Equine herpesvirus 2 (EHV-2) infection in thoroughbred horses in Argentina

A serological study on 153 thoroughbred racing horses confirmed the presence of EHV-2 in the Argentinean equine population. A virus neutralization test showed a total of 79.7 % animals were sero-positive for EHV-2. An increase in antibodies titre with age as well as infection at earlier ages were observed.EHV-2 was isolated from 2 out of 22 nasal swabs from horses showing respiratory symptoms. The virus grew slowly and showed characteristic cytopathic effect after several blind passages on RK13 cells. The identity of the isolates was confirmed by nested PCR and restriction enzyme assay (REA).This is the first report on the presence of EHV-2 in Argentina and adds new data to the virus distribution map. Though EHV-2 was isolated from foals showing respiratory symptoms, further studies are needed to unequivocally associate this virus with clinical symptoms.Equine herpesvirus 2 (EHV-2) is a slowly growing, cell-associated gamma-herpesvirus. This virus is widespread throughout the equine population and has been isolated from horses of different countries like United Kingdom [1], Japan [2], Australia [3], New Zealand [4], Switzerland [5], Germany [6,7], United States [8,9], Canada [10], Hungary [11] and more recently, from Poland [12]. Although its role as a pathogen is controversial, some authors have reported its association with upper respiratory tract disease, inappetance, lymphadenopathy, immunosuppression, keratoconjunctivitis, general malaise and poor performance [8,13,7,16].Equine Influenza Virus and Equine Herpesvirus 4 (EHV-4) are the most common viral agents related to respiratory disease in Argentina (Dr. Barrandeguy, personal communication). These and other respiratory viruses as Adenovirus, Equine herpesvirus 1 (EHV-1), Arteritis Virus and Rhinovirus, are usually checked in the diagnostic routine of our laboratory but no records about EHV-2 isolation or frequency of sero-positive samples were available.The purpose of the present study was to analyse the pres