PESQUISA VETERINÁRIA BRASILEIRA

Abstract in English:

ABSTRACT.- Rissi D.R., Rech R.R., Flores E.F., Kommers G.D. & Barros C.S.L. 2007. [Meningoencephalitis by bovine herpesvirus-5.] Meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira 27(7):251-260. Departamento de Patologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. E-mail: claudioslbarros@uol.com.br Meningoencephalitis caused by bovine herpesvirus-5 (BoHV-5) is an often fatal, acute or subacute infectious disease that affects mainly young cattle under stressing conditions. The disease has been recognized in several Brazilian regions and in other parts of the world. BoHV-5 is a double stranded DNA virus member of the Herpesviridae family and subfamily Alphaherpesvirinae. The virus is characterized by rapid and lytic replication in cell cultures and by the ability to establish lifelong latent infection in sensory nerve ganglia of the host. BoHV-5 is transmitted mainly by direct and indirect contact and replicates acutely in the oral, nasal, oropharingeal or ocular mucosae. After primary replication, the virus invades nerve endings and is transported to the neuron cell bodies of the sensory ganglia where it replicates actively and/or establishes latency. Viral invasion of the brain may result in massive virus replication and production of neurological disease. Virtually all cattle developing neurological disease die of meningoencephalitis; yet the infection may be subclinical in some animals. These animals recover and become latently infected. Viral dissemination within a herd is facilitated by conditions such as crowding, introduction of cattle from other herds and weaning of calves in ages that coincide with decrease of passive immunity. Certain natural or induced conditions may reactivate the latent virus and favor its transmission and dissemination to other susceptible individuals. The disease may occur as outbreaks or as sporadic cases, with morbidity rates ranging of 0.05%-5%; lethality is almost always 100%. Clinical signs include depression, nasal and ocular discharge, grinding of teeth, circling, blindness, fever, paddling movements, disphagia, abdominal pain, nystagmus, muscle tremors, drooling, incoordinated gait, opisthotonus, head pressing, falls and convulsions. Clinical course is usually 1-15 days. Necropsy findings may be absent but often there is swollen of the rostral portions of the cerebral cortex and flattening of gyri, with softening and segmental yellow discoloration (malacia). As the disease progresses the affected areas become gelatinous and grey and, in advanced cases, there is segmental loss of the cerebral cortex of the frontal lobe of the brain (residual lesion). In several cases there is malacia of the basal nuclei and of the thalamus. Histologically, there is necrotizing non-suppurative meningoencephalitis affecting mainly the cerebral cortex of the frontal lobe associated with eosinophilic intranuclear inclusion bodies in neurons and astrocytes, although the frequency of the inclusion bodies is inconsistent. The diagnosis of meningoencephalitis by BoHV-5 should be based on epidemiology, clinical signs, necropsy and histological findings. The diagnosis should be confirmed by viral isolation in cell culture and/or by detection of viral antigens in brain sections or in exfoliated cells from nasal secretions. The identification and characterization of BoHV-5 can be done by the use of monoclonal antibodies, polymerase chain reaction (PCR) and/or by restriction enzyme analysis of the viral genome. There is no specific treatment for the disease. As BoHV-1 and BoHV-5 are antigenically related, vaccination using BoHV-1 vaccines may be recommended as a means of reducing the losses caused by BoHV-5 infection, mainly during outbreaks of neurologic disease. Additionally, measures such as serologic testing of new additions to the herd; and management practices to prevent stress and to reduce conditions for virus dissemination among animals may help in reducing the incidence and the consequences of BoHV-5 infection and disease.

• Bovine herpesvirus-5 BoHV-5 BHV-5 meningoencephalitis viral diseases diseases of cattle neuropathology

Abstract in Portuguese:

ABSTRACT.- Rissi D.R., Rech R.R., Flores E.F., Kommers G.D. & Barros C.S.L. 2007. [Meningoencephalitis by bovine herpesvirus-5.] Meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira 27(7):251-260. Departamento de Patologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. E-mail: claudioslbarros@uol.com.br Meningoencephalitis caused by bovine herpesvirus-5 (BoHV-5) is an often fatal, acute or subacute infectious disease that affects mainly young cattle under stressing conditions. The disease has been recognized in several Brazilian regions and in other parts of the world. BoHV-5 is a double stranded DNA virus member of the Herpesviridae family and subfamily Alphaherpesvirinae. The virus is characterized by rapid and lytic replication in cell cultures and by the ability to establish lifelong latent infection in sensory nerve ganglia of the host. BoHV-5 is transmitted mainly by direct and indirect contact and replicates acutely in the oral, nasal, oropharingeal or ocular mucosae. After primary replication, the virus invades nerve endings and is transported to the neuron cell bodies of the sensory ganglia where it replicates actively and/or establishes latency. Viral invasion of the brain may result in massive virus replication and production of neurological disease. Virtually all cattle developing neurological disease die of meningoencephalitis; yet the infection may be subclinical in some animals. These animals recover and become latently infected. Viral dissemination within a herd is facilitated by conditions such as crowding, introduction of cattle from other herds and weaning of calves in ages that coincide with decrease of passive immunity. Certain natural or induced conditions may reactivate the latent virus and favor its transmission and dissemination to other susceptible individuals. The disease may occur as outbreaks or as sporadic cases, with morbidity rates ranging of 0.05%-5%; lethality is almost always 100%. Clinical signs include depression, nasal and ocular discharge, grinding of teeth, circling, blindness, fever, paddling movements, disphagia, abdominal pain, nystagmus, muscle tremors, drooling, incoordinated gait, opisthotonus, head pressing, falls and convulsions. Clinical course is usually 1-15 days. Necropsy findings may be absent but often there is swollen of the rostral portions of the cerebral cortex and flattening of gyri, with softening and segmental yellow discoloration (malacia). As the disease progresses the affected areas become gelatinous and grey and, in advanced cases, there is segmental loss of the cerebral cortex of the frontal lobe of the brain (residual lesion). In several cases there is malacia of the basal nuclei and of the thalamus. Histologically, there is necrotizing non-suppurative meningoencephalitis affecting mainly the cerebral cortex of the frontal lobe associated with eosinophilic intranuclear inclusion bodies in neurons and astrocytes, although the frequency of the inclusion bodies is inconsistent. The diagnosis of meningoencephalitis by BoHV-5 should be based on epidemiology, clinical signs, necropsy and histological findings. The diagnosis should be confirmed by viral isolation in cell culture and/or by detection of viral antigens in brain sections or in exfoliated cells from nasal secretions. The identification and characterization of BoHV-5 can be done by the use of monoclonal antibodies, polymerase chain reaction (PCR) and/or by restriction enzyme analysis of the viral genome. There is no specific treatment for the disease. As BoHV-1 and BoHV-5 are antigenically related, vaccination using BoHV-1 vaccines may be recommended as a means of reducing the losses caused by BoHV-5 infection, mainly during outbreaks of neurologic disease. Additionally, measures such as serologic testing of new additions to the herd; and management practices to prevent stress and to reduce conditions for virus dissemination among animals may help in reducing the incidence and the consequences of BoHV-5 infection and disease.

