Recrudescence of Latent Equine Herpesvirus 1 (EHV-1) in Horses after Corticosteroid Administration

Scientists in the United States have investigated the reactivation of latent EHV-1 in horses after administration of corticosteroids. This study aimed to describe the viral kinetics of reactivated EHV-1 in blood and nasal secretions from latently infected horses and to study the infectious nature of reactivated EHV-1 to sentinel horses. The researchers found that all horses in the latently infected group showed transient molecular detection of EHV-1 in blood and nasal secretions, but only one horse developed fever. Viral cultures remained negative for all latently infected horses after corticosteroid administration, and none of the sentinel horses developed clinical signs, viremia, viral shedding, or seroconversion.

Key Takeaways:

• Eight healthy horses were used in the study, with four horses latently infected with EHV-1 and four seronegative horses serving as sentinels.
• The researchers found that administration of corticosteroids led to transient molecular detection of EHV-1 in blood and nasal secretions of all latently infected horses.
• Only one horse developed fever, and there was an increase in antibody concentrations against EHV-1 in three latently infected horses.
• Viral cultures remained negative for all latently infected horses after corticosteroid administration.
• The sentinel horses did not develop any clinical signs, viremia, viral shedding, or seroconversion.
• The researchers concluded that the failure to effectively transmit EHV-1 to susceptible horses may have resulted from the low level and short period of viral shedding in latently infected horses.

Statistics:

• 8 horses were used in the study.
• 4 horses were latently infected with EHV-1 and received dexamethasone on 5 consecutive days.
• 4 seronegative horses served as sentinels and had direct contact with the latently infected horses.
• 100% of latently infected horses showed transient molecular detection of EHV-1 in blood and nasal secretions.
• 25% of latently infected horses developed an increase in antibody concentrations against EHV-1.
• 0% of sentinel horses developed clinical signs, viremia, viral shedding, or seroconversion.

Sources:

• Journal of Veterinary Internal Medicine, Molecular Investigation of the Viral Kinetics of Equine Herpesvirus-1 in Blood and Nasal Secretions of Horses after Corticosteroid-Induced Recrudescence of Latent Infection.
• University of California, Medical Department, authors N. Pusterla and colleagues.