Viral infections shared between water buffaloes and small ruminants in Switzerland

First Insights into the Occurrence of Circular Single-Stranded DNA Genomes in Asian and African Cattle

Circular replicase-encoding single-stranded (CRESS) DNA viruses and other circular DNA agents are increasingly found in various samples and animals. A specific class of these agents-termed bovine meat and milk factors (BMMF)-has been supposed to act as a factor in indirect carcinogenesis in humans. Initial observations attributed the BMMF to European cattle breeds and foodstuffs produced thereof. In the present study, blood and fecal samples from African and Asian cattle were examined. BMMF molecules and genomoviruses were detected in all bovids under study. The majority (79%) of the 29 circular elements could be assigned to BMMF groups 1 and 2, whereas CRESS viruses of the family Genomoviridae accounted for the smaller part (21%). Two genomoviruses belong to the genus Gemykibivirus and one to the genus Gemykrogvirus. The remaining three might be considered as novel species within the genus Gemycircularvirus. The majority of all isolated molecules originated from fecal samples, whereas only three derived from blood. The results from this study expand our knowledge on the diversity and presence of circular DNA in different ruminants that serve for food production in many countries over the world.

Possible Association of Bovine Gammaherpesvirus 6 with Pulmonary Disease in a Cow

Bovine gammaherpesvirus 6 (BoGHV6), previously known as bovine lymphotropic virus, is a member of the Macavirus genus, subfamily Gammaherpesvirinae. Other members of the genus Macavirus include viruses that produce malignant catarrhal fever (MCF) in mammalian hosts, collectively referred to as the MCF virus (MCFV) complex, and the porcine lymphotropic herpesvirus (PLHV). However, the current role of BoGHV6 in the development of diseases and/or disease syndromes remains uncertain and controversial. This paper investigated the participation of BoGHV6 in the development of pulmonary disease in a cow with interstitial pneumonia by histopathology and molecular testing. Tissue antigens of common viral agents of respiratory diseases and Mycoplasma bovis were not identified by immunohistochemistry. Additionally, molecular assays designed to amplify common bacterial and viral pathogens of pulmonary disease did not amplify the nucleic acids of these agents. However, a pan-PCR assay amplified the DNA of the herpesvirus polymerase gene, while the specific BoGHV6 nested-PCR assay amplified the partial fragment of the BoGHV6 polymerase gene derived from the pulmonary tissue with interstitial pneumonia. Phylogenetic analysis revealed that the BoGHV6 strain herein identified had 99.8% nucleotide (nt) sequence identity with reference strains of BoGHV6, but only 72.2-73.5% and 67.9-68.6% nt identity with reference strains of MCFV and PLHV, respectively. Consequently, these results suggest that BoGHV6 was associated with the pulmonary disease observed in this cow.

Molecular Tools to Identify and Characterize Malignant Catarrhal Fever Viruses (MCFV) of Ruminants and Captive Artiodactyla

The family Herpesviridae includes viruses identified in mammals, birds and reptiles. All herpesviruses share a similar structure, consisting of a large linear double-stranded DNA genome surrounded by a proteic icosahedral capsid further contained within a lipidic bilayer envelope. The continuous rise of genetic variability and the evolutionary selective pressure underlie the appearance and consolidation of novel viral strains. This applies also to several gamma(γ)-herpesviruses, whose role as primary pathogen has been often neglected and, among these to newly emerged viruses or virus variants responsible for the development of Malignant Catarrhal Fever (MCF) or MCF-like disease. The identification of γ-herpesviruses adapted to new zoological hosts requires specific molecular tools for detection and characterization. These viruses can cause MCF in livestock and wild animals, a disease generally sporadic but with serious welfare implications and which, in many cases, leads to death within a few days from the appearance of the clinical signs. In the absence of a vaccine, the first step to improve disease control is based on the improvement of molecular tools to identify and characterize these viruses, their phylogenetic relationships and evolutionary interaction with the host species. A Panherpes PCR-specific test, based on the conserved DNA polymerase gene, employing consensus/degenerate and deoxyinosine-substituted primers followed by sequencing, is still the preferred diagnostic test to confirm and characterize herpesviral infections. The drawback of this test is the amplification of a relatively short sequence, which makes phylogenetic analysis less stringent. Based on these diagnostic requirements, and with a specific focus on γ-herpesviruses, the present review aims to critically analyze the currently available methods to identify and characterize novel MCFV strains, to highlight advantages and drawbacks and to identify the gaps to be filled in order to address research priorities. Possible approaches for improving or further developing these molecular tools are also suggested.

Identification and Characterization of Circular Single-Stranded DNA Genomes in Sheep and Goat Milk

In recent years, a variety of circular replicase-encoding single-stranded (CRESS) DNA viruses and unclassified virus-like DNA elements have been discovered in a broad range of animal species and environmental samples. Key questions to be answered concern their presence in the human diet and their potential impact on disease emergence. Especially DNA elements termed bovine meat and milk factors (BMMF) are suspected to act as co-factors in the development of colon and breast cancer. To expand our knowledge on the occurrence of these potential pathogens in human nutrition, a total of 73 sheep and 40 goat milk samples were assayed by combining rolling circle amplification (RCA), PCR and Sanger sequencing. The present study further includes retail milk from the aforementioned species. We recovered 15 single stranded (ss) circular genomes. Of those, nine belong to the family Genomoviridae and six are members of the unclassified group of BMMF. Thus, dairy sheep and goats add to dispersal of CRESS viruses and circular ssDNA elements, which enter the food chain via milk. The presence of these entities is therefore more widespread in Bovidae than initially assumed and seems to be part of the common human nutrition.