Feline bocavirus-1 associated with outbreaks of hemorrhagic enteritis in household cats: potential first evidence of a pathological role, viral tropism and natural genetic recombination

Epidemiology and genotypic diversity of feline bocavirus identified from cats in Harbin, China

Feline bocavirus (FBoV) is a globally distributed linear, single-stranded DNA virus infect cats, currently classified into three distinct genotypes. Although FBoV can lead to systemic infections, its complete pathogenic potential remains unclear. In this study, 289 blood samples were collected from healthy cats in Harbin, revealing an overall FBoV prevalence of 12.1%. Notably, genotypes 1 and 3 of FBoV were found co-circulating among the cat population in Harbin. Additionally, recombination events were detected, particularly in the newly discovered NG/104 and DL/102 strains. Furthermore, negative selection sites were predominantly observed across the protein coding genes of FBoV. These findings suggest a co-circulation of genetically diverse FBoV strains among cats in Harbin, indicate that purifying selection is the primary driving force shaping the genomic evolution of FBoV, and also underscore the importance of comprehensive surveillance efforts to enhance our understanding of the epidemiology and evolutionary characteristics of FBoV.

Carnivore chaphamaparvovirus-1 (CaChPV-1) infection in diarrheic dogs reveals viral endotheliotropism in intestine and lung

BACKGROUND

Carnivore chaphamaparvovirus-1 (CaChPV-1) is a parvovirus identified in dogs and association of infection with diarrhea is controversial. Information on whether tissue tropism persists is lacking.

OBJECTIVES

To determine the disease association of CaChPV-1 in dogs with diarrhea and to investigate viral tropism and genetic diversity.

ANIMALS AND METHODS

CaChPV-1 infection was investigated in five recently deceased puppies and designed a retrospective study to determine whether the presence of CaChPV-1 is associated with diarrhea. The retrospective study was conducted in 137 intestinal tissue samples and 168 fecal samples obtained from 305 dogs. CaChPV-1 tissue localization was determined using in situ hybridization, and CaChPV-1 complete genomes obtained from dead puppies and retrospective study were sequenced and analyzed.

RESULTS

CaChPV-1 was detected in 6.56% (20/305) of tested dogs, including 14 diarrheic- and 6 non-diarrheic dogs, and was significant in puppies with diarrhea (p = 0.048). Among the CaChPV-1-positive diarrheic dogs, one sample was obtained from intestinal tissue and 13 samples were fecal samples. However, six CaChPV-1 positive non-diarrheic dogs were based on fecal samples but not on intestinal tissue. Within the age range, the presence of CaChPV-1 was significant in puppies (p < 0.00001) and was mainly localized in the stromal and endothelial cells of intestinal villi and pulmonary alveoli. Phylogenetic analysis indicated genetic diversity of CaChPV-1 Thai strains that were mostly clustered within the sequences found in China.

CONCLUSIONS

Although definitive pathogenesis of CaChPV-1 remains undetermined, this study provides evidence supporting that CaChPV-1 localizes in canine cells and could play a potential role as an enteric pathogen.

Exploring the Enteric Virome of Cats with Acute Gastroenteritis

Viruses are a major cause of acute gastroenteritis (AGE) in cats, chiefly in younger animals. Enteric specimens collected from 29 cats with acute enteritis and 33 non-diarrhoeic cats were screened in PCRs and reverse transcription (RT) PCR for a large panel of enteric viruses, including also orphan viruses of recent identification. At least one viral species, including feline panleukopenia virus (FPV), feline enteric coronavirus (FCoV), feline chaphamaparvovirus, calicivirus (vesivirus and novovirus), feline kobuvirus, feline sakobuvirus A and Lyon IARC polyomaviruses, was detected in 66.1% of the samples.. Co-infections were mainly accounted for by FPV and FCoV and were detected in 24.2% of the samples. The virome composition was further assessed in eight diarrhoeic samples, through the construction of sequencing libraries using a sequence-independent single-primer amplification (SISPA) protocol. The libraries were sequenced on Oxford Nanopore Technologies sequencing platform. A total of 41 contigs (>100 nt) were detected from seven viral families infecting mammals, included Parvoviridae, Caliciviridae, Picornaviridae, Polyomaviridae, Anelloviridae, Papillomaviridae and Paramyxoviridae, revealing a broad variety in the composition of the feline enteric virome.

Old and Novel Enteric Parvoviruses of Dogs

Parvovirus infections have been well known for around 100 years in domestic carnivores. However, the use of molecular assays and metagenomic approaches for virus discovery and characterization has led to the detection of novel parvovirus species and/or variants in dogs. Although some evidence suggests that these emerging canine parvoviruses may act as primary causative agents or as synergistic pathogens in the diseases of domestic carnivores, several aspects regarding epidemiology and virus-host interaction remain to be elucidated.

Development of a TaqMan-based multiplex real-time PCR for simultaneous detection of four feline diarrhea-associated viruses

Since their recent discovery, the prevalence of novel feline enteric viruses, including feline bocavirus 1 (FBoV-1), feline astrovirus (FeAstV), and feline kobuvirus (FeKoV), has been reported in China. Co-infections of these viruses with feline parvovirus (FPV) are common causes of diarrhea in cats. Viral co-infections are difficult to identify because of their non-specific clinical signs. To detect and identify these viruses, a quick and specific pathogen-testing approach is required. Here, we establish a real-time PCR (qPCR) based on multiple TaqMan probes for the simultaneous detection of FBoV-1, FeAstV, FeKoV, and FPV. Specific primers and TaqMan fluorescent probes were designed to ensure specificity. The results showed that the detection limit of single qPCR was up to 10 copies, and the detection limit of multiplex qPCR was up to 100 copies, with correlation coefficients >0.995 in all cases. Clinical sample detection revealed a 25.19% (34/135) total rate of co-infection among the viruses and a 1.48% (2/135) quadruple infection rate. Thus, this multiplex qPCR approach can serve as a quick, sensitive, and specific diagnostic tool for FBoV-1, FeAstV, FeKoV, and FPV identification, and it may be utilized for routine surveillance of these emerging and reemerging feline enteric viruses.

Small but mighty: old and new parvoviruses of veterinary significance

In line with the Latin expression "sed parva forti" meaning "small but mighty," the family Parvoviridae contains many of the smallest known viruses, some of which result in fatal or debilitating infections. In recent years, advances in metagenomic viral discovery techniques have dramatically increased the identification of novel parvoviruses in both diseased and healthy individuals. While some of these discoveries have solved etiologic mysteries of well-described diseases in animals, many of the newly discovered parvoviruses appear to cause mild or no disease, or disease associations remain to be established. With the increased use of animal parvoviruses as vectors for gene therapy and oncolytic treatments in humans, it becomes all the more important to understand the diversity, pathogenic potential, and evolution of this diverse family of viruses. In this review, we discuss parvoviruses infecting vertebrate animals, with a special focus on pathogens of veterinary significance and viruses discovered within the last four years