Comparison of sampling sites and laboratory diagnostic tests for S. equi subsp. equi in horses from confirmed strangles outbreaks.

The research article focuses on improving the detection rates of Strangles, a contagious disease in horses, by sampling techniques and laboratory diagnosis methods. The study concludes that using a nasopharyngeal lavage combined with real-time PCR directly and after culture can identify the causative bacteria in over 90% of acute cases.

Research Objective

The objective of this research was to improve the identification yield of Streptococcus equi subsp. equi (S. equi) the bacteria causing the equine disease strangles. Despite advances in molecular biology methods and sampling techniques, detection of S. equi often fails in up to 40% of infected horses leading to undiagnosed and untreated cases. The research particularly aimed to compare the efficiency of different sampling methods and laboratory tests.

Research Methodology

• The study was a prospective one involving 57 horses from eight confirmed strangles outbreaks. The sampled horses represented a wide range of breeds and ages.
• The sampling involved nasal swabs, nasopharyngeal swabs, and nasopharyngeal lavages. These were subjected to real-time PCR directly, and after culture, along with biochemical identification methods.

Research Findings

• Real-time PCR performed directly on the samples identified the highest number of infected horses. Out of 57 horses, 45 nasal swabs, 41 nasopharyngeal swabs, and 48 nasopharyngeal lavages were S. equi positive.
• When compared to real-time PCR, biochemical identification produced fewer positive results regardless of the sampling method used. The highest positives from this method was 22 out of 57.
• Nasopharyngeal lavage samples analyzed by real-time PCR directly and after culture yielded S. equi in 52/57 horses. Combining direct real-time PCR of nasopharyngeal lavage with either nasopharyngeal swabs or nasal swabs increased the detection rate to 53 positive results out of 57. Only three horses were negative across all applied sampling methods.

Conclusions

The research concluded that real-time PCR combined with nasopharyngeal lavages can identify S. equi in over 90% of acute strangles cases. This suggests an improvement in detection rates can be achieved by deploying these methods. In particular, directly applying real-time PCR to a nasopharyngeal lavage and either a nasal or nasopharyngeal swab can boost the detection of S. equi infection.