Julien Thiry

Biology of bovine herpesvirus 5.

Bovine herpesvirus 5 (BoHV-5) is an alphaherpesvirus responsible for meningoencephalitis in young cattle and is closely antigenically and genetically related to bovine herpesvirus 1 (BoHV-1). Both viruses have common aspects in their pathogenesis: (1) they infect epithelial cells at the portal of entry and (2) they establish a latent infection in the sensory nerve ganglia, i.e., the trigeminal ganglia. However, they have different neuroinvasion and neurovirulence capacities. Only in rare cases can BoHV-1 reach the brain of infected cattle. BoHV-5 infection induces different degrees of severity of neurological disease depending on both viral and host factors. Although a case of BoHV-5 associated disease in Europe and some outbreaks in USA and Australia have been reported, the current geographical distribution of BoHV-5 infection is mainly restricted to South America, especially Brazil and Argentina. This review focuses on the genomic characteristics, pathobiology and epidemiology of BoHV-5, in order to provide information on the possible basis of alphaherpesvirus neuropathogenesis.

Isolation and characterisation of a ruminant alphaherpesvirus closely related to bovine herpesvirus 1 in a free-ranging red deer

BackgroundThe genus Varicellovirus of the Herpesviridae subfamily Alphaherpesvirinae includes a cluster of viruses antigenically and genetically related to bovine herpesvirus 1 (BoHV-1): namely bovine herpesvirus 5 (BoHV-5), bubaline herpesvirus 1 (BuHV-1), caprine herpesvirus 1 (CpHV-1), cervid herpesviruses 1 (CvHV-1) and 2 (CvHV-2) and elk herpesvirus 1 (ElkHV-1). Considering the serological relationship between these ruminant alphaherpesviruses, several surveys have studied the occurrence of BoHV-1 related virus infection in wild and domestic ruminant species. In this way, a recent investigation has indicated, in Belgium, a high increase in the serological prevalence of BoHV-1 related virus infection in free-ranging red deer population. In this context, it has been decided to investigate the presence of an alphaherpesvirus spreading in the Belgian free-ranging red deer population.ResultsThe current study reports the first isolation in a free-ranging red deer of a BoHV-1 closely related virus. The isolate was antigenically, genomically and genetically characterised by comparison with several ruminant alphaherpesvirus. Immunofluorescence assays revealed the isolate was antigenically distinct from bovine and caprine alphaherpesviruses. Similarly, BamHI and BstEII restriction analyses demonstrated the genomic difference between the isolate and the other ruminant alphaherpesviruses. Next, the sequencing of selected parts of UL27 and US8 genes showed a high degree of homologies between each BoHV-1 related ruminant alphaherpesvirus and the isolate. Besides the close relationship between all ruminant alphaherpesviruses, the phylogenetic analysis revealed that the isolate clustered with CvHV-1.ConclusionThe first isolation of a virus closely related to BoHV-1 in a free-ranging red deer is reported. Data demonstrate that a CvHV-1 strain, named Anlier, circulates in wild red deer in continental Europe. Anlier strain show consistent differences with the virus isolated from Scottish farmed red deer. All together, these results improve our understanding of ruminant alphaherpesviruses.

Alphaherpesvirus infections in semidomesticated reindeer: a cross-sectional serological study.

Alphaherpesviruses infect a wide range of animal species and cause diseases. Cervid herpesvirus 2 (CvHV-2) was originally isolated from reindeer in Finland but the impact of CvHV-2 infections on reindeer remains unclear. CvHV-2 infection could be partly responsible for calf losses as there are indications that it is associated with abortions and neonatal diseases. Previous serosurveys of reindeer (Rangifer tarandus tarandus) have shown that an alphaherpesvirus is circulating among reindeer in Norway. The aim of the present study was to determine the prevalence of CvHV-2 infection among reindeer in various herding districts in Finnmark, the largest reindeer area in Norway, and to identify factors associated with becoming infected with CvHV-2. A total of 3062 serum samples were tested using an ELISA and a sub-set of samples was further tested using a seroneutralization test. The ELISA revealed that 49% of samples were positive. Extrapolation of the results to the total population (111,350 animals; 66% of the Finnmark reindeer population) showed that the seroprevalence in the population was 48%. Seroprevalence varied from 7.6% to 90.7% between districts and was affected by age, weight and population density. ELISA-positive samples neutralized CvHV-2 at serum dilutions greater than those required for neutralization of bovine herpesvirus type 1. It is concluded that CvHV-2 is endemic throughout the reindeer herding districts of northern Norway.

Cervid herpesvirus 2 experimentally reactivated in reindeer can produce generalized viremia and abortion.

Cervid herpesvirus 2 (CvHV2) has never been isolated from reindeer in Norway, but serological data and investigations by PCR indicate that the virus is endemic in the country, with horizontal and vertical transmission, systemic spread, and latency in the trigeminal ganglion. In this study two seropositive reindeer, one of which was pregnant, were administered dexamethasone, to reactivate CvHV2 latent infection. One control animal received sterile water. All animals including the control reactivated, as shown by amplification of CvHV2 DNA from nasal swabs. The pregnant animal showed lesions in the lip mucosa 10 days after the first dexamethasone injection and CvHV2 was visualized by electron microscopy and isolated from those lesions, as well as from nasal and vaginal swabs. On day 13 she aborted and CvHV2 was isolated from both the aborted calf and the mother. CvHV2 was isolated from the other animal administered dexamethasone. Despite amplification of viral DNA in the control animal, it was never possible to isolate the virus. Molecular characterization of the new isolates confirmed these to be CvHV2, and similar to the previous known strain Salla82. Present results represent the first isolation of CvHV2 in Norway and reconfirm that this virus can cause systemic infections in reindeer even after reactivation episodes, and infect the fetus in utero despite a prompt immune response. While it is not possible to atribute the abortion to CvHV2 alone, present data together with previous reports of vertical transmission of CvHV2 and neonatal death, point to an abortogenic potential, which should be further investigated.

Characterization of interspecific recombinants generated from closely related bovine herpesviruses 1 and 5 through multiple PCR sequencing assays

Bovine herpesviruses 1 (BoHV-1) and 5 (BoHV-5) are closely related alphaherpesviruses infecting cattle. In countries where both viruses circulate, co-infection of cattle is likely. It was shown that recombination occurs at a high frequency in cattle infected dually with two BoHV-1 mutants. In addition, interspecific recombinants are generated in cell culture co-infected with BoHV-1 and BoHV-5. Even if the process of interspecific recombination appears inefficient relative to intraspecific recombination, BoHV-1 and BoHV-5 may give rise to interspecific recombinants in co-infected cattle. Since molecular tools for differentiating BoHV-1 from BoHV-5 are limited and do not allow to localize recombination events between these closely related virus species, 13 PCR sequencing assays were developed to discriminate between BoHV-1 and BoHV-5 at regular intervals throughout the entire respective viral DNA genomes. These assays were used to determine the genetic background of two interspecific BoHV-1/-5 recombinants generated previously. The two crossover points where recombination events occurred between the parental strains were determined. This study provides a detailed analysis of two interspecific recombinant viruses generated in vitro from closely related alphaherpesviruses infecting the same natural host. It demonstrates that recombination can occur within very short fragments of sequence homology. This finding raises questions about the mechanisms involved in the strands exchange and resolution step of the homologous recombination used by herpesviruses. This method will allow monitoring generation of recombinants between closely related herpesvirus species both in vitro and in vivo.

Antimicrobial susceptibility monitoring of dermatological bacterial pathogens isolated from diseased dogs and cats across Europe (ComPath results)

The ComPath project is a pan‐European programme dedicated to the monitoring of antimicrobial susceptibility of pathogens from diseased dogs and cats using standardized methods and centralized minimum inhibitory concentration (MIC) determination. Here, the susceptibility of major pathogens is reported from antimicrobial nontreated animals with acute clinical signs of skin, wound or ear infections in 2008–2010.

Clinical protection against caprine herpesvirus 1 genital infection by intranasal administration of a live attenuated glycoprotein E negative bovine herpesvirus 1 vaccine

BackgroundCaprine herpesvirus 1 (CpHV-1) is responsible of systemic diseases in kids and genital diseases leading to abortions in goats. CpHV-1 is widespread and especially in Mediterranean countries as Greece, Italy and Spain. CpHV-1 is antigenically and genetically closely related to bovine herpesvirus 1 (BoHV-1). Taking into account the biological properties shared by these two viruses, we decided in the current study to assess the protection of a live attenuated glycoprotein E (gE) negative BoHV-1 vaccine against a genital CpHV-1 infection in goats.ResultsThe vaccine was inoculated intranasally twice three weeks apart followed by a subsequent CpHV-1 intravaginal challenge which is the natural route of infection in three goats. To analyse the safety and the efficacy of this marker vaccine, two groups of three goats served as controls: one immunised with a virulent CpHV-1 and one uninoculated until the challenge. Goats were clinically monitored and all sampling procedures were carried out in a blind manner. The vaccine did not induce any undesirable local or systemic reaction and goats did not excrete gE-negative BoHV-1. After challenge, a significant reduction in disease severity was observed in immunised goats. Moreover, goats immunised with either gE-negative BoHV-1 or CpHV-1 exhibited a significant reduction in the length and the peak of viral excretion. Antibodies neutralising both BoHV-1 and CpHV-1 were raised in immunised goats.ConclusionIntranasal application of a live attenuated gE-negative BoHV-1 vaccine is able to afford a clinical protection and a reduction of virus excretion in goats challenged by a CpHV-1 genital infection.

Isolation of cervid herpesvirus 1 from the genital tract of a farmed red deer in Northern France

In autumn 2008, several captive red deer in the North of France were found to be serologically positive for a ruminant alphaherpesvirus. A viral isolate obtained from the genital mucosa of a female red deer was characterised by sequencing and restriction endonuclease analyses as a cervid herpesvirus 1 closely related to Scottish Banffshire 82 strain.

In vitro-generated interspecific recombinants between bovine herpesviruses 1 and 5 show attenuated replication characteristics and establish latency in the natural host

BackgroundInterspecific recombinant viruses R1ΔgC and R2ΔgI were isolated after in vitro co-infection with BoHV-1 and BoHV-5, two closely related alphaherpesviruses that infect cattle. The genetic characterization of R1ΔgC and R2ΔgI showed that they are composed of different sections of the parental genomes. The aim of this study was the characterization of the in vivo behavior of these recombinants in the natural host.ResultsFour groups of four 3-month-old calves of both genders were intranasally inoculated with either the recombinant or parental viruses. A control group of two animals was also included. Viral excretion and clinical signs were monitored after infection. Histopathological examination of the central nervous system (CNS) was performed and the establishment of latency in trigeminal ganglia was analyzed by PCR. The humoral response was also evaluated using ELISA tests.Three out of four animals from the BoHV-5 infected group excreted virus for 4-10 days. Two calves shed R1ΔgC virus for one day. In R2ΔgI and BoHV-1.2ΔgCΔgI groups, infectious virus was isolated only after two or three blind passages. None of the infected animals developed neurological signs, although those infected with BoHV-5 showed histopathological evidence of viral infection. Latent viral DNA was detected in at least one calf from each infected group. Serum and/or mucosal antibodies were detected in all groups.ConclusionBoth BoHV-1/-5 recombinants and the BoHV-1 parental strain are attenuated in calves, although they are able to replicate in animals at low rates and to establish latent infections.

Experimental Infection of Reindeer with Cervid Herpesvirus 2

ABSTRACT Cervid herpesvirus 2 (CvHV2) has been isolated from reindeer (Rangifer tarandus tarandus), and serological data indicate that in reindeer this virus is endemic in Fennoscandia, Alaska, Canada, and Greenland. CvHV2 has been described as a cause of subclinical genital infections in reindeer, but little information on primary infections exists. In this study, six seronegative and presumably pregnant reindeer were allocated to one of two groups. Two animals were inoculated with CvHV2 intratracheally, and two animals intravaginally, with one control animal in each group receiving sterile water. Mild hyperthermia and serous discharges from the vagina and nose were observed. No abortions were recorded, but one calf died shortly after birth. Inoculated animals seroconverted and had neutralizing antibodies after days 7 to 10 postinfection. CvHV2 was detected by PCR in nasal and vaginal swabs from animals in both groups but could be isolated only from nasal swabs in the respiratory group and from vaginal swabs in the genital group. CvHV2 was detected by PCR in various organs and tissues postmortem. In control animals, the virus could not be isolated in spite of PCR-positive nasal and vaginal swab samples and some degree of positive immunostaining. One of the animals that were inoculated intratracheally developed a hemorrhagic, necrotizing bronchopneumonia, which was CvHV2 positive by PCR and immunohistochemistry. We conclude that CvHV2 can cause systemic infection, that both genital and respiratory inoculations can lead to virus shedding, and that the virus can infect the fetus in utero.