Coital exanthema of horses: diagnosis and identification of the pathogen

Abstract

Comprehensive studies were performed during an acute outbreak of horses with symptoms of exanthematous lesions of the external genitalia, observed in 2018. The lesion of the external genital organs was observed in the form of puffiness of the vestibule of the vagina and vulva in mares and prepuce in stallions, formation on the mucous membrane and skin of papules, vesicles and pustules, in the last stage - ulceration and crusts on the affected areas. A fragment of the genome of equine herpesvirus type 3, the causative agent of coital exanthema, was found in scrapings from the affected areas using the methods of molecular genetic analysis. The results of the determination of nucleotide sequences showed a high degree of phylogenetic relationship with the strain «YS-1» isolated from sick horses in Japan in 2017. The homology of alignment of nucleotide sequences within the studied region of the genome ― a fragment of the gpG gene (813…1292 bp) ― was 100 %. In 90 % of the samples containing the DNA of the coital exanthema virus, DNA of the virus of rhinopneumonia-viral abortion (equine herpesvirus type 1) was also found, and only in 10 % of cases monoinfection of EHV-3 was observed. Participation in the EHV-1 infectious process was confirmed by a retrospective serological study. In NT, antibodies to EHV-1 were detected in a titer of 1: 16…1: 32. A comparative analysis of retrospective data showed that a similar outbreak of coital exanthema observed in 1980–81 was due to EHV-3 monoinfection.