Investigation of the frequency and selected prevalence factors of equid alphaherpesvirus 4 viremia in horses with acute onset of fever and respiratory signs.
Abstract: Equid alphaherpesvirus 4 (EqAHV4; Orthoherpesviridae, Varicellovirus equidalpha4; equine rhinopneumonitis virus) has seldom been associated with complications such as abortion and myeloencephalopathy, given the low tendency of this virus to induce viremia. We investigated the frequency of EqAHV4 viremia in horses with fever and respiratory signs. Case selection included all equids with EqAHV4 quantitative real-time PCR (qPCR)-positive nasal secretions (defined as EqAHV4 qPCR-positive cases) submitted to a diagnostic laboratory. Controls consisted of each case submitted before and after each EqAHV4 qPCR-positive case. Purified nucleic acid from blood samples collected from EqAHV4 qPCR-positive horses and control cases was tested for EqAHV4 by qPCR. We selected 183 EqAHV4 qPCR-positive horses and 376 EqAHV4 qPCR-negative horses. In general, EqAHV4 qPCR-positive horses were younger, and had a lower rate of anorexia and a higher rate of nasal discharge compared to the EqAHV4 qPCR-negative horses. A total of 25 of 183 (13.7%) horses with EqAHV4 qPCR-positive nasal secretions tested qPCR-positive for EqAHV4 in blood. EqAHV4 viremic horses were significantly younger (p < 0.015 for group <1-y-old) and had a significantly higher occurrence of distal limb edema (p < 0.05) than EqAHV4 non-viremic horses. Our data support the observation that EqAHV4 viremia is rarely detected in EqAHV4-infected horses, which explains the low level of reported complications, such as abortion and myeloencephalopathy.
Publication Date: 2025-01-28 PubMed ID: 39876028PubMed Central: PMC11775911DOI: 10.1177/10406387241308080Google Scholar: Lookup
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- Journal Article
Summary
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The study was focused on understanding the frequency and factors of equid alphaherpesvirus 4 (EqAHV4) viremia, which typically does not often result in complications, in horses with fever and respiratory issues. The research found that the virus is rarely detected in the blood of infected horses, aiding to explain the low complication rate.
Research Overview
The researchers studied the occurrence rate of EqAHV4 viremia (presence of EqAHV4 in the blood) in horses that showed symptoms of fever and respiratory problems. Even though EqAHV4 usually does not lead to severe complications like abortion or myeloencephalopathy (disease affecting the spinal cord and brain), the aim was to understand the causes of this rarity.
- The sample size for the study comprised of all EqAHV4 qPCR-positive equids submitted to a diagnostic laboratory plus respective cases submitted before and after each EqAHV4 qPCR-positive case to serve as controls.
- The chosen cases included 183 EqAHV4 qPCR-positive horses and 376 EqAHV4 qPCR-negative horses.
Finding Key Observations
- In general, horses that tested positive for EqAHV4 were younger, less likely to be anorexic, and more likely to have nasal discharge versus the horses that tested qPCR-negative.
- From the 183 horses that tested qPCR positive for EqAHV4 in nasal secretions, only 25 (or 13.7%) had qPCR-positive blood tests for EqAHV4.
- The viremic (having EqAHV4 in the blood) horses were significantly younger and showed a significantly higher appearance of distal limb edema (swelling in the lower part of their limbs) compared to the non-viremic horses.
Conclusion
The findings of this study solidify the understanding that EqAHV4 viremia occurrence in infected horses is a rare phenomenon. This sparsity of the virus in the blood effectively explains why serious complications (abortion, myeloencephalopathy) associated with this virus infestation are not commonly seen in horses.
Cite This Article
APA
Pusterla N, Barnum S, Lawton K, Craig B, James K.
(2025).
Investigation of the frequency and selected prevalence factors of equid alphaherpesvirus 4 viremia in horses with acute onset of fever and respiratory signs.
J Vet Diagn Invest, 37(2), 349-353.
https://doi.org/10.1177/10406387241308080 Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
- Merck Animal Health, Madison, NJ, USA.
- Department of Obstetrics, Gynecology and Reproductive Biology, Massachusetts General Hospital, Boston, MA, USA.
MeSH Terms
- Animals
- Horses
- Horse Diseases / virology
- Horse Diseases / epidemiology
- Viremia / veterinary
- Viremia / virology
- Viremia / epidemiology
- Herpesviridae Infections / veterinary
- Herpesviridae Infections / virology
- Herpesviridae Infections / epidemiology
- Female
- Prevalence
- Fever / veterinary
- Fever / virology
- Male
- Real-Time Polymerase Chain Reaction / veterinary
- Varicellovirus / isolation & purification
Conflict of Interest Statement
Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
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