Seroprevalence of Equine Herpesvirus 1 (EHV-1) and Equine Herpesvirus 4 (EHV-4) in the Northern Moroccan Horse Populations

Zineb El Brini,Farid Amraoui,Hanane El Ouadi,Ouafaa Fassi Fihri,Mohammed Piro,Hassan Alyakine,Mohamed Dehhaoui,Chafiqa Lotfi,Barbara Colitti,Romain Paillot

doi:10.3390/ani11102851

Abstract

This study reports the first equine herpesvirus-1 (EHV-1) and equine herpesvirus-4 (EHV-4) seroprevalence investigation in horse populations of Morocco in 24 years. It also aims to determine antibody titers in horses vaccinated under field conditions with a monovalent EHV-1 vaccine. Blood samples were collected from 405 horses, including 163 unvaccinated and 242 vaccinated animals. They were tested using a commercial type-specific enzyme-linked immunosorbent assay (ELISA) and a virus neutralization test (VNT). Overall, 12.8% unvaccinated, and 21.8% vaccinated horses were positive for EHV-1. All samples were positive for EHV-4 when tested with the type-specific ELISA. In the vaccinated group, the VNT revealed a mean antibody titer of 1:49 for EHV-1 and 1:45 for EHV-4. The present study demonstrates that EHV-1 and EHV-4 are endemic in the horse populations in the north of Morocco, with prevalence differences between regions. Furthermore, horses vaccinated with a monovalent EHV-1 vaccine had low antibodies titers. This study highlights the necessity to establish and/or support efficient biosecurity strategies based on sound management of horses and characterize further and potentially improve the efficiency of the EHV vaccines and vaccination protocol used in the field.

Highlights

Equine herpesvirus 1 (EHV-1) and 4 (EHV-4) are common equine pathogens [1], causing significant economic losses and a negative impact on equine welfare [2]
The EHV-1 and equine herpesvirus-4 (EHV-4) virus neutralization test (VNT) were performed for samples from unvaccinated and vaccinated horses based on the enzyme-linked immunosorbent assay (ELISA) results (Table S2) as described below: Unvaccinated group: The results showed that 90.5% of EHV-1 ELISA positive sera were positive by VNT, with a mean antibody titer of 1:26 (4–95), while 53.6% (37/69) of the EHV-1 ELISA negative sera were positive by VNT with a mean antibody titer of 1:9 (4–24)
Our results suggest that the commercial type-specific ELISA could not reliably detect the antibody response produced by the EHV-1 vaccines used in Morocco

Summary

Introduction

Equine herpesvirus 1 (EHV-1) and 4 (EHV-4) are common equine pathogens [1], causing significant economic losses and a negative impact on equine welfare [2]. EHV-1 is associated with respiratory disease, abortion, neonate death, and equine herpesvirus myeloencephalopathy (EHM) [4], whereas EHV-4 is mainly related to respiratory disease, but can sporadically cause abortions [5]. The primary infection occurs through the upper respiratory tract by direct contact with respiratory secretions of actively infected horses, aborted fetuses, or placenta [6]. The virus establishes life-long latency (estimated to concern more than 80% of the cases), and reactivation can occur under natural conditions following transport, handling, postpartum period, or experimentally by treating horses with corticosteroids [2,7]. Virus shedding could occur after reactivation from latency with a risk of spreading to susceptible animals

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