Abstract in English:

ABSTRACT.- Rissi D.R., Oliveira F.N., Rech R.R., Pierezan F., Lemos R.A.A. & Barros C.S.L. 2006. [Epidemiology, clinical signs and distribution of the encephalic lesions in cattle affected by meningoencephalitis caused by bovine herpesvirus-5.] Epidemiologia, sinais clínicos e distribuição das lesões encefálicas em bovinos afetados por meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira 26(2):123-132. Departamento de Patologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. E-mail: claudioslbarros@uol.com.br Seven outbreaks and an isolated case of meningoencephalitis caused by bovine herpesvirus-5 (BoHV-5) in cattle in Rio Grande do Sul, Brazil, occurring in 2002-2004, are described. From a total population at risk of 1,359 cattle, 54 1-18-month-old calves from both sexes and several breeds were affected and 50 died spontaneously or were euthanatized while moribund. The highest frequency of cases was in recently weaned calves or calves submitted to other stressing factors. General rates of morbidity, mortality and lethality were respectively 3.97, 3.67 and 92.59%. Clinical courses varied from 3-10 days and included depression, nasal and ocular discharge, grinding of teeth, circling, blindness, fever, nistagmus, trembling, anorexia, dysphagia, drooling, incoordination, head pressing, rough hair coat, tachycardia, tachypnea, abdominal pain, melena, falls, recumbency, opisthotonus, convulsions and paddling. Nineteen calves were necropsied. Necropsy findings were characterized by hyperemia of leptomeninges, swollen rostral portions of the telencephalon, and flattening of frontal lobes gyri; frequently in these frontal areas there were segmental brown-yellow discoloration and softening (malacia) of the cortex. In cases with more protracted clinical courses there were extensive swelling, softening and hemorrhaging of the telencephalic frontal lobes. Microscopically, all affected cattle had a necrotizing non-suppurative meningoencephalitis with variable distribution among the 19 cases and among the various telencephalic regions of the same case. The severity of these changes were more marked, in decreasing order of intensity, in the telencephalic frontal cortex, basal ganglia (nuclei), thalamus, brain stem, parietal telencephalic cortex, occipital telencephalic cortex and cerebellum. Perivascular inflammatory infiltrate consisted predominantly of lymphocytes, plasm cells, and less frequently of neutrophils. Additional microscopic findings included variable degrees of gliosis, edema, neuronal necrosis in the telencephalic cortex characterized by shrinking and eosinophilia of perikaria and nuclear picnosis (red neuron); basophilic intranuclear inclusion bodies in astrocytes and neurons (21.05% of the cases); sattelitosis; and neuronophagia. The areas of softening in the cortical substance consisted of necrosis of the neuroctodermal elements with maintenance of mesenchymal structures (vessels and microglia), infiltrate of Gitter cells, and, in more severe cases, extensive hemorrhages. In chronic cases, only vascular structures and a few Gitter cells remained in the cortical area leaving a cavity between white matter and leptomeninges (residual lesion).

• Bovine herpesvirus-5 BoHV-5 encephalitis diseases of cattle viral diseases neuropathology.

Abstract in Portuguese:

ABSTRACT.- Rissi D.R., Oliveira F.N., Rech R.R., Pierezan F., Lemos R.A.A. & Barros C.S.L. 2006. [Epidemiology, clinical signs and distribution of the encephalic lesions in cattle affected by meningoencephalitis caused by bovine herpesvirus-5.] Epidemiologia, sinais clínicos e distribuição das lesões encefálicas em bovinos afetados por meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira 26(2):123-132. Departamento de Patologia, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. E-mail: claudioslbarros@uol.com.br Seven outbreaks and an isolated case of meningoencephalitis caused by bovine herpesvirus-5 (BoHV-5) in cattle in Rio Grande do Sul, Brazil, occurring in 2002-2004, are described. From a total population at risk of 1,359 cattle, 54 1-18-month-old calves from both sexes and several breeds were affected and 50 died spontaneously or were euthanatized while moribund. The highest frequency of cases was in recently weaned calves or calves submitted to other stressing factors. General rates of morbidity, mortality and lethality were respectively 3.97, 3.67 and 92.59%. Clinical courses varied from 3-10 days and included depression, nasal and ocular discharge, grinding of teeth, circling, blindness, fever, nistagmus, trembling, anorexia, dysphagia, drooling, incoordination, head pressing, rough hair coat, tachycardia, tachypnea, abdominal pain, melena, falls, recumbency, opisthotonus, convulsions and paddling. Nineteen calves were necropsied. Necropsy findings were characterized by hyperemia of leptomeninges, swollen rostral portions of the telencephalon, and flattening of frontal lobes gyri; frequently in these frontal areas there were segmental brown-yellow discoloration and softening (malacia) of the cortex. In cases with more protracted clinical courses there were extensive swelling, softening and hemorrhaging of the telencephalic frontal lobes. Microscopically, all affected cattle had a necrotizing non-suppurative meningoencephalitis with variable distribution among the 19 cases and among the various telencephalic regions of the same case. The severity of these changes were more marked, in decreasing order of intensity, in the telencephalic frontal cortex, basal ganglia (nuclei), thalamus, brain stem, parietal telencephalic cortex, occipital telencephalic cortex and cerebellum. Perivascular inflammatory infiltrate consisted predominantly of lymphocytes, plasm cells, and less frequently of neutrophils. Additional microscopic findings included variable degrees of gliosis, edema, neuronal necrosis in the telencephalic cortex characterized by shrinking and eosinophilia of perikaria and nuclear picnosis (red neuron); basophilic intranuclear inclusion bodies in astrocytes and neurons (21.05% of the cases); sattelitosis; and neuronophagia. The areas of softening in the cortical substance consisted of necrosis of the neuroctodermal elements with maintenance of mesenchymal structures (vessels and microglia), infiltrate of Gitter cells, and, in more severe cases, extensive hemorrhages. In chronic cases, only vascular structures and a few Gitter cells remained in the cortical area leaving a cavity between white matter and leptomeninges (residual lesion).

