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Although canine circovirus (CanineCV)-associated with gastroenteritis has been well documented, the virus is also detectable in the respiratory discharge of dogs with respiratory disease. In this study, an epidemiological approach was used to explore the association between the presence of CanineCV and respiratory symptoms in dogs. Respiratory swabs were collected from 76 healthy dogs and 114 dogs with respiratory illness and tested for CanineCV using conventional PCR (cPCR). Furthermore, lung tissues collected from 15 necropsied dogs showing pneumonia were tested using the real-time PCR (qPCR) and in situ hybridization (ISH) technique. A total of 8.95% (17/190) of dogs were CanineCV positive, with a significant association ( p  = 0.013) in dogs with respiratory signs. Four necropsied dogs were qPCR positive with the CanineCV-DNA labeling localized in tracheobronchial lymphoid cells (3/4), pulmonary parenchyma, capillary endothelia, and mononuclear cells harboring in alveoli (2/4). Full-length genome sequences of seven CanineCV strains were analyzed, indicating that the detected CanineCV genome clustered in the CanineCV-4 genotype. Genetic recombination was also evident in the replicase ( Rep ) gene. Although the role of CanineCV primarily affecting lung lesions could not be determined from this study, the presence of CanineCV DNA in pulmonary-associated cells indicated the potential association of the virus with canine respiratory disease; thus, linking causality must be examined in further studies.

Abstract Background Whether domestic cat hepadnavirus (DCH) infection is associated with clinical disease remains to be determined. Objectives To determine the relationship between DCH detection, hematology, serum bichemistry and liver histology in DCH-positive cats. Animals One thousand twenty-two cats in Thailand without concurrent diseases and not undergoing treatments adversely affecting the liver. Methods Retrospective cross-sectional study. Samples derived from cats with concurrent virus detection were excluded. DCH detection was determined in blood and fresh-frozen liver by quantitative polymerase chain reaction (qPCR) and further investigated in liver sections showing histological parenchymal disorders (HPD) and normal liver (HNL) using in situ hybridization (ISH). Proliferative/apoptotic activities were determined using immunohistochemistry and ISH panels. Biochemical variables and risk factors for DCH infection were investigated. Results Six hundred sixty-one (557 blood and 119 liver samples) cats were included. DCH was detected in 18.50% (103/557), 13.85% (9/65), and 3.70% (2/54) of the blood, HPD, and HNL groups, respectively. Cats with DCH revealed abnormally high activity of aspartate aminotransferase (AST) (P = .001) and alanine aminotransferase (ALT) (P < .001). Among DCH-positive HPD case 2/9 an 7/9 were acute and chronic hepatitis, of which 4/7 had hepatitis. Log viral copy number (LVCN) was positively correlated with ALT (P < .001), triglyceride (P < .001), and gamma-glutamyl transpeptidase (GGT) (P = .022). The LVCN also had a positive association with degree of hepatitis (P < .05). There was hepatocyte proliferation activity in DHC positive cats. Conclusion and Clinical Importance Domestic cat hepadnavirus infection was associated with high serum activity of liver enzymes and chronic lymphoplasmacytic hepatitis (LPH).

Background Canine circovirus (CanineCV) is a single-stranded circular DNA virus that infects domestic and wild canids in many countries. CanineCV is associated with gastroenteritis and diarrhea, respiratory disease, and generalized vasculitis leading to a fatal event. The Capsid protein (Cap) is a structural protein of the virus which has high genetic variability and plays a role in the canine immune response. In this study, we cloned the full-length CanineCV Capsid gene ( Cap ). In-silico analyses were used to explore the genomic and amino acid variability and natural selection acting on the Cap gene. The immune relevance for T-cell and B-cell epitopes was predicted by the immunoinformatic approach. Results According to the Cap gene, our results showed that CanineCV was separated into five phylogenetic groups. The obtained CanineCV strain from this study was grouped with the previously discovered Thai strain (MG737385), as supported by a haplotype network. Entropy analyses revealed high nucleotide and amino acid variability of the Capsid region. Selection pressure analysis revealed four codons at positions 24, 50, 103, and 111 in the Cap protein evolved under diversifying selection. Prediction of B-cell epitopes exhibited four consensus sequences based on physiochemical properties, and eleven peptide sequences were predicted as T-cell epitopes. In addition, the positive selection sites were located within T-cell and B-cell epitopes, suggesting the role of the host immune system as a driving force in virus evolution. Conclusions Our study provides knowledge of CanineCV genetic diversity, virus evolution, and potential epitopes for host cell immune response.

