Effectiveness of a screening protocol employed at a UK rescue centre to prevent introduction of strangles.

Abstract

Background: Infection with Streptococcus equi subspecies equi (S. equi) is characterised by acute disease, with about 10% of infected animals remaining persistently infected. Clinically, infection with S. equi cannot readily be distinguished from infection caused by other respiratory pathogens, including Streptococcus equi subspecies zooepidemicus (S. zooepidemicus), equine influenza virus, and equine herpes virus. Screening protocols, with appropriate quarantining facilities, are important to detect horses infected with S. equi and avoid strangles outbreaks. Virulent strains of S. zooepidemicus can also cause strangles-like presentations.

Objectives: To evaluate the effectiveness of the screening process implemented at a UK welfare centre to prevent the introduction of strangles and strangles-like presentations.

Study design: Retrospective cross-sectional study.

Methods: Clinical records of 626 equids admitted to a UK welfare centre between 2017 and 2021 and from horses that developed respiratory signs after admission were reviewed. The screening protocol, which included a clinical examination, paired serology samples (iELISA) taken 6 weeks apart, and bilateral guttural pouch endoscopy to identify abnormalities such as chondroids with lavage for qPCR and culture analysis for S. equi (and often S. zooepidemicus) was implemented during this time.

Results: There were 34 screening-positive equids. Of these, 24 (3.8%) were qPCR-positive for S. equi, 8 were qPCR/culture positive for S. zooepidemicus, and 2 were qPCR/culture negative but had chondroids. Bilateral guttural pouch endoscopy, with qPCR analysis of lavage material, was an effective method of screening equids. There were no cases of strangles or strangles-like presentations within the main herds after screening and admission of new horses.

Main limitations: Variation in the level of detail of clinical records.

Conclusions: The screening process resulted in the identification of screening-positive equids and maintained a strangles-free herd. Further research is required to elucidate the significance of S. zooepidemicus infection in the guttural pouch.