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Simple Summary: This study evaluated the molecular prevalence and genetic characterization of equine EHV-1/4 in equids populations in Morocco. Among 154 samples analyzed, 27% tested positive for EHV-4, while only 1.94% were positive for EHV-1. Virus isolation was unsuccessful in EHV-4-positive samples but EHV-1 was isolated from a positive donkey sample. Phylogenetic and molecular analyses reclassified the EHV-1 isolate from the donkey as EHV-8, while the EHV-1 isolate from aborted fetal tissue was identified as clade 1 EHV-1. This study confirms the active circulation of EHV-1 and EHV-4 in Moroccan equines, reports the first detection of EHV-8 in a donkey in Africa, and highlights EHV-4′s prevalence and its association with respiratory disorders, abortions, and neonatal deaths. This study aimed to investigate the molecular prevalence and genetic characterization of EHV-1 and EHV-4 in equid populations in Morocco. A total of 154 equids (114 horses, 9 donkeys, and 31 mules) were sampled, with nasal swabs and tissue samples subjected to multiplex real-time PCR for the detection of EHV-1 and EHV-4. Additionally, an isolate from the tissue of an aborted horse fetus was included in the analysis. A subset of EHV-positive samples underwent virus isolation followed by whole-genome sequencing. PCR assays revealed that 42 samples (27%) tested positive for EHV-4, while only 3 samples (1.94%) were positive for EHV-1. Attempts to isolate the virus from EHV-4-positive samples were unsuccessful. However, virus isolation was successful in an EHV-1-positive nasopharyngeal sample from a donkey. Phylogenetic and molecular characterization reclassified the EHV-1 isolated from the donkey as an EHV-8. Meanwhile, the EHV-1 isolated from the aborted fetal tissue was classified as a clade 1 EHV-1 virus. This study is the first to report the molecular prevalence and genetic characterization of EHV-1 and EHV-4 in equid populations in Morocco, providing valuable insights into the distribution and genetic diversity of these viruses in the region. [ABSTRACT FROM AUTHOR]

Simple Summary: This work aims to evaluate the seroprevalence of equine EHV-1/4 in horse populations in the north of Morocco and to measure the antibody titers in vaccinated horses, under field conditions, with monovalent EHV-1 vaccines. 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. The virus neutralization test showed low antibody titers in samples from vaccinated horses. Our study demonstrated that EHV-1 and EHV-4 are endemic in the horse populations in the north of Morocco and highlighted the necessity of reevaluating the vaccines and the vaccination protocol used. 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. [ABSTRACT FROM AUTHOR]