Canine bocaviruses (CBoVs) have been recognized as pathogens associated with intestinal diseases. Hematogenous spreading caused by CBoV has been documented and may potentiate the virus entry across the blood-brain barrier to initiate a brain infection. This study focused attention on CBoV detection in cases of encepahlopathy and attempted to determine its viral localization. A total of 107 dog brains that histologically exhibited encephalopathy (ED) were investigated for the presence of CBoVs using polymerase chain reaction (PCR). Thirty-three histologically normal brain samples from dogs were used as a control group (CD). CBoV-2 was detected in 15 ED dogs (14.02%) but not in CD dogs ( p = 0.02), while no CBoV-1 and -3 were detected. Among the CBoV-2 positive dogs, brain histological changes were characterized by nonsuppurative encephalitis, with inclusion body-like materials in some brains. In situ hybridization (ISH) and transmission electron microscopy (TEM) confirmed the presence of CBoV-2 viral particles in glial cells, supporting neurotropism of this virus. ISH signals were also detected in the intestines, lymphoid organs, and the heart, suggesting both enteral and parenteral infections of this virus. Whole genome characterization and evolutionary analysis revealed genetic diversity of CBoV-2 sequences and it was varying among the different countries where the virus was detected. This study points to a possible association of CBoV-2 with encephalopathy in dogs. It also highlights the genetic diversity and cellular tropism of this virus.

Canine circovirus (CanineCV) is a contagious virus that causes severe gastroenteritis, diarrhea, respiratory disease, and vasculitis, often resulting in fatality among infected dogs. In this study, a recombinant Capsid protein (rCap) of CanineCV was expressed in the Escherichia coli ( E. coli ) Rosetta (DE3) pLysS host cell, followed by affinity purification, and then analyzed by SDS-PAGE, revealing a molecular weight of approximately 31 kDa. The antigenicity of the CanineCV rCap protein was confirmed through recognition by a rabbit anti-CanineCV rCap protein polyclonal antibody (PoAb). Additionally, the reactivity and specificity of this PoAb were assessed using indirect enzyme-linked immunosorbent assay (ELISA) and Western blot analysis before applying in an immunohistochemistry (IHC), namely, immunoperoxidase detection. The immunoperoxidase assay using rabbit anti-CanineCV rCap protein PoAb demonstrated that the CanineCV Cap protein was predominantly located in immune cells, especially lymphocytes and macrophages, within the spleen, lung, tracheobronchial lymph nodes, small intestine, and kidney. Similarly, the Cap protein was also found in pneumocytes in the lung and renal tubular epithelial cells in the kidney. These findings reflected the biological activity and cell tropism of the virus. Therefore, the recombinant Cap protein and its PoAb could be used for the development of a valuable diagnostic tool for CanineCV detection.

Biting midges (Culicoides) are vectors of many pathogens of medical and veterinary importance, but their viromes are poorly characterized compared to certain other hematophagous arthropods, e.g., mosquitoes and ticks. The goal of this study was to use metagenomics to identify viruses in Culicoides from Mexico. A total of 457 adult midges were collected in Chihuahua, northern Mexico, in 2020 and 2021, and all were identified as female Culicoides reevesi. The midges were sorted into five pools and homogenized. An aliquot of each homogenate was subjected to polyethylene glycol precipitation to enrich for virions, then total RNA was extracted and analyzed by unbiased high-throughput sequencing. We identified six novel viruses that are characteristic of viruses from five families (Nodaviridae, Partitiviridae, Solemoviridae, Tombusviridae, and Totiviridae) and one novel virus that is too divergent from all classified viruses to be assigned to an established family. The newly discovered viruses are phylogenetically distinct from their closest known relatives, and their minimal infection rates in female C. reevesi range from 0.22 to 1.09. No previously known viruses were detected, presumably because viral metagenomics had never before been used to study Culicoides from the Western Hemisphere. To conclude, we discovered multiple novel viruses in C. reevesi from Mexico, expanding our knowledge of arthropod viral diversity and evolution.