Experimental studies on equine herpesvirus type 1 infections.

The article analyzes the behavior of different strains of Equine Herpesvirus (EHV-1), particularly those isolated from fetal tissues and respiratory disease samples, highlighting that fetal-derived strains are more successful in growth, transmission, and causing complications like abortion in partly immune horses.

Strains of EHV-1

• The research focused on two particular strains of the Equine Herpesvirus type 1 (EHV-1)—one obtained from horse fetuses (referred to as F/304) and the other from horses with respiratory diseases (designated as R/NM-3).
• The EHV-1 virus is a serious pathogen in horses, causing a range of symptoms from respiratory disease to abortion in pregnant mares.

Growth and Host Range

• The study found that the fetal strain (F/304) of the virus grew more effectively and had a broader tissue culture host range compared to the respiratory-disease strain (R/NM-3).
• Meaning, the F/304 strain was found to be more capable of infecting various types of cells within the horse.

Infection in Partly Immune Horses

• Upon exposure to both EHV-1 strains, horses that were partly immune were more readily infected by the fetal isolate (F/304) as opposed to the respiratory disease isolate (R/NM-3).

Influence on Abortion

• Further, it was observed that horses infected with the fetal isolate were more prone to experience abortion, demonstrating the higher pathogenicity of the F/304 strain.

Excretion into the Environment

• The research also established the fetal isolate, F/304, was excreted into the environment more extensively than the R/NM-3 strain, indicating its higher transmissibility or ability to spread.

Implications of the Study

• The markedly different behaviors of these two strains underline the importance of understanding the source of the virus when dealing with an EHV-1 outbreak.
• The higher virulence and contagiousness of the fetal strain could necessitate different treatment or prevention strategies for the infection.