Analyses of restriction fragment patterns (RFPs) and pathogenicity in baby mice of equine herpesvirus 1 and 4 (EHV-1 and EHV-4) strains circulating in Danish horses.

The research article examines the strains of equine herpesvirus 1 and 4 found in Danish horses, comparing them through restriction fragment pattern analysis and baby mice inoculation. The results suggest that all EHV-1 strains belong to genome type Ip and that the live vaccine Rac H, not approved for use in Denmark, has potentially been acquired from visiting horses, leading to its circulation in the local horse population.

Introduction to the Research

• The research focuses on 25 strains of equine herpesvirus 1 (EHV-1) and one strain of equine herpesvirus 4 (EHV-4) isolated from various clinical cases in Denmark.
• These strains were analyzed using restriction fragment pattern (RFP) and by inoculating baby mice.

Key Findings

• The restriction fragment pattern analysis revealed that all EHV-1 strains belonged to the genome type Ip.
• Four fetal isolates showed genomic characteristics that are considered specific markers of the attenuated strain Rac H.
• The attenuated strain Rac H is widely used as a live vaccine.
• However, the use of such vaccines against EHV-1 and EHV-4 has never been allowed in Denmark.

Implications and Conclusions

• The results of the study suggest that Rac H derivatives might have been acquired from visiting horses and are now circulating in the horse population of Denmark.
• When inoculating baby mice, four biotypes were identified based on their pathogenicity.
• However, there was no strict correlation observed between the pathogenicity in the natural host and the biotypes.

Final Thoughts

• The findings of the research present significant information about the nature of equine herpesvirus strains in Denmark, acting as a basis for further research and policy-making to regulate and manage the spread of such viruses within the horse population.