Investigation of the Role of Healthy and Sick Equids in the COVID-19 Pandemic through Serological and Molecular Testing.
Authors: Lawton Kaila O Y, Arthur Rick M, Moeller Benjamin C, Barnum Samantha, Pusterla Nicola
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Although horses possess the cellular machinery to support SARS-CoV-2 infection based on ACE-2 receptor homology with humans, researchers found no evidence of clinical disease in the species despite widespread human COVID-19 circulation during 2020. A large screening programme examining nasal secretions from 667 horses presenting with acute fever and respiratory signs detected zero SARS-CoV-2 cases by qPCR, whilst 36% tested positive for established equine respiratory pathogens (influenza, herpesvirus, strangles), establishing that diagnostic capacity was adequate. Serological testing of 587 racing Thoroughbreds in California with documented human exposure revealed that 5.9% had developed antibodies against the spike protein receptor-binding domain, indicating asymptomatic infection had occurred in a subset of the population. The findings suggest horses function as incidental, non-clinical hosts rather than symptomatic patients or significant reservoirs, aligning with patterns observed in companion animals. Whilst equine practitioners should be reassured that SARS-CoV-2 does not appear to cause overt respiratory disease in horses, the demonstration of silent seroconversion warrants basic biosecurity measures—particularly encouraging COVID-positive handlers and owners to minimise close contact during acute illness, thereby reducing unnecessary zoonotic spillover events.
Read the full abstract on PubMed
Practical Takeaways
- •Respiratory disease in horses is not caused by SARS-CoV-2; continue investigating other viral and bacterial pathogens in horses presenting with fever and respiratory signs
- •Some horses can become infected with SARS-CoV-2 without showing clinical signs; handlers with COVID-19 should minimize direct contact with equids to prevent asymptomatic spillover
- •Serological testing may be useful for retrospective identification of SARS-CoV-2 exposure in horse populations with known human COVID-19 cases, though most infected horses remain clinically silent
Key Findings
- •0/667 (0%) horses with acute fever and respiratory signs tested qPCR-positive for SARS-CoV-2 despite 36% testing positive for other common respiratory pathogens
- •35/587 (5.9%) healthy racing Thoroughbreds developed detectable antibodies to SARS-CoV-2 following human spillover events
- •Horses do not develop clinical SARS-CoV-2 infection but can act as incidental hosts experiencing silent infection
- •SARS-CoV-2 can spillover from infected humans to horses, similar to transmission patterns observed in dogs and cats