Abstract in English:

Riet-Correa G., Duarte M.D., Barbosa J.D., Oliveira C.M.C., Cerqueira V.D., Brito M.F. & Riet-Correa F. 2006. [Meningoencephalitis and polioencephalomalacia caused by Bovine herpesvirus-5 in the state of Pará, northern Brazil.] Meningoencefalite e polioencefalomalacia causadas por Herpesvírus bovino-5 no Estado do Pará. Pesquisa Veterinária Brasileira 26(1):44-46. Central de Diagnóstico Veterinário, Universidade Federal do Pará, Maximino Porpino 1000, Castanhal, PA 68740-080, Brazil. E-mail: griet@ufpa.br Four outbreaks of meningoencephalitis in 1 to 2 years old cattle caused by Bovine herpesvirus-5 are reported in four municipalities in the state of Pará, northern Brazil. In three outbreaks only one animal was affected, in another 3 cattle were affected. Main clinical signs were incoordination, dullness, blindness, recumbence, and opisthotonus. Death occurred after a clinical manifestation period of 3-4 days. Softening and yellowish areas were observed grossly in the cerebral cortex. The histology revealed poliencephalomalacia in the cerebral cortex, thalamus and basal nuclei, and non suppurative encephalitis and meningitis, and eosinophilic intranuclear inclusion bodies in astrocytes. The diagnosis was based on the typical microscopic lesions.

• Meningoencephalitis polioencephalomalacia bovine herpesvirus-5 cattle.

Abstract in Portuguese:

Riet-Correa G., Duarte M.D., Barbosa J.D., Oliveira C.M.C., Cerqueira V.D., Brito M.F. & Riet-Correa F. 2006. [Meningoencephalitis and polioencephalomalacia caused by Bovine herpesvirus-5 in the state of Pará, northern Brazil.] Meningoencefalite e polioencefalomalacia causadas por Herpesvírus bovino-5 no Estado do Pará. Pesquisa Veterinária Brasileira 26(1):44-46. Central de Diagnóstico Veterinário, Universidade Federal do Pará, Maximino Porpino 1000, Castanhal, PA 68740-080, Brazil. E-mail: griet@ufpa.br Four outbreaks of meningoencephalitis in 1 to 2 years old cattle caused by Bovine herpesvirus-5 are reported in four municipalities in the state of Pará, northern Brazil. In three outbreaks only one animal was affected, in another 3 cattle were affected. Main clinical signs were incoordination, dullness, blindness, recumbence, and opisthotonus. Death occurred after a clinical manifestation period of 3-4 days. Softening and yellowish areas were observed grossly in the cerebral cortex. The histology revealed poliencephalomalacia in the cerebral cortex, thalamus and basal nuclei, and non suppurative encephalitis and meningitis, and eosinophilic intranuclear inclusion bodies in astrocytes. The diagnosis was based on the typical microscopic lesions.

Abstract in English:

Diel D.G., Fonseca E.T., Souza S.F., Mazzanti A., Bauermann F., Weiblen R. & Flores E.F. 2005. [Bovine herpesvirus 5 may use the olfactory and trigeminal pathways to invade the central nervous system of rabbits, depending upon the route of inoculation.] O Herpesvírus bovino tipo 5 (BoHV-5) pode utilizar as rotas olfatória ou trigeminal para invadir o sistema nervoso central de coelhos, dependendo da via de inoculação. Pesquisa Veterinária Brasileira 25(3):164-170. Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil. E-mail: flores@ccr.ufsm.br Bovine herpesvirus type 5 (BoHV-5) is a major etiological agent of meningoencephalitis in cattle. Following replication in the nasal mucosa, viral invasion of the brain is thought to occur mainly by the olfactory pathway. To address the role of this pathway in the pathogenesis of neurological infection in a laboratory model, 30 days old rabbits had the main olfactory bulbs (MOBs) surgically removed and were subsequently inoculated intranasally (IN) or conjunctivally (IC) with a highly neurovirulent BoHV-5 strain (SV-507). Following IN inoculation, 10 out of 10 (100 %) control rabbits developed neurological disease. The clinical onset ranged from day 5 to 10 post-inoculation (pi, average 7.5 days); nine being euthanized in extremis and one recovering after a mild clinical course. In contrast, only one rabbit (9.1 %) of the group lacking the MOBs (n=11) developed neurological disease (onset at day 17 pi). Dexamethasone administration to the survivors (n=10) at day 50pi was followed by virus shedding in nasal and/or ocular secretions by 8 animals, demonstrating that the virus was able to reach the trigeminal ganglia (TG) during acute infection. These results demonstrate that the olfactory route provides the main, yet not the sole access to the brain of rabbits following IN inoculation. To address the role of a second pathway, groups of control (n=12) or MOB-lacking rabbits (n=12) were inoculated into the conjunctival sac (IC), following which the virus would be expected to use the ophtalmic branch of the trigeminal nerve to reach the brain. Ten control rabbits (83.3 %) developed neurological disease upon IC inoculation (onset 15.3 days [11 to 20]). Previous ablation of the MOBs did not affect the frequency and course of neurological disease: ten out of 12 rabbits (83.3 %) lacking the MOBs developed neurological disease (onset 9 to 15 dpi, average: 12.7 days) upon IC inoculation. These results demonstrate that both IN and IC routes may operate in the transport of BoHV-5 to the brain of experimentally infected rabbits, depending on the route of inoculation. IN inoculation results in a fast and efficient transport by the olfactory pathway, the trigeminal route providing an alternative, much slower and less efficient transport; IC inoculation results in efficient viral transport by the trigeminal route, yet with a delayed kinetics comparing to the transport provided by the olfactory pathway.

