The researchers reported that using less invasive swabs around the muzzle/nose area of horses was effective in identifying HSV-1 infection when compared to less comfortable nasal swabs.
Swabs taken in the US study, reported in the journal Pathogensall of them were subjected to a quantitative molecular-dependent polymerase chain reaction (qPCR) assay.
Researchers at the Steinbeck Peninsula Equine Clinics and School of Veterinary Medicine at the University of California, Davis, wanted to explore sampling options for a reliable and more logistically feasible protocol during a large outbreak of EHV-1.
Outbreaks of EHV-1 usually involve mild respiratory illness associated with fever, primarily in horses under two years of age, although it can also cause miscarriage or neurological disease, Danielle Price and fellow researchers said.
Several recent EHV-1 outbreaks that have led to neurological disease support the observation that morbidity and mortality rates during outbreaks are higher than in the past.
Recent outbreaks at national and international equine shows have demonstrated the complexity of managing such outbreaks and preventing the inevitable outcome of a neurological disease, known as herpes-1 myelopathy (EHM).
Collection of whole blood and respiratory secretions from clinically ill horses for molecular testing of the virus is a gold standard for diagnosis, but contact testing, or repeated specimen collection from infected horses, is sometimes difficult to justify, mostly because of the owners’ perception that nasal swabs are invasive and cause temporary discomfort.
Also, animal health professionals involved in the response to these recent outbreaks emphasized the need to improve knowledge about the disease through systematic collection of data for analysis.
The authors note that “With increasing concerns about EHV-1 neurodegenerative disease, many horse showrooms are struggling to establish compatible protocols that reduce the risk of transmission.”
Updated EHV-1 vaccine protocols, increased awareness about biosecurity, daily physical monitoring, and pre-show testing are all measures that have been suggested or used during active outbreaks involving neurological disease.
The animals enrolled in their study consisted of show horses and pleasure horses from a large indoor facility that experienced an outbreak of the neurologically problematic EHV-1 virus as early as 2022.
In all, there were 32 adult horses of different breeds, ranging in age from 4 to 27. Initially, 19 horses made up the healthy group, but four horses ended up in the EHV-1 clinical group as they showed clinical signs.
A total of 17 horses were diagnosed with EHV-1 infection based on the presence of fever, respiratory signs, swelling of the distal extremities or fever and acute onset of neurological deficit – the latter affecting five horses.
Each horse was sampled two to four times at intervals of two to six days during the outbreak using rayon-tipped swabs. Nasal secretions were used as the preferred diagnostic sample.
Additional swab samples were taken for testing, from the muzzle/nose area, forelimbs, rectum, feeding box and troughs.
All swabs were tested for the presence of EHV-1 by qPCR.
The study team reported that, compared to nasal swabs, muzzle swabs showed good overall agreement in detecting EHV-1 in horses with clinical disease.
They concluded that non-invasive swabs from the muzzle/nose area enable identification of EHV-1 sheds during outbreaks, allowing immediate isolation and implementation of biosecurity measures.
The study team consisted of Price and Jenny Mays, with Steinbeck Peninsula Equine Clinics in Menlo Park, California. and Samantha Barnum and Nicola Bustierla, MD, of the Department of Medicine and Epidemiology at the University of California, Davis College of Veterinary Medicine.
price d. Barnum, S.; Miz, J.; Pusterla, N. Investigation of the use of non-invasive specimens for molecular detection of EHV-1 in horses with and without clinical infection. Pathogens 2022, 11, 574. https://doi.org/10.3390/pathogens11050574
The study published under CC licensecan be read here.