Abstract
The inaugural issue of Pathologia Veterinaria in 1964 contained the first detailed account of lesions in aborted fetuses following natural, experimental, and postvaccinal infection with bovine herpesvirus 1 (BoHV-1). The article, written by pathologists Kennedy and Richards, described diagnostic gross and histologic features in 13 bovine fetuses. The authors provided clinical and epidemiologic features of 1 postvaccination outbreak, including the absence of clinical signs in infected dams and the propensity for abortions to occur after 6 months' gestation. Subsequent field and experimental studies corroborated and expanded these observations. As a result of this and later reports, veterinarians became alert to the association between infectious bovine rhinotracheitis and abortion, including the risks of exposing pregnant cattle to live vaccinal BoHV-1. Methods were developed to corroborate a morphologic diagnosis of herpetic abortion in cattle, including immunofluorescence, immunohistochemistry, and polymerase chain reaction methods. Outbreaks of postvaccinal BoHV-1 abortion in the United States began to be reported with apparently increased frequency in the early 2000s. This coincided with licensure in 2003 of modified live BoHV-1 vaccines intended for use in pregnant cattle, which are now sold by 3 manufacturers. Ten recent herd episodes of postvaccinal BoHV-1 abortion are reported. All 10 BoHV-1 isolates had single-nucleotide polymorphism (SNPs) profiles previously identified in a group of BoHV-1 isolates that contains vaccine strains, based on a BoHV-1 SNP classification system. They lacked SNP features typical of those in characterized field-type strains of BoHV-1.
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