• Bovine herpesvirus type 5 BoHV-5 neurological infection rabbits.

Abstract in Portuguese:

Diel D.G., Fonseca E.T., Souza S.F., Mazzanti A., Bauermann F., Weiblen R. & Flores E.F. 2005. [Bovine herpesvirus 5 may use the olfactory and trigeminal pathways to invade the central nervous system of rabbits, depending upon the route of inoculation.] O Herpesvírus bovino tipo 5 (BoHV-5) pode utilizar as rotas olfatória ou trigeminal para invadir o sistema nervoso central de coelhos, dependendo da via de inoculação. Pesquisa Veterinária Brasileira 25(3):164-170. Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil. E-mail: flores@ccr.ufsm.br Bovine herpesvirus type 5 (BoHV-5) is a major etiological agent of meningoencephalitis in cattle. Following replication in the nasal mucosa, viral invasion of the brain is thought to occur mainly by the olfactory pathway. To address the role of this pathway in the pathogenesis of neurological infection in a laboratory model, 30 days old rabbits had the main olfactory bulbs (MOBs) surgically removed and were subsequently inoculated intranasally (IN) or conjunctivally (IC) with a highly neurovirulent BoHV-5 strain (SV-507). Following IN inoculation, 10 out of 10 (100 %) control rabbits developed neurological disease. The clinical onset ranged from day 5 to 10 post-inoculation (pi, average 7.5 days); nine being euthanized in extremis and one recovering after a mild clinical course. In contrast, only one rabbit (9.1 %) of the group lacking the MOBs (n=11) developed neurological disease (onset at day 17 pi). Dexamethasone administration to the survivors (n=10) at day 50pi was followed by virus shedding in nasal and/or ocular secretions by 8 animals, demonstrating that the virus was able to reach the trigeminal ganglia (TG) during acute infection. These results demonstrate that the olfactory route provides the main, yet not the sole access to the brain of rabbits following IN inoculation. To address the role of a second pathway, groups of control (n=12) or MOB-lacking rabbits (n=12) were inoculated into the conjunctival sac (IC), following which the virus would be expected to use the ophtalmic branch of the trigeminal nerve to reach the brain. Ten control rabbits (83.3 %) developed neurological disease upon IC inoculation (onset 15.3 days [11 to 20]). Previous ablation of the MOBs did not affect the frequency and course of neurological disease: ten out of 12 rabbits (83.3 %) lacking the MOBs developed neurological disease (onset 9 to 15 dpi, average: 12.7 days) upon IC inoculation. These results demonstrate that both IN and IC routes may operate in the transport of BoHV-5 to the brain of experimentally infected rabbits, depending on the route of inoculation. IN inoculation results in a fast and efficient transport by the olfactory pathway, the trigeminal route providing an alternative, much slower and less efficient transport; IC inoculation results in efficient viral transport by the trigeminal route, yet with a delayed kinetics comparing to the transport provided by the olfactory pathway.

Abstract in English:

Spilki F.R., Silva A.D., Batista H.B.C.R., Oliveira A.P., Winkelmann E., Franco A.C., Porciúncula J.A. & Roehe P.M. 2005. Field evaluation of safety during gestation and horizontal spread of a recombinant differential bovine herpesvirus 1 (BoHV-1) vaccine. Pesquisa Veterinária Brasileira 25(1):54-58. Instituto de Pesquisa Veterinária Desidério Finamor, Fepagro-Saúde Animal, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@ufrgs.br Bovine herpesvirus type 1 (BoHV-1) is recognized as a major cause of respiratory, reproductive disease and abortion in cattle. Vaccination is widely applied to minimize losses induced by BoHV-1 infections; however, vaccination of dams during pregnancy with modified live virus (MLV) vaccines has been occasionally associated to abortions. We have previously reported the development of a BoHV-1 recombinant virus, constructed with basis on a Brazilian BoHV-1 (Franco et al. 2002a) from which the gene coding for glycoprotein E (gE) was deleted (gE-) by genetic manipulation. Such recombinant has been previously evaluated in its potential as a differential vaccine (gE- vaccine) that allows differentiation between vaccinated and infected animals. Here, in the first part of the present study, the safety of the gE- vaccine during pregnancy was evaluated by the intramuscular inoculation of 107.4 tissue culture 50 % infective doses (TCID50) of the virus into 22 pregnant dams (14 BoHV-1 seronegative; 8 seropositive), at different stages of gestation. Other 15 pregnant dams were kept as non-vaccinated controls. No abortions, stillbirths or fetal abnormalities were seen after vaccination. Seroconversion was observed in both groups of previously seronegative vaccinated animals. In the second part of the study, the potential of the gE- vaccine virus to spread among beef cattle under field conditions was examined. Four heifers were inoculated intranasally with a larger amount (107,6 TCID50) of the gE- vaccine (to increase chances of transmission) and mixed with other sixteen animals at the same age and body condition, in the same grazing area, at a population density equal to the average cattle farming density within the region (one cattle head per 10,000 m2), for 180 days. All animals were monitored daily for clinical signs. Serum samples were collected on days 0, 30, 60 and 180 post-vaccination. Seroconversion was observed only in vaccinated heifers. These results indicate that, under the conditions of the present study, the gE- vaccine virus did not cause any noticeable harmful effect on pregnant dams and on its offspring and did not spread horizontally among cattle.

• Bovine herpesvirus 1 BoHV-1 recombinant gE- vaccine.

