Original Research PaperDecreased Virus-Neutralizing Antibodies Against Equine Herpesvirus type 1 In Nasal Secretions of Horses After 12-hour Transportation
Introduction
Equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4) are causative agents of respiratory illnesses especially in young horses [1]. Initial infection typically occurs in foals, and horses are repeatedly infected with these viruses throughout life. Both viruses cause similar respiratory disease that causes economical losses through lost days in training and withdrawal of affected horses from races or events [2]. In addition, EHV-1 infections are associated with neurologic disease and abortion, resulting in significant damage to horse industries [1]. Both viruses establish latent infection in >60% of animals [3], [4], [5]. The site of latency remains controversial: While some studies showed latency occurs in circulating lymphocytes or lymph nodes [5,6], other studies have demonstrated latent virus in sensory nerve cell bodies within the trigeminal ganglia [7,8]. Reactivation of latent viruses is thought to occur when the host immune system is compromised [8]. The mechanism of the reactivation process is still unclear. A small fraction of lymphocytes carrying the latent EHV-1 genome can progress toward active transcription resulting in DNA revival and fusogenic viral glycoprotein expression on their cell surfaces ultimately leading to active virus replication [3,8]. Reactivation of latent virus leads to virus shedding in the nasal mucosa, which enables virus propagation and disease spread among horse population.
Vaccination partially protects horses from EHV-1-induced disease [9]. Both humoral and cell-mediated immunity are regarded as essential in protection against these viruses [1,10]. Additionally, mucosal immunity is considered to play a crucial role in protection, because the nasal mucosa is the primary replication site for EHV-1 after infection and soon after reactivation of latent virus [11]. Recent studies showed that the presence of virus-specific antibodies in nasal secretions in horses vaccinated with modified live EHV-1 vaccine was associated with protective effect after viral challenge [12,13].
Reactivation of latent EHV-1 and EHV-4 and subsequent disease outbreaks have been associated with horse sales, shows or events [8,14]. Previous reports monitoring EHV-1 and EHV-4 infection during such events showed virus shedding or seroconversion rates ranging from 2.6 to 3.8% for EHV-1 and 1.1 to 14.4% for EHV-4 [15], [16], [17], [18]. Transportation has been proposed as a stressor leading to EHV-1 or EHV-4 associated disease, either due to primary EHV-1 infection or viral reactivation from latency sites during the comingling of horses, and possibly in conjunction with other associated factors such as rehousing, strenuous exercise or other management changes [8,14]. Long distance transportation causes acute stress in horses, leading to physiological changes including alteration of immune responses [19,20]. Previous reports on immune modulation in horses after transportation have focused mainly on lymphocyte composition and proliferative activity, showing increased neutrophil/lymphocyte ratio and a decreased rate of mitogen induced lymphocyte proliferation after transportation [19,20]. Other studies have evaluated changes to innate immunity and mucosiliary clearance as contributing to transportation-associated bacterial pleuropneumonia [21,22]. In contrast, the possible association of transport stress with the immunity against specific pathogens such as EHV-1 and EHV-4 has not been studied well. The objective of the present study was, therefore, to assess whether 12-hour transportation of horses was associated with replication of EHV-1 or EHV-4 or, by serial measurement of serum and mucosal antibodies, with altered systemic, or mucosal immunity against EHV-1 and EHV-4.
Section snippets
Horses
Six Thoroughbred horses (2–6-year-old [mean, 3.5], three geldings and three females) were used. Horses were free of clinical disease and had prior experience of transportation. Serum samples collected from the horses approximately one month before transportation were tested for antibodies against EHV-1 and EHV-4 using glycoprotein E1-enzyme-linked immunosorbent assay (gE1-ELISA) for EHV-1 and glycoprotein G4-ELISA (gG4-ELISA) for EHV-4, respectively, as described previously [23,24]. These
Results
All horses travelled well and clinical examinations did not show any signs of illness during or after the transportation, and no horse had a rectal temperature ≥38.5°C.
