value was 0.61 with p < 0.001, indicating moderate agreement between nasal swabs and foam cubes in detecting EHV-5.
• Overall, 27% of the samples were positive or suspect on either method.
• Strictly positive detections were 18% for nasal swabs and 11% for foam cubes, showing swabs detected more definite positives.
• Avoidance scores, reflecting how well horses tolerated the sampling methods, were not statistically different between the swabs and foam cubes.
• These results suggest both methods are similarly tolerated by horses and have acceptable but not perfect agreement in diagnostic results.

Conclusions

• Handmade foam cubes do not provide added diagnostic benefit over the established polyester nasal swabs for qPCR detection of EHV-5 in horses.
• The currently recommended nasal polyester swabs remain the preferred sampling method due to at least equal detection rates and similar tolerability.
• The study supports continued use of nasal swabs for biosecurity monitoring of equine respiratory infections.

Significance

• Provides evidence-based confirmation that newer handmade sampling tools do not necessarily improve virus detection over existing methods.
• Helps laboratories prioritize resources and standardize sampling protocols by validating polyester nasal swabs as reliable for qPCR detection of EHV-5.
• Enhances understanding of sampling technique impact on diagnostic accuracy and animal welfare during infectious disease surveillance.