Abstract in Portuguese:

Spilki F.R., Silva A.D., Batista H.B.C.R., Oliveira A.P., Winkelmann E., Franco A.C., Porciúncula J.A. & Roehe P.M. 2005. Field evaluation of safety during gestation and horizontal spread of a recombinant differential bovine herpesvirus 1 (BoHV-1) vaccine. Pesquisa Veterinária Brasileira 25(1):54-58. Instituto de Pesquisa Veterinária Desidério Finamor, Fepagro-Saúde Animal, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@ufrgs.br Bovine herpesvirus type 1 (BoHV-1) is recognized as a major cause of respiratory, reproductive disease and abortion in cattle. Vaccination is widely applied to minimize losses induced by BoHV-1 infections; however, vaccination of dams during pregnancy with modified live virus (MLV) vaccines has been occasionally associated to abortions. We have previously reported the development of a BoHV-1 recombinant virus, constructed with basis on a Brazilian BoHV-1 (Franco et al. 2002a) from which the gene coding for glycoprotein E (gE) was deleted (gE-) by genetic manipulation. Such recombinant has been previously evaluated in its potential as a differential vaccine (gE- vaccine) that allows differentiation between vaccinated and infected animals. Here, in the first part of the present study, the safety of the gE- vaccine during pregnancy was evaluated by the intramuscular inoculation of 107.4 tissue culture 50 % infective doses (TCID50) of the virus into 22 pregnant dams (14 BoHV-1 seronegative; 8 seropositive), at different stages of gestation. Other 15 pregnant dams were kept as non-vaccinated controls. No abortions, stillbirths or fetal abnormalities were seen after vaccination. Seroconversion was observed in both groups of previously seronegative vaccinated animals. In the second part of the study, the potential of the gE- vaccine virus to spread among beef cattle under field conditions was examined. Four heifers were inoculated intranasally with a larger amount (107,6 TCID50) of the gE- vaccine (to increase chances of transmission) and mixed with other sixteen animals at the same age and body condition, in the same grazing area, at a population density equal to the average cattle farming density within the region (one cattle head per 10,000 m2), for 180 days. All animals were monitored daily for clinical signs. Serum samples were collected on days 0, 30, 60 and 180 post-vaccination. Seroconversion was observed only in vaccinated heifers. These results indicate that, under the conditions of the present study, the gE- vaccine virus did not cause any noticeable harmful effect on pregnant dams and on its offspring and did not spread horizontally among cattle.

Abstract in English:

Elias F., Schild A.L. & Riet-Correa F. 2004. [Bovine herpesvirus type-5 meningoencephalitis and malacia: histological lesions distribution in the central nervous system of naturally infected cattle.] Meningoencefalite e encefalomalacia por Herpesvírus bovino-5: distribuição das lesões no sistema nervoso central de bovinos naturalmente infectados. Pesquisa Veterinária Brasileira 24(3):123-131. Laboratório Regional de Diagnóstico, Faculdade de Veterinária, UFPel, Cx. Postal 354, Pelotas, RS 96010-900, Brazil. E-mail: alschild@terra.com.br The distribution of the histological lesions in the central nervous system (CNS) of cattle naturally infected by bovine herpes virus type-5 (BHV-5) was determined in 12 affected calves from 10 outbreaks of the disease diagnosed by the Regional Diagnostic Laboratory (LRD) at Pelotas University, from 1986 to 2003. The epidemiological data, clinical signs and duration of clinical course were obtained from the files of LRD. Transversal sections were performed at different levels in 10% formalin-fixed CNS. The sections were made in the frontal, parietal, temporal e occipital lobes of the telencephalic hemispheres, basal ganglia and internal capsule, thalamus, anterior colliculus, pons, cerebellar peduncles, cerebellum, medulla oblongata and cervical spinal cord. Paraffin embedded tissues were sectioned and stained with hematoxylin and eosin. The severity and distribution of the inflammatory and malacic lesions were evaluated in all sections. These lesions were related with the epidemiological and clinical aspects of the disease. The outbreaks of the disease were observed in different seasons of the year. Affected animals were 2 to 24-month-old, of different breeds and both sexes. Gross lesions characterized by yellow and depressed areas in the cerebral cortex were observed in five calves. In two of them, similar lesions were additionally observed in thalamus, basal nuclei, and internal capsule. Congestion and multifocal hemorrhages were observed in most cases. The histological lesions were characterized by non-suppurative meningoencephalitis in all sections of CNS, but more severe in the frontal cortex. Focal or widespread malacia with infiltration of Gitter cells were observed in all sections of cerebral cortex, basal ganglia, internal capsule, and thalamus. In some cases mild malacia was also observed in the rostral colliculi, pons, medulla, cerebellum and cervical spinal cord. Intranuclear inclusion bodies were seen in all cases studied; they were frequent in regions of the cerebral cortex near mild to moderate inflammatory or malacic lesions. In two cases the inclusion bodies were also seen in the basal ganglia and thalamus. The severity of the histological lesions was not proportional with the clinical course of the disease. The presence of lesions of malacia in different regions of the CNS, an aspect not mentioned in most reports of BHV-5 infections, could be due to variable pathogenicity of different virus isolates. Alternatively, it is possible that BHV-5 encephalitis occurs due to the reactivation of the virus in cattle previously affected by polioencefalomacia; this last sequence of events was already demonstrated experimentally by our research group.

• Bovine herpesvirus type-5 BHV-5 cattle meningoencephalitis polioencephalomalacia.

Abstract in Portuguese:

Elias F., Schild A.L. & Riet-Correa F. 2004. [Bovine herpesvirus type-5 meningoencephalitis and malacia: histological lesions distribution in the central nervous system of naturally infected cattle.] Meningoencefalite e encefalomalacia por Herpesvírus bovino-5: distribuição das lesões no sistema nervoso central de bovinos naturalmente infectados. Pesquisa Veterinária Brasileira 24(3):123-131. Laboratório Regional de Diagnóstico, Faculdade de Veterinária, UFPel, Cx. Postal 354, Pelotas, RS 96010-900, Brazil. E-mail: alschild@terra.com.br The distribution of the histological lesions in the central nervous system (CNS) of cattle naturally infected by bovine herpes virus type-5 (BHV-5) was determined in 12 affected calves from 10 outbreaks of the disease diagnosed by the Regional Diagnostic Laboratory (LRD) at Pelotas University, from 1986 to 2003. The epidemiological data, clinical signs and duration of clinical course were obtained from the files of LRD. Transversal sections were performed at different levels in 10% formalin-fixed CNS. The sections were made in the frontal, parietal, temporal e occipital lobes of the telencephalic hemispheres, basal ganglia and internal capsule, thalamus, anterior colliculus, pons, cerebellar peduncles, cerebellum, medulla oblongata and cervical spinal cord. Paraffin embedded tissues were sectioned and stained with hematoxylin and eosin. The severity and distribution of the inflammatory and malacic lesions were evaluated in all sections. These lesions were related with the epidemiological and clinical aspects of the disease. The outbreaks of the disease were observed in different seasons of the year. Affected animals were 2 to 24-month-old, of different breeds and both sexes. Gross lesions characterized by yellow and depressed areas in the cerebral cortex were observed in five calves. In two of them, similar lesions were additionally observed in thalamus, basal nuclei, and internal capsule. Congestion and multifocal hemorrhages were observed in most cases. The histological lesions were characterized by non-suppurative meningoencephalitis in all sections of CNS, but more severe in the frontal cortex. Focal or widespread malacia with infiltration of Gitter cells were observed in all sections of cerebral cortex, basal ganglia, internal capsule, and thalamus. In some cases mild malacia was also observed in the rostral colliculi, pons, medulla, cerebellum and cervical spinal cord. Intranuclear inclusion bodies were seen in all cases studied; they were frequent in regions of the cerebral cortex near mild to moderate inflammatory or malacic lesions. In two cases the inclusion bodies were also seen in the basal ganglia and thalamus. The severity of the histological lesions was not proportional with the clinical course of the disease. The presence of lesions of malacia in different regions of the CNS, an aspect not mentioned in most reports of BHV-5 infections, could be due to variable pathogenicity of different virus isolates. Alternatively, it is possible that BHV-5 encephalitis occurs due to the reactivation of the virus in cattle previously affected by polioencefalomacia; this last sequence of events was already demonstrated experimentally by our research group.

