Seroprevalence of Canine Herpesvirus-1 in Breeding Dogs with or Without Vaccination in Northwest Italy

SIMPLE SUMMARY: Canine herpesvirus-1 (CHV-1) infection during pregnancy causes foetal deaths and abortion; puppies may acquire the infection at birth from contact with vaginal and oronasal secretions of the dam and are at high risk of death. When a bitch has antibodies against the virus, her litter is safe. Antibodies are produced either following natural infection or vaccination. In this study, we wanted to assess the prevalence of antibodies in a population of breeding dogs in a region of Northwest Italy and assess the diffusion of herpesvirus vaccination. More than half of the 370 tested dogs (50.3%) were seropositive, i.e., had antibodies against CHV-1. No seropositive dogs were identified in only ten out of 33 kennels. In the vast majority of animals, antibodies resulted from natural infection since only 31 dogs had been vaccinated. More than 40% of the seropositive dogs showed high antibody titres and the number of seropositive dogs was lower in younger animals, not yet been in contact with the virus. Our data show that population immunity exists when CHV-1 is endemic. However, vaccination remains an option because seroprevalence can be highly variable and seronegative pregnant bitches will be at high risk of contracting the infection due to viral circulation. ABSTRACT: Canine herpesvirus-1 (CHV-1) can cause abortion and foetal and neonatal deaths in the bitch. The reactivation of latent infections with asymptomatic virus shedding represents a mechanism, whereby the virus can persist in a dog population. The aim of this study was to investigate the seroprevalence of CHV-1 in a population of breeding dogs in Piedmont, Northern Italy, and to investigate the distribution of herpesvirus vaccination. The study was carried out in 370 animals that were housed in 33 breeding kennels. Antibodies against CHV-1 in serum samples were measured by means of serum neutralization. Vaccination had been performed in 21.2% of the kennels and 8.4% of the dogs. The overall seroprevalence of CHV-1 was 50.3%. In ten kennels (30.3%), no seropositive dogs were identified. The percentage of seropositive dogs ranged from 7.1% to 100% in positive kennels. More than 40% of the seropositive dogs showed high titres. Sex had no significant effect on either seroprevalence or the category of the serum titre. The number of positive animals was significantly lower in the groups of prepuberal bitches and animals younger than 1.5 years. The majority of younger animals showed very high titres, suggesting recent contact with the virus. Our data show that CHV-1 is a common infection in breeding dogs in Piedmont. Vaccination is rarely performed but might be an option, because, although many animals of breeding age already show high antibody titres, seronegative pregnant bitches will be at high risk of contracting the infection due to viral circulation in kennels where the virus is enzootic.