Discussion
The observed increase in plasma cortisol concentration suggested that the horses were under acute stress due to transportation, as expected, although no evidence for active replication of EHV-1 or EHV-4 after transportation was observed in the current study by real-time PCR, increased ELISA titer, or clinical assessment. Transiently decreased VN titers against EHV-1 were observed in nasal secretions after transport. Suppressed mucosal VN titers might be permissive for EHV-1 replication in the
Conclusions
Twelve hours transportation caused acute stress in horses, although replication, or lytic infection with EHV-1 and EHV-4 was not observed. VN antibody titers against EHV-1 in nasal secretions decreased transiently after transportation, while systemic humoral immunity did not change. Suppressed VN capacity against EHV-1 in the nasal mucosa may be permissive for EHV-1 replication after transportation. Further studies are required to better characterize the mechanism that potentially triggers
Data availability
The datasets generated during the current study are available from the corresponding author on reasonable request.
Acknowledgments
We thank Dr. Masayuki Yamada and Dr. Yohei Minamijima at the Laboratory of Racing Chemistry for the measurement of plasma cortisol concentration. We also thank Akira Kokubun, Miwa Tanaka, Akiko Kasagawa, Akiko Suganuma, Kaoru Watanabe and Kayo Iino at the JRA's Equine Research Institute for their technical assistance. Special thanks to Dr. Kazuhisa Hariu at the JRA's Racing Museum for assisting sample collection.
Financial disclosure
This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.
References (41)
- et al.
Equine herpesviruses 1 (EHV-1) and 4 (EHV-4)–epidemiology, disease and immunoprophylaxis: a brief review
Vet J
(2005) - et al.
The equine immune response to equine herpesvirus-1: the virus and its vaccines
Vet Immunol Immunopathol
(2006) - et al.
Comparison of protective efficacies between intranasal and intramuscular vaccination of horses with a modified live equine herpesvirus type-1 vaccine
Vet Microbiol
(2018) - et al.
Intranasal IgG4/7 antibody responses protect horses against equid herpesvirus-1 (EHV-1) infection including nasal virus shedding and cell-associated viremia
Virology
(2019) - et al.
Equine viral respiratory pathogen surveillance at horse shows and sales
J Equine Vet Sci
(2013) - et al.
Immunological, clinical, haematological and oxidative responses to long distance transportation in horses
Res Vet Sci
(2017) - et al.
Identification of a major immunogenic region of equine herpesvirus-1 glycoprotein E and its application to enzyme-linked immunosorbent assay
Vet Microbiol
(2013) - et al.
Multiplex real-time PCR for the detection and differentiation of equid herpesvirus 1 (EHV-1) and equid herpesvirus 4 (EHV-4)
Vet Microbiol
(2007) - et al.
Comparison of the efficacy of inactivated combination and modified-live virus vaccines against challenge infection with neuropathogenic equine herpesvirus type 1 (EHV-1)
Vaccine
(2006) - et al.
Lack of virulence of the murine fibroblast adapted strain, Kentucky A (KyA), of equine herpesvirus type 1 (EHV-1) in young horses
Vet Microbiol
(1996)
Estimation of nasal epithelial lining fluid using urea as a marker
J Allergy Clin Immunol
Parenteral nutrition maintains pulmonary IgA antibody transport capacity, but not active transport, following injury
Am J Surg
Nasal IgA secretion in a murine model of acute stress. The possible role of catecholamines
J Neuroimmunol
Successful control of winter pyrexias caused by equine herpesvirus type 1 in Japanese training centers by achieving high vaccination coverage
Clin Vaccine Immunol
Experimental reactivation of equid herpesvirus 1 (EHV) following the administration of corticosteroids
Equine Vet J
The prevalence of latent equid herpesviruses in the tissues of 40 abattoir horses
Equine Vet J
Latent equid herpesviruses 1 and 4: detection and distinction using the polymerase chain reaction and co-cultivation from lymphoid tissues
J Gen Virol
Detection of latency-associated transcripts of equid herpesvirus 1 in equine leukocytes but not in trigeminal ganglia
J Virol
The detection of latency-associated transcripts of equine herpesvirus 1 in ganglionic neurons
J Gen Virol
The trigeminal ganglion is a location for equine herpesvirus 1 latency and reactivation in the horse
J Gen Virol
Cited by (5)
Welfare of equidae during transport
2022, EFSA JournalVaccinations in horses
2022, Praktische TierarztEffect of restraint inside the transport vehicle on heart rate and heart rate variability in Thoroughbred horses
2022, Journal of Equine Science
Conflict of interest statement: The authors declare that they have no conflicts of interest.
Ethical statement: Regarding the current submission, the authors understand the Ethical Guidelines for Journal Publication of Elsevier Publishing, and follow the policy.