Abstract in English:

Spilki F.R, Esteves P.A., Lima M., Franco A.C., Chiminazzo C., Flores E.F., Weiblen R., Driemeier D. & Roehe P.M. 2004. Comparative pathogenicity of bovine herpesviruses type 1 (BHV-1) subtypes 1 (BHV-1.1) and 2a (BHV-1.2a). Pesquisa Veterinária Brasileira 24(1):43-49. Centro de Pesquisas Desidério Finamor, Fepagro Saúde Animal, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@ufrgs.br The study aimed to examine the capacity of two bovine herpesvirus type 1 (BHV-1) isolates of different subtypes (EVI 123/96, BHV-1.1; SV265/98, BHV-1.2a) to induce respiratory disease in calves. These two isolates are representative of the BHV-1 subtypes prevalent in Brazil. Viral subtypes were confirmed by monoclonal antibody analysis and by restriction enzyme digestion of viral genomes. The viruses were inoculated intranasally into seven 3 months old calves (four with BHV-1.1, three with BHV-1.2a). Three other calves of identical age and condition were kept as uninfected controls. In both groups of infected calves, the clinical signs observed were consistent with typical infectious bovine rhinothracheitis (IBR), including pyrexia, apathy, anorexia, nasal and ocular mucopurulent discharges, erosions on the nasal mucosa, conjunctivitis, lachrymation, redness of nasal mucosa, dyspnoea, coughing, tracheal stridor and enlargement of retropharingeal, submandibular and cervical lymphnodes. No significant differences were observed between the clinical scores attributed to both groups. Virus shedding in nasal and ocular secretions were also similar, apart from a significant difference in nasal virus shedding on day 1 to 3 post-inoculation, which was higher for BHV-1.1 than for BHV-1.2a. Following corticosteroid induced reactivation of the latent infection, recrudescence of clinical signs was also observed, with no significant differences on both groups. It was concluded that both subtypes BHV-1.1 and BHV-1.2a were able to induce clinically undistinguishable respiratory disease in calves, either subsequent to a primary infection or following reactivation.

• Infectious bovine rhinotracheitis IBR BHV-1.1 BHV-1.2a subtypes pathogenicity.

Abstract in Portuguese:

Spilki F.R, Esteves P.A., Lima M., Franco A.C., Chiminazzo C., Flores E.F., Weiblen R., Driemeier D. & Roehe P.M. 2004. Comparative pathogenicity of bovine herpesviruses type 1 (BHV-1) subtypes 1 (BHV-1.1) and 2a (BHV-1.2a). Pesquisa Veterinária Brasileira 24(1):43-49. Centro de Pesquisas Desidério Finamor, Fepagro Saúde Animal, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@ufrgs.br The study aimed to examine the capacity of two bovine herpesvirus type 1 (BHV-1) isolates of different subtypes (EVI 123/96, BHV-1.1; SV265/98, BHV-1.2a) to induce respiratory disease in calves. These two isolates are representative of the BHV-1 subtypes prevalent in Brazil. Viral subtypes were confirmed by monoclonal antibody analysis and by restriction enzyme digestion of viral genomes. The viruses were inoculated intranasally into seven 3 months old calves (four with BHV-1.1, three with BHV-1.2a). Three other calves of identical age and condition were kept as uninfected controls. In both groups of infected calves, the clinical signs observed were consistent with typical infectious bovine rhinothracheitis (IBR), including pyrexia, apathy, anorexia, nasal and ocular mucopurulent discharges, erosions on the nasal mucosa, conjunctivitis, lachrymation, redness of nasal mucosa, dyspnoea, coughing, tracheal stridor and enlargement of retropharingeal, submandibular and cervical lymphnodes. No significant differences were observed between the clinical scores attributed to both groups. Virus shedding in nasal and ocular secretions were also similar, apart from a significant difference in nasal virus shedding on day 1 to 3 post-inoculation, which was higher for BHV-1.1 than for BHV-1.2a. Following corticosteroid induced reactivation of the latent infection, recrudescence of clinical signs was also observed, with no significant differences on both groups. It was concluded that both subtypes BHV-1.1 and BHV-1.2a were able to induce clinically undistinguishable respiratory disease in calves, either subsequent to a primary infection or following reactivation.

Abstract in English:

ABSTRACT.- Spilki F.R., Franco A.C., Teixeira M.B., Esteves P.A., Schaefer R., Schmidt E., Lemos R.A. & Roehe P.M. 2003. Bovine herpesvirus type 5 (BHV-5) in a calf with rabies. Pesquisa Veterinária Brasileira 23(1):1-4. Centro de Pesquisas Veterinárias Desidério Finamor, FepagroSaúde Animal, Cx. Postal 2076, Porto Alegre, RS 90001-970, Brazil. The brain of an one year old mal e calf which died with signs of neurological disease was submitted to the laboratory for rabies diagnosis. Microscopical findings included moderate mielitis, mild meningoencephalitis with perivascular cell cuffing and Negri inclusion bodies in Purkinje cells of the cerebellum. Rabies virus infection was further confirmed by the direct fluorescent antibody test as well as by mouse inoculation. ln addition, a herpesvirus was isolated from brain tissues. The isolate was antigenic and genetically characterized as bovine herpesvirus type 5 (BHV-5). It was not possible to determine whether BHV-5 played an active role in the outcome of the infection, since, the virus might have been present in a latent form in neural tissues. This is the first report of a mixed rabies/ BHV-5 infection in calves.

