Molecular detection of pathogens in an equine fever diagnostic panel: 2019-2023.

Abstract

Background: A common diagnostic approach for febrile horses is to test for a panel of potential pathogens. Panels are curated by expert opinion and vary between diagnostic laboratories.

Objectives: To report the results of a newly developed equine fever diagnostic panel (EFDP) between 2019 and 2023 and evaluate the frequency of positive results.

Study design: Retrospective descriptive study.

Methods: The EFDP requires submission of whole blood, nasal swab, and faecal samples, and includes PCR tests for 12 pathogens that can present as fever without localising signs of illness or infection. Submission metadata and results of all submissions with EFDP performed between July 2019 and April 2023 were tabulated. Submissions were excluded if horses were <1 year old or any tests were cancelled.

Results: One or more pathogens were identified on the EFDP in 366/961 (38%) cases. The most common pathogens identified were Anaplasma phagocytophilum and beta coronavirus. Co-infections with 2 or 3 pathogens were identified in 48/366 (13%) positive panels. Ancillary testing detected Salmonella in 5/23 (22%) submissions.

Main limitations: Clinical information regarding the cases was lacking. The majority of submissions originated from the northeastern United States, and results might not be generalisable to other geographic regions.

Conclusions: The panel was able to detect a possible causative agent in approximately a third of cases. Based on the results of ancillary testing and recent literature, Potomac Horse Fever PCR on faeces (in addition to whole blood) and Salmonella culture have been added to the EFDP as of November 2024.