High prevalence of co-infections with bovine herpesvirus 1 and 5 found in cattle in southern Brazil

Based on small scale studies or on little sensitive serological tests, bovines in the south of the state of Rio Grande do Sul, Brazil, are known to be infected with either bovine herpesvirus 1 (BoHV-1) or 5 (BoHV-5). However, whether the prevalence of each of these viruses is high or low is currently still unknown. In order to determine the extent of BoHV (-1 and/or -5) infections in bovines in this region of Brazil, 200 bovines were studied for the presence of BoHV DNA. To this end, first a quantitative PCR was developed that amplified BoHV-1 DNA as well as BoHV-5 DNA. Using this PCR the number of BoHV genomes normally present in latently infected ganglia of naturally infected bovines was estimated. The new PCR was sensitive enough to detect most BoHV DNA in infected ganglia. The results of this first PCR showed that at least 87% of the bovines in the south of Rio Grande do Sul were (latently) infected with either BoHV-1 or BoHV-5. To determine the prevalence of BoHV-1 and BoHV-5 separately, two type-specific PCRs – one for each virus – were developed that used the products of the first PCR as a template. The results of these type-specific PCRs showed that 82.8% of the BoHV positive population was (latently) infected with BoHV-1, 93.1% with BoHV-5 and 75.9% with both BoHV-1 and BoHV-5. This is the first time that such a high frequency of co-infection of BoHV-1 and BoHV-5 in bovines has been demonstrated.