Mylène Lemaire

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

Summary. 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.

Latency and reactivation of a glycoprotein E negative bovine herpesvirus type 1 vaccine: influence of virus load and effect of specific maternal antibodies.

The effects of the vaccination of neonatal calves with a glycoprotein E (gE)-negative bovine herpesvirus type 1 (BHV-1) were investigated in naïve and passively immunised calves either with the recommended dose or a 5-fold concentrated one. After inoculation (PI), all calves excreted the virus vaccine except three passively immunised calves inoculated with the lower titre. No antibody response could be detected in passively immunised calves, whatever the dose used, and they all became BHV-1 seronegative and remained so after dexamethasone treatment (PDT). Nevertheless, as shown by a gamma-interferon assay, all calves that excreted the vaccine PI developed a cell-mediated immune response and a booster response was observed PDT, suggesting viral reactivation. The vaccine virus was recovered PDT from nasal secretions in two calves and BHV-1 DNA were detected in trigeminal ganglia from five calves belonging to all inoculated groups. The results show that the BHV-1 gE-negative vaccine can establish latency not only in naïve but also in passively immunised neonatal calves after a single intranasal inoculation. Moreover, this study shows for the first time that the gE-negative vaccine, when used in passively immunised calves, can lead to seronegative vaccine virus carriers.

Establishment of a rabbit model for bovine herpesvirus type 5 neurological acute infection.

This study was conducted to evaluate the suitability of the rabbit as a model for bovine, herpesvirus 5 (BHV-5) acute infection. In a preliminary experiment, a total of 24 one-month old New Zealand white rabbits were inoculated with BHV-5 or bovine herpesvirus 1 (BHV-1) by the intraconjunctival, intracerebral or intranasal routes. BHV-5 or BHV-1 inoculated in the conjunctiva induced virus proliferation in the eye mucosae and the nasal cavity of rabbits without meningo-encephalitis. On the other hand, only BHV-5 infection by intranasal or intracerebral routes produced a fatal meningo-encephalitis. The intranasal route was used in a further experiment for the establishment of a rabbit model for BHV-5 infection. A total of 45 rabbits were inoculated intranasally with BHV-5 or BHV-1. The results showed that intranasal inoculation of BHV-5 strain N569 in rabbits was followed by the development of a lethal meningo-encephalitis for 66% of rabbits while all BHV-1 infected rabbits remained healthy throughout this experiment (28 days). Analysis between the mortalities of rabbits infected with BHV-5 and BHV-1 were highly significant (p < 0.001). The presence of BHV-5 in the central nervous system (CNS) was confirmed by virus isolation (essentially the cerebrum, midbrain and pons) and by immunohistochemical staining of BHV-5 antigen (essentially in the neurons of the cerebrum) only in BHV-5 infected rabbits showing clinical signs of meningo-encephalitis. The findings obtained confirmed the suitability of a rabbit model for the establishment of BHV-5 neurological acute infection and also as a valuable tool for the comparative study of BHV-5 and BHV-1 neuropathogenicity.

Lethal bluetongue virus serotype 1 infection in llamas.

Screening for Chagas disease should be recommended to all Latin American migrants, especially those from Bolivia. This screening would enable early treatment for persons in the chronic asymptomatic phase or those with mild cardiac involvement, persons for whom treatment has been recommended (9). Current legislation in Spain makes screening all at-risk blood donors mandatory (10). However, screening of pregnant women from Chagas disease–endemic countries is not compulsory, although 46.8% of immigrants in Spain are female and birth rates in this group are higher than the national average for Spain (5). Detection of antibodies to T. cruzi during pregnancy would also be a useful public health strategy because it would enable early specifi c treatment of affected newborns. Screening of blood or organ donors would also be necessary in countries where there is no transmission by vectors. T. cruzi infection may become a public health problem in countries in Europe that receive immigrants from disease-endemic areas. Thus, chagasic cardiomyopathy may soon have a serious effect on public health in Spain.

