Molecular confirmation of ovine herpesvirus 2-induced malignant catarrhal fever lesions in cattle from Rio Grande do Norte, Brazil / Diagnóstico molecular de herpesvírus ovino tipo 2 em surto de febre catarral malígna em bovinos do Rio Grande do Norte

Molecular findings that confirmed the participation of ovine herpesvirus 2 (OVH-2) in the lesions that were consistent with those observed in malignant catarrhal fever of cattle are described. Three mixed-breed cattle from Rio Grande do Norte state demonstrated clinical manifestations that included mucopurulent nasal discharge, corneal opacity and motor incoordination. Routine necropsy examination demonstrated ulcerations and hemorrhage of the oral cavity, corneal opacity, and lymph node enlargement. Significant histopathological findings included widespread necrotizing vasculitis, non-suppurative meningoencephalitis, lymphocytic interstitial nephritis and hepatitis, and thrombosis. PCR assay performed on DNA extracted from kidney and mesenteric lymph node of one animal amplified a product of 423 base pairs corresponding to a target sequence within the ovine herpesvirus 2 (OVH-2) tegument protein gene. Direct sequencing of the PCR products, from extracted DNA of the kidney and mesenteric lymph node of one cow, amplified the partial nucleotide sequences (423 base pairs) of OVH-2 tegument protein gene. Blast analysis confirmed that these sequences have 98-100% identity with similar OVH-2 sequences deposited in GenBank. Phylogenetic analyses, based on the deduced amino acid sequences, demonstrated that the strain of OVH-2 circulating in ruminants from the Brazilian states of Rio Grande do Norte and Minas Gerais are similar to that identified in other geographical locations. These findings confirmed the active participation of OVH-2 in the classical manifestations of sheep associated malignant catarrhal fever.

Os achados moleculares confirmaram a participação do herpesvírus ovino tipo 2 (OVH-2) nas lesões observadas em um surto de febre catarral malígna em bovinos. Três bovinos oriundos de propriedade rural de Mossoró, Rio Grande do Norte apresentaram manifestações clínicas, que incluíram secreção nasal mucopurulenta, opacidade da córnea e incoordenação motora. A necropsia revelou ulcerações e hemorragias da cavidade oral, opacidade da córnea e linfonodomegalia. Os achados histopatológicos significativos incluíam vasculite necrosante generalizada, meningoencefalite não supurativa, nefrite intersticial linfocítica, hepatite linfocítica e trombose. A PCR, realizada a partir de DNA extraído do rim e do linfonodo mesentérico de um dos animais, amplificou um produto com 423 pares de base do gene da proteína do tegumento do herpesvírus ovino 2 (OVH-2). O sequenciamento direto dos produtos da PCR e a análise pelo Blast demonstraram que o produto amplificado apresentava 98-100% de identidade com sequências do OVH-2 depositadas no GenBank. As análises filogenéticas, baseadas nas sequências deduzidas de aminoácidos demonstraram que a cepa de OVH-2 circulando em ruminantes nos estados de Rio Grande do Norte e Minas Gerais são semelhantes àquelas identificadas em outras regiões geográficas. Esses achados confirmam a participação ativa de OVH-2 nas manifestações clássicas de febre catarral maligna em ovinos.

Malignant catarrhal fever-like lesions associated with ovine herpesvirus-2 infection in young calves (Bos indicus): a case report

Infection of susceptible ruminants, including domestic cattle (Bos taurus) and American bison (Bison bison), with ovine herpesvirus-2 (OvHV-2) may provoke the fatal vasculitis and lymphoproliferative syndrome, known as malignant catarrhal fever (MCF), reported worldwide. To the best of our knowledge, this is the first report of a clinical case of MCF-like lesions associated with ovine herpesvirus-2 (OvHV-2) infection in young calves (Bos indicus) including central nervous symptoms that occurred in Três Lagoas city, Mato Grosso do Sul state, a border town near São Paulo state, Brazil. The diagnosis was based on typical histological lesions characterized by systemic lymphohistiocytic and fibrinoid vasculitis, confirmed by polymerase chain reaction and subsequent phylogenetic analysis of detected OvHV-2 sequences. This finding indicates that MCF disease is spread among herds concentrated in border areas between Mato Grosso do Sul and São Paulo states.

A Sensitive and Specific PCR/dot Blot Hybridization assay for the Detection of Ovine Herpesvirus 2, a Gamma Herpesvirus

Polymerase chain reaction (PCR) provides a powerful technique for identifying viruses and studying the homology between viral nucleic acids. However, PCR assay has limitations in its susceptibility to contamination or to enzymatic inhibitors. In order to avoid problems related to nucleic acid amplification, efforts have been made to obtain specific hybridization assays, such as dot blot hybridization (DBH). DBH has higher specificity and lower sensitivity than PCR. The aims of the present study were to develop a sensitive and specific assay for the detection of ovine herpesvirus 2 (OvHV-2), a gamma herpesvirus. PCR/DBH assay for detecting OvHV-2 DNA was developed and evaluated for its sensitivity and specificity. OvHV-2 specific primer pairs, 755/556, were used for the amplification of target DNA. When PCR product was visually detected, the limit of detection of the PCR test was 102 viral copies. For DBH, the amplified DNA with OvHV-2 specific primer pairs, 556/555, was labeled by the incorporation of digoxigenin (DIG). This DIGlabeled probe was capable of detecting 104 viral copies of purified OvHV-2 DNA by DBH. On the other hand, PCR/ DBH was more sensitive than either PCR or DBH and also very specific. The results showed that the sensitivity of PCR/DBH was higher and stronger than that of PCR and DBH alone. This PCR/DBH assay can be applied efficiently to confirm the presence of OvHV-2 virus on clinical samples and to differentiate specifically between OvHV-2 infection and other viral infections.

Application of Laser Microdissection to Identify the Cells Susceptible to Ovine Herpesvirus 2

Laser microdissection (LMD) is an important method for obtaining pure cell samples for genetic and proteomic analysis. In general, immunohistochemistry (IHC) and in situ hybridization (ISH) are useful techniques for targeting virus-specific cell populations. However, until now, there have been no IHC and ISH methods available for detecting ovine herpesvirus (OvHV-2). Previous reports have strongly suggested that lytic replication might occur in the respiratory epithelial cells of OvHV-2 infected animals. The aim of the present study was to confirm respiratory epithelial cells as the susceptible cells for the OvHV-2 by using LMD as an alternative method for localizing viral distribution. The microdissection of target cells by LMD was performed using paraffin-embedded tissues from 5 sheep with high viral copies, which were suspected as the status of reactive lytic replication, and 3 sheep with low viral copies, which were suspected as the status of latent infection. Then, OvHV-2-specific polymerase chain reaction (PCR) and real-time PCR were conducted with the extracted DNAs from the microdissected cells. Our results first demonstrate that OvHV-2 DNAs can be detected in the respiratory epithelial cells of high shedder reactive animals, from which inflammatory cells infected latently by OvHV-2 was excluded. These findings indicate that respiratory epithelial cells are susceptible to OvHV-2 and may be associated with its replication in a natural host. Also, in this study, LMD showed the possibility of wide application for the sensitive localization of low copy viral sequences within specific phenotype cells in the investigation of the role of viruses in a variety of clinical conditions.