• Bovine herpesvirus type 5 BHV-5 rabies Herpesvírus bovino tipo 5 raiva.

Abstract in Portuguese:

RESUMO.- Spilki F.R., Franco A.C., Teixeira M.B., Esteves P.A., Schaefer R., Schmidt E., Lemos R.A. & Roehe P.M. 2003. Bovine herpesvirus type 5 (BHV-5) in a calf with rabies. Pesquisa Veterinária Brasileira 23(1):1-4. [Herpesvírus bovino tipo 5 (BHV-5) em bovino infectado pelo vírus da raiva.] Centro de Pesquisas Veterinárias Desidério Finamor, FepagroSaúde Animal, Cx. Postal 2076, Porto Alegre, RS 90001-970, Brazil. O encéfalo de um bezerro macho, de um ano de idade, que morreu com sinais de doença neurológica, foi submetido ao laboratório para diagnóstico de raiva. O exame histopatológico revelou mielite moderada, meningoencefalite leve com infiltração perivascular e corpúsculos de Negri nas células de Purkinje do cerebelo. A infecção pelo vírus rábico foi ainda confirmada por imunofluorescência diretá e por inoculação em camundongos. Além disso, um herpesvírus foi isolado dos tecidos do encéfalo. O vírus isolado foi antigênica e geneticamente caracterizado como Herpesvírus bovino tipo 5 (BHV-5). Não foi possível determinar se o BHV-5 teve algum papel ativo no desfecho da enfermidade, uma vez que o vírus poderia estar presente em forma latente nos tecidos neurais. Este é o primeiro relato de uma infecção mista pelo vírus da raiva e BHV-5 em bovinos.

Abstract in English:

ABSTRACT.- Franco A.C., Spilki F.R., Esteves P.A., Lima M., Weiblen R., Flores E.F., Rijsewijk F.A.M. & Roehe P.M. 2002. A Brazilian glycoprotein E-negative bovine herpesvirus type 1.2a (BHV-1.2a) mutant is attenuated for cattle and induces protection against wild-type virus challenge. Pesquisa Veterinária Brasileira 22(4):135-140. [Um mutante gE-negativo de herpesvírus bovino tipo 1.2a é atenuado para bovinos e induz proteção frente ao desafio com vírus de campo.] Centro de Pesquisas Veterinárias Desidério Finamor, Fepagro-Saúde Animal, Cx. Postal 2076, Porto Alegre, RS 90001-970, Brazil. E-mail: proehe@ufrgs.br The authors previously reported the construction of a glycoprotein E-deleted (gE·) mutante of bovine herpesvirus type 1.2a (BHV-1.2a). This mutant, 265gE·, was designed as a vacinal strain for differential vaccines, allowing the distinction between vaccinated and naturally infected cattle. In order to determine the safety and efficacy of this candidate vaccine virus, a group of calves was inoculated with 265gE·. The virus was detected in secretions of inoculated calves to lower titres and for a shorter period than the parental virus inoculated in control calves. Twenty one days after inoculation, the calves were challenged with the wild type parental virus. Only mild signs of infection were detected on vaccinated calves, whereas nonvaccinated controls displayed intense rhinotracheitis and shed virus for longer and to higher titres than vaccinated calves. Six months after vaccination, both vaccinated and control groups were subjected to reactivation of potentially latent virus. The mutant 265gE· could not be reactivated from vaccinated calves. The clinical signs observed, following the reactivation of the parental virus, were again much milder on vaccinated than on non-vaccinated calves. Moreover, parental vírus shedding was considerably reduced on vaccinated calves at reactivation. In view of its attenuation, immunogenicity and protective effect upon challenge and reactivation with a virulent BHV-1, the mutant 265gE· was shown to be suitable for use as a BHV-1 differential vaccine vírus.

• BHV-1 differential vaccine gE deletion IBR vacina diferencial gE.

Abstract in Portuguese:

RESUMO.- Franco A.C., Spilki F.R., Esteves P.A., Lima M., Weiblen R., Flores E.F., Rijsewijk F.A.M. & Roehe P.M. 2002. A Brazilian glycoprotein E-negative bovine herpesvirus type 1.2a (BHV-1.2a) mutant is attenuated for cattle and induces protection against wild-type virus challenge. Pesquisa Veterinária Brasileira 22(4):135-140. [Um mutante gE-negativo de herpesvírus bovino tipo 1.2a é atenuado para bovinos e induz proteção frente ao desafio com vírus de campo.] Centro de Pesquisas Veterinárias Desidério Finamor, Fepagro-Saúde Animal, Cx. Postal 2076, Porto Alegre, RS 90001-970, Brazil. E-mail: proehe@ufrgs.br Em estudo prévio os autores reportaram a construção de um mutante do Vírus da Rinotraqueíte Infecciosa Bovina (IBR) ou Herpesvírus Bovino tipo 1.2a (BHV-1.2a), do qual foi deletado o gene que codifica a glicoproteina E. Esse mutante (265gE-) foi construído a partir de uma amostra autóctone do vírus, tendo como objetivo seu uso como amostra vacinai em vacinas diferenciais, capazes de permitir a diferenciação entre animais vacinados e infectados com vírus de campo. Para determinar a atenuação e eficácia do 265gE· como imunógeno, bezerros foram inoculados por via intranasal com 106,9 DICC50 do mesmo. O vírus foi detectado em secreções dos animais inoculados em títulos mais baixos e por um período mais curto do que a amostra virulenta parental, inoculada em animais controle. Vinte e um dias após, os animais inoculados com o vírus mutante foram desafiados com a amostra parental, apresentando somente sinais leves de infecção. Os animais controle apresentaram intensa rinotraqueíte e excretaram vírus em títulos mais elevados e por mais tempo do que os vacinados. Seis meses após a vacinação, foi examinada a capacidade de reativação da infecção nos bezerros, através da administração de corticosteróides. O mutante 265gE- não foi reativado dos animais vàcinados. Os sinais clínicos consequentes à reativação do vírus parental foram muito atenuados nos animais vacinados, em comparação com os não vacinados. Além disso, a excreção de vírus de campo foi consideravelmente reduzida nestes últimos. Em vista de sua atenuação, imunogenicidade e efeito protetivo frente ao desafio com uma amostra virulenta de BHV-1 e subseqüente reativação, o mutante 265gE- demonstrou apresentar grande potencial para ser utilizado como vírus vacinai em vacinas diferenciais contra o BHV-1.

