Bubaline herpesvirus-1 infection in Italian buffalo and potential impact on BoHV-1 eradication program

Bubaline Herpesvirus-1 (BuHV-1) belongs to the subfamily Alphaherpesvirinae, which includes as the prototype Bovine Herpesvirus-1 (BoHV-1). BuHV-1 infection in buffaloes is usually subclinical and the virus may be latent for long time. BuHV-1 has been detected in Italian buffaloes after experimental immunosuppressor treatment and some genetic characteristics have been so far described. A close similarity has been described among the DNA sequences of BoHV-1 and BuHV-1 encoding for the gB, gC and gD. However, BuHV-1 seems to be genetically more correlated to BoHV-5 than to BoHV-1. Antibodies against BoHV-5 have been previously differentiated from antibodies against BoHV-1 by a BoHV-1 gE blocking ELISA. The aim of this study was to test a gB/gE ELISA kit on bubaline sera and to evaluate the ability of the ELISA test to discriminate between BoHV-1 and BuHV-1 infected animals. The test includes two blocking ELISA directed to the BoHV-1 gB and gE which had been developed to discriminate between animals infected by BoHV-1 and animals vaccinated with a gE deleted BoHV-1 vaccine. For this purpose, sera samples collected from 681 unvaccinated buffaloes from 8 farms in Central Italy have been tested by a commercially available gB/gE ELISA test. Seroneutralization tests for BuHV-1 and BoHV-1 have been carried out on the 157 samples resulted gB positive and gE negative. The immune sera used for the seroneutralization were obtained by experimental inoculation of BuHV-1 and BoHV-1 respectively in a buffalo and in a cattle. The seroneutralization test showed antibody titres more than three times higher for BuHV-1 than for BoHV-1 in all the 157 gB+ and gE- sera, confirming the BuHV-1 infection. The results obtained in this preliminary study suggest the use of the gB/gE ELISA test for the survey of BuHV-1 infection in buffaloes in Italy. However, serological interference would be obtained if animals vaccinated with a BoHV-1 gE- vaccine are tested. Furthermore, BuHV-1 infected animals show the same gB/gE ELISA results than BoHV-1 gE- vaccinated cattle. Therefore, if cattle would be infected by BuHV-1, the serological results could interfere with the application of the Infectious Bovine Rhinotracheitis control plans in Italy.