Molecular detection of pathogens in an equine fever diagnostic panel: 2019-2023.
Authors: Pinn-Woodcock Toby L, Aprea Melissa S, Lejeune Manigandan, Tomlinson Joy E
Journal: Equine veterinary journal
Summary
# Equine Fever Diagnostic Panel: What's Actually Being Found in Febrile Cases? Between 2019 and 2023, a newly developed equine fever diagnostic panel (EFDP) detected one or more pathogens in 38% of 961 febrile cases submitted to a US diagnostic laboratory, with *Anaplasma phagocytophilum* and beta coronavirus emerging as the most frequently identified agents. The panel utilised PCR testing on whole blood, nasal swabs, and faecal samples to screen for 12 pathogens capable of causing fever without obvious localising signs, identifying co-infections in 13% of positive cases and uncovering *Salmonella* in 22% of cases where additional culture testing was performed. Approximately two-thirds of submissions yielded no identifiable pathogen on the initial panel, highlighting the diagnostic challenge posed by equine fever cases and suggesting that other agents or non-infectious causes remain important considerations. The findings prompted the authors to expand the panel to include additional *Potomac Horse Fever* testing on faecal samples (beyond blood testing) and *Salmonella* culture, modifications implemented from November 2024 onwards. For equine practitioners, this work underscores the value of comprehensive diagnostic panels in febrile cases whilst demonstrating that negative results remain common and require thoughtful clinical interpretation alongside physical examination findings and risk factors.
Read the full abstract on PubMed
Practical Takeaways
- •When a febrile horse lacks localising signs, the EFDP can identify a causative pathogen in approximately one-third of cases, helping guide treatment decisions
- •Be aware that co-infections occur in ~13% of positive panels, which may complicate clinical presentation and require broader antimicrobial coverage
- •Potomac Horse Fever testing should now include faecal samples in addition to blood, and Salmonella culture should be considered for febrile cases, particularly in northeastern US populations
Key Findings
- •One or more pathogens were identified in 366/961 (38%) of febrile horses submitted to the panel
- •Anaplasma phagocytophilum and beta coronavirus were the most commonly detected pathogens
- •Co-infections with 2-3 pathogens occurred in 48/366 (13%) of positive cases
- •Ancillary Salmonella culture detected infection in 5/23 (22%) submissions, prompting addition to the panel as of November 2024