Abstract in English:

ABSTRACT.- Spilki F.R., Esteves P.A., Franco A.C., Lima M., Holz C.L., Batista H.B.C.R., Driemeier D., Flores E.F., Weiblen R. & Roehe P.M. 2002. [Neurovirulence and neuroinvasiveness of bovine herpesvirus type 1 and 5 in rabbits.] Neurovirulência e neuroinvasividade de Herpesvírus bovinos tipos 1 e 5 em coelhos. Pesquisa Veterinária Brasileira 22(2):58-63. Centro de Pesquisas Veterinárias Desidério Finamor, Estrada do Conde 6000, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@orion.ufrgs.br In order to determine the capacity of bovine herpesvirus type 1 and 5 (BHV-1 and BHV-5) to invade, multiply and spread along the central nervous system (CNS) (neuroinvasiveness), as well as their potential to induce neurological illness (neurovirulence), 30 to 35 days old rabbits were inoculated with the BHV-5 strain EVI 88 / 95 and Los Angeles and Cooper BHV-1 strains, by the intrathecal (IT) and intranasal (IN) routes. The BHV-5 strain induced severe neurological clinical signs in 100% (12/12) of the rabbits inoculated by both routes. Histopathological examination revealed multifocal non-suppurative meningoencephalitis, characterized by multifocal gliosis and perivascular cuffing. Virus was recovered from many parts of the brain. Both BHV-1 strains, when inoculated via 1T route, were not neurovirulent. The strain Los Angeles, after IN inoculation, induced signs of severe respiratory disease (7/7), as well as signs of neurological impairment, indistinguishable from those induced by BHV-5, in 57% (4/7) of the infected rabbits. However, the rabbits with nervous signs revealed at histopathology vasculitis and thrombosis in lungs and brain, the latter with foci of neuronal necrosis, but no lesions indicative of encephalitis, suggesting that neural damage was probably consequent to tissue anoxia. The BHV-1 strain Cooper, after IN inoculation, induced only mild signs of respiratory disease. These findings indicate that the BHV-5 strain was both neuroinvasive and neurovirulent, since it was capable of invading, spreading and multiplying in the rabbits brains by both routes of inoculation, yet causing neurological disease, apparently consequent to vírus induced neural damage. The BHV-1 Los Angeles strain was not neuroinvasive, whereas its neurovirulence was probably consequent to tissue anoxia, which histologically seemed not to be related to direct viral pathogenic effect. The BHV-1 strain Cooper was neither neurovirulent nor neuroinvasive for rabbits. It is possible that these observations bear relationship with the frequent association of BHV-5 with encephalitis in cattle, as opposed to BHV-1 encephalitis, which is a rare event in nature.

• Infectious bovine rhinotracheitis IBR BHV-1 bovine encephalitis herpesvirus BHV-5 Rinotraqueíte infecciosa bovina herpesvírus da encefalite bovina.

Abstract in Portuguese:

RESUMO.- Spilki F.R., Esteves P.A., Franco A.C., Lima M., Holz C.L., Batista H.B.C.R., Driemeier D., Flores E.F., Weiblen R. & Roehe P.M. 2002. [Neurovirulence and neuroinvasiveness of bovine herpesvirus type 1 and 5 in rabbits.] Neurovirulência e neuroinvasividade de Herpesvírus bovinos tipos 1 e 5 em coelhos. Pesquisa Veterinária Brasileira 22(2):58-63. Centro de Pesquisas Veterinárias Desidério Finamor, Estrada do Conde 6000, Cx. Postal 47, Eldorado do Sul, RS 92990-000, Brazil. E-mail: proehe@orion.ufrgs.br Com o objetivo de avaliar a capacidade dos herpesvírus bovinos tipos 1 e 5 (BHV-1 e BHV-5) de invadir e replicar no sistema nervoso central (SNC) (neuroinvasividade), bem como sua capacidade de induzir doença neurológica (neurovirulência), coelhos com 30 a 35 dias de idade foram inoculados com uma amostra do Herpesvírus da Encefalite Bovina (BHV-5; amostra EVI 88/95) ou com amostras de BHV-1 (Los Angeles ou Cooper), pelas vias intratecal (IT) e intranasal (IN). A inoculação da amostra de BHV-5, tanto pela via 1T como IN, induziu sinais clínicos neurológicos em 100% (12/12) dos coelhos inoculados. Os exames histopatológicos revelaram um quadro de meningoencefalite não-purulenta multifocal, caracterizada por gliose multifocal e infiltrados perivasculares. O vírus foi isolado de várias áreas do SNC desses animais. As amostras de BHV-1, quando inoculadas pela via IT, não foram neurovirulentas. A amostra Los Angeles de BHV-1, quando administrada pela via IN, induziu sinais respiratórios severos, além de sinais neurológicos em 57% (4/7) dos animais inoculados. Entretanto, o exame histopatológico destes quatro animais revelou vasculite e trombose no pulmão e cérebro, este último apresentando focos de necrose neuronal, porém sem lesões indicativas de encefalite. Isso sugere que os sinais neurológicos foram, provavelmente, consequentes a prejuízos no fluxo sangüíneo encefálico, e não a danos neuronais provocados pela inoculação desse vírus. A amostra Cooper de BHV-1, quando inoculada pela via IN, induziu apenas sinais leves de infecção respiratória. Estes resultados indicam que apenas a amostra de BHV-5 foi capaz de invadir e replicar no encéfalo dos coelhos quando inoculada tanto por via IN como IT, apresentando neuroinvasividade e neurovirulência. É possível que estas observações tenham relação com o fato de amostras de BHV-5 freqüentemente causarem encefalites, em contraposição a infecções pelo BHV-1, onde encefalites são raramente observadas.