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

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.

Respiratory and Reproductive Tract Disorders Causing Herpesviruses in Animals

“…EHV-1 also has a neurologic form in which a higher rate of morbidity and mortality is seen. Transmission of EHV-1 and EHV-4 occurs by direct or indirect contact with infectious nasal secretions, aborted fetuses, placentas, or placental fluids (El Brini et al 2021).…”

“…EHV-1 replicates in female reproductive tract and causes cell-associated viraemia that can lead to abortion. EHV-1 also causes vasculitis and thrombosis in the placenta and transplacental tissues of the foetus which also contribute in abortion (Bryant et al 2018;El Brini et al 2021).…”

“…In neurologic form of EHV-1, less apparent infection occurs, with clinical symptoms ranging from in-coordination and posterior partial or complete paralysis and recumbency (El Brini et al 2021). In neurologic form less severe ulcers or bleeding occurs in meninges, brain, and spinal cord parenchyma has also been reported.…”

Virus Infection in Equine

“…EHV-1 may cause significant economic losses due to its high morbidity and the restrictions that are required to limit its spread. In three studies published in this special issue, the authors have evaluated the exposure of different cohorts to this important pathogen [25][26][27]. African Horse Sickness should also be included in this group and although it is still limited mainly to Africa, measures should be implemented to prevent its spread, which should include active surveillance as well as preventive vaccination in neighboring countries.…”

“…Overall, 12.8% unvaccinated and 21.8% vaccinated horses were positive to EHV-1 and all were positive to EHV-4 demonstrating that both viruses are endemic in the north of Morocco, with prevalence differences between regions. Furthermore, horses vaccinated with a monovalent EHV-1 vaccine had low antibody titers, which needs to be addressed [26].…”