Comparative pathogenesis of acute and latent infections of calves with bovine herpesvirus types 1 and 5

Abstract

This study was conducted to compare the pathogenesis of acute and latent infections with closely related bovine herpesvirus types 1 (BHV-1) and 5 (BHV-5) in their natural host. Two groups of eight calves were inoculated intranasally with BHV-1 or BHV-5. Although BHV-1 and BHV-5 similarly replicate in the nasal mucosa after inoculation, both viruses differ markedly in their ability to cause disease, BHV-5 being responsible of some fatal encephalitis while BHV-1 inducing rhinotracheitis. Virus isolation and immunohistochemistry demonstrated that BHV-5 replicates extensively in neurons of the central nervous system (CNS) and in respiratory cells of lungs, tracheal and nasal mucosae. Invasion of the CNS likely occurs through the trigeminal and olfactory pathways. Both groups developed cross-neutralising antibodies during this experiment suggesting partial clinical cross-protection afforded by the two infections. Three months after primary infection, experimental reactivation showed that BHV-5 was able to establish latency in the trigeminal ganglia but also the CNS of surviving calves. Moreover, laboratory findings suggested that BHV-5 could also persist in the tracheal and nasal mucosae. These results indicate that, after primary infection, BHV-1 and BHV-5 displayed similar biological features and consequently need to be considered together for the control of BHV-1 infection.

Bovine herpesvirus 1 infection and infectious bovine rhinotracheitis

“…These sporadic cases probably reflect individual host susceptibilities to CNS infection rather than BoHV-1 strain modifications giving rise to an increased neuroinvasion and/or neurovirulence. Indeed, there was no evidence for specific BoHV-1 DNA restriction patterns associated to these strains isolated from cattle brains whereas the DNA restriction patterns showed clear differences between BoHV-1 and the neuropathogenic strains belonging to BoHV-5 [40,132]. But several host factors may account for increased susceptibility to CNS infection by BoHV-1 as suggested by recent data obtained on sporadic cases of encephalitis caused by HSV-1 in humans [26].…”

Ruminant alphaherpesviruses related to bovine herpesvirus 1

“…Comparative experiments of inoculation with BoHV-1 and BoHV-5 have been carried out in cattle [5,6,11,51,83,111]. After primary infection by intranasal inoculation, BoHV-1 and BoHV-5 replicate at the portal of entry in the respiratory mucosa [6].…”

“…Experimentally infected calves show similar profiles for the length of excretion (ten to sixteen days) and for the amount of excreted viruses. The rate of virus excretion is high, with a peak between the fourth and sixth days post infection [11,83,129]. After primary infection, BoHV-5 induces a transient viremia and virus is recovered in secondary organs [11].…”

“…In calves, BoHV-5 has been shown to produce fatal meningo-encephalitis after intranasal inoculation or a meningitis-like disease after intravaginal infection because the virus involves the central nervous system [5,83]. Inoculation of conjunctival, nasal and vaginal mucosae provokes conjunctivitis, rhinitis and vulvovaginitis, respectively.…”

“…Neurological signs start with severe depression with anorexia, jaw champing and hypersalivation. In the next phase, calves are affected by muscle trembling, circling to one side, pushing their head against a wall and ataxia, followed by seizure-like episodes and opisthotonos [83]. Histological lesions in the brain consist of meningitis, mononuclear perivascular cuffing, neurophagia, satellitosis, gliosis, haemorrhage, necrosis and oedema [92].…”