Venereal Shedding of Equid Herpesvirus-1 (EHV-1) in Naturally Infected Stallions

Background: Equid herpesvirus 1 (EHV-1) is a highly prevalent pathogen in horse populations worldwide. Oronasal infection represents the classic route of disease transmission. Venereal shedding of EHV-1 is not regarded relevant in terms of virus spreading, which is in contrast to the close relatives of EHV-1, bovine and suid alphaherpesvirus, for which artificial insemination is a well-documented and accepted means of virus spread. 
Objectives: Documentation of venereal EHV-1 shedding in 3 naturally infected stallions. 
Animals: Three stallions were infected during an acute outbreak by an EHV-1 strain with the G₂₂₅₄/D₇₅₂ Pol genotype. 
Methods: In this observational study, 12 semen samples from these 3 stallions were tested for EHV-1 to determine venereal shedding. EHV-1 was diagnosed by conventional PCR and paired serum neutralization tests in 42 horses. Semen samples were separated into sperm and seminal plasma fractions and tested for EHV-1 by conventional and quantitative PCR as well as virus isolation by cell culture. 
Results: Acute EHV-1 infection was diagnosed on the premise. Five semen samples collected from 2 of the 3 stallions tested positive for EHV-1 by (q)PCR. On days 18 and 20 after onset of fever, the last positive samples were retrieved. All samples were positive in seminal plasma, only three in sperm fraction. Virus isolation attempts were unsuccessful. 
Conclusions and Clinical Importance: The data presented here document shedding of EHV-1 in semen of naturally infected stallions for close to 3 weeks, which seems not to be directly associated with spermatozoa. © 2012 by the American College of Veterinary Internal Medicine.