A specific PCR to differentiate between gE negative vaccine and wildtype bovine herpesvirus type 1 strains

In the context of infectious bovine rhinotracheitis (IBR) control programmes using glycoprotein E (gE) deleted marker vaccines, a PCR assay was developed to allow the genotypic differentiation between wildtype bovine herpesvirus type 1 (BoHV-1) and gE negative strains. This assay is based on the PCR amplification of a 281 bp DNA fragment within the gE gene. The specificity of the amplification was confirmed by restriction endonuclease analysis and nucleotide sequencing of the PCR product. Its ability to determine the gE genotype of BoHV-1 strains was demonstrated on isolates coming from 20 experimental calves infected with four different BoHV-1 strains. This PCR assay may be a useful tool for monitoring the spread of live marker vaccine and the gE genotype of viral field isolates.

ANTIBODY RESPONSE TO GLYCOPROTEIN E AFTER BOVINE HERPESVIRUS TYPE 1 INFECTION IN PASSIVELY IMMUNISED, GLYCOPROTEIN E-NEGATIVE CALVES

This study was conducted to determine whether young calves with maternal antibodies against bovine herpesvirus type 1 (BHV-1) but without antibodies against glycoprotein E (gE) can produce an active antibody response to gE after a BHV-1 infection. Five calves received at birth colostrum from gE-seronegative cows which had been vaccinated two or three times with an inactivated BHV-1, gE-deleted marker vaccine. After inoculation with a wild-type virulent strain of BHV-1, all the passively immunised gE-negative calves shed virus in large amounts in their nasal secretions. All the calves seroconverted to gE within two to four weeks after inoculation and then had high levels of gE antibodies for at least four months. The development of an active cell-mediated immune response was also detected by in vitro BHV-1-specific interferon-gamma assays. All the calves were latently infected, because one of them re-excreted the virus spontaneously and the other four did so after being treated with dexamethasone. The results showed that under the conditions of this work the gE-negative marker could also distinguish between passively immunised and latently infected calves.

Isolation of a glycoprotein E-deleted bovine herpesvirus type 1 strain in the field

During a field trial to evaluate the efficacy of repeated vaccinations with bovine herpesvirus type 1 (BHV-1) marker vaccines, a glycoprotein E (gE)-negative BHV-1 strain was isolated from the nasal secretions of two cows, eight months after vaccination with a gE-negative live-attenuated vaccine, initially given intranasally, then intramuscularly. The strain isolated was characterised using immunofluorescence, restriction analysis and CR. All the techniques used identified the isolated virus as a gE-negative BHV-1 phenotypically and genotypically identical to the Za strain used as a control.

Cross-sectional study of the association between pathological conditions and myxoma-virus seroprevalence in intensive rabbit farms in Europe

Myxomatosis is a major viral disease of the European rabbit (Oryctolagus cuniculus). Two forms of the disease (nodular and amyxomatous) exist. The clinical diagnosis of the nodular form is easily performed on the basis of typical skin lesions whereas that of amyxomatous forms must be based on virus isolation or detection of specific antibodies to myxoma virus (MV). The seroprevalence of MV was studied between March 1998 and February 1999 in 16 farms from three European countries considered free of myxomatosis on the basis of the absence of typical clinical signs. MV antibodies were detected by enzyme-linked immunosorbent assay (ELISA) (sensitivity 100%, specificity 90%) in all 16 farms; the seroprevalences corrected for test inaccuracy (95% confidence interval) were 55+/-7.7% and 37+/-6.1% for does and broilers, respectively. The association between herd sizes, types of rabbitries, and presence of recurrent respiratory or digestive troubles and seroprevalence of MV antibodies was tested in logistic multiple regressions. In all models, the seroprevalence of MV antibodies was significantly higher in herds (does and broilers) with recurrent respiratory or digestive troubles than in herds without these problems. The seroprevalence was also higher in herds (does and broilers) where animals were housed totally or partially in outdoors rabbitries than in totally enclosed rabbitries. The effect of herd sizes on the presence of MV antibodies was the same in does and broilers; intermediate sizes were at lower risk than the smaller and larger ones.

Bluetongue Virus Serotype 1 in Wild Ruminants, France, 2008–10

The persistence of Bluetongue virus serotype 1 (BTV-1) circulation was evaluated in red deer (Cervus elaphus), roe deer (Capreolus capreolus), mouflons (Ovis ammon), and Pyrenean chamois (Rupicapra pyrenaica pyrenaica) sampled during two hunting seasons between September 2008 and February 2010 in the East Pyrenean Mountains, France. The prevalence of BTV antibody in red deer was high and not significantly different between the two hunting seasons (50.9% and 49.6%, respectively). The prevalence of BTV-1 RNA in red deer was 50.3% in 2008. Conversely, only 10.8% of samples from red deer were BTV-1 RNA–positive in 2010, and most of them showed only weak positive results. In other investigated species, the prevalence of infection was low. High elevation was associated with reduced infection rates and could explain the low prevalence observed in mouflons and Pyrenean chamois. These results support the hypothesis that, apart from red deer, wild ungulates are unlikely to be involved in the maintenance or circulation of BTV in the investigated region. Mass vaccination in livestock might have reduced BTV-1 circulation in red deer, although annual variation due to acquired immunity or fluctuations in vector abundance should also be considered.

Prevalence of antibodies to human adenovirus type 5 in Belgian cattle

A. J. (1993) Kinematic gait analysis in equine carpal lameness. Acta Anatomica 146, 86-89 BUCHNER, H. H. F., KASTNER, J., GIRTLER, D. & KNEZEVIC, P. F. (1993) Quantification ofhindlimb lameness in the horse. Acta Anatomica 146,196-199 BUCHNER, H. H. F., SAVELBERG, H. H. C. M., SCHAMHARDT, H. C. & BARNEVELD, A. (1996) Head and trunk movement adaptions in horses with experimentally induced foreor hindlimb lameness. Equine Veterinary Journal 28, 71-76 BUCHNER, H. H. F., SAVELBERG, H. H. C. M., SCHAMHARDT, H. C., MERKENS, H. W. & BARNEVELD, A. (1994) Habituation of horses to treadmill locomotion. Equine Veterinary Journal Supplement 17, 13-15 KEEGAN, K. G., WILSON, D. A., WILSON, D. J., SMITH B., GAUGHAN, E. M., PLEASANT, R. S., LILLICH, J. D., KRAMER, J., HOWARD, R. D., BACON-MILLER, C., DAVIES, E. G., MAY, K. A., CHERAMIE, H. S., VALENTINO, W. L. & VAN HARREVELD, P. D. (1998) Evaluation of mild lameness in horses trotting on a treadmill by clinicians and interns or residents and correlation of their assessments with kinematic gait analysis. American Journal of Veterinary Research 59, 1370-1377 KEG, P. R.,VAN WEEREN, P. R., BACK, W. & BARNEVELD, A. (1997) Influence of the force applied and its period of application on the outcome of the flexion test of the distal fore limb of the horse. Veterinary Record 141,463-466 PEHAM, C., LICKA, T., MAYR, A., SCHEIDL, M. & GIRTLER, D. (1998) Speed dependency of motion pattern consistency. Journal ofBiomechanics 31,769-772 PEHAM, C., LICKA, T., SCHEIDL, M. & GIRTLER, D. (1999) Supporting forelimb lameness: clinical judgement versus computerized symmetry measurement. Equine Veterinary Journal 31, 417-421 PEHAM, C., SCHEIDL, M. & LICKA, T. (1996) A method of signal processing in motion analysis of the trotting horse. Journal ofBiomechanics 29, 1111-1114 UHLIR, C., LICKA, T., KUBBER, P., PEHAM, C., SCHEIDL, M. & GIRTLER, D. (1997) Compensatory movements of horses with a stance phase lameness. Equine Veterinary Journal Supplement 23, 102-105