Frequency of Detection of Respiratory Pathogens in Nasal Secretions From Healthy Sport Horses Attending a Spring Show in California.

This study offers insight into the frequency of certain respiratory pathogens found in nasal secretions and stall swabs from healthy sport horses during a spring show in California. It highlights the role of subclinical shedders in potentially spreading these pathogens and underlines the need for improved cleanliness and disinfection practices.

Study Objective and Methodology

• The primary aim of this research was to determine the detection frequency of various respiratory viruses like equine influenza virus (EIV), multiple strains of equine herpesvirus (EHV-1, EHV-2, EHV-4, and EHV-5), equine rhinitis A and B viruses (ERAV and ERBV), as well as bacteria like Streptococcus equi ss. equi (S. equi) and S. equi ss. zooepidemicus (S. zooepidemicus).
• This investigation involved 162 nasal secretions and 149 stall swabs collected from healthy sports horses present at a spring show in California.
• The collection procedure occurred only once, and the samples were analyzed later via quantitative PCR (qPCR), a laboratory technique used to amplify and concurrently quantify a targeted DNA molecule.

Results and Findings

• Among nasal secretions, EHV-2 was detected in 38.9% of the samples, EHV-5 in 36.4%, S. zooepidemicus in 19.7%, ERBV in 1.2%, and S. equi in 0.6%. No instances of EIV, EHV-1, EHV-4, or ERAV were detected.
• In the cases of the stall swabs, S. zooepidemicus was found in 65.8% of the samples, EHV-2 in 33.5%, EHV-5 in 27.5%, EHV-1 in 3.3%, and EHV-4 in 1.3%. The pathogens EIV, ERAV, ERBV, and S. equi were not found at all.
• Notably, the study found a high frequency of commensal (i.e., non-harmful) viruses and bacteria in both nasal secretions and stall swabs of healthy sport horses. This contrasted sharply with a much lower presence of known respiratory pathogens, implying that these horses can be subclinical shedders of these pathogens.
• Interestingly, five of the stalls had EHV-1 qPCR-positive results. These belonged to apparently healthy horses, with no observed clinical spread.

Implications and Conclusions

• The findings of this study underscore the potential role of subclinical shedders—animals that carry and can spread disease while appearing healthy—in introducing respiratory pathogens during shows.
• Furthermore, they also highlight the need for improved cleanliness and disinfection measures especially for the stalls used by performance horses during shows to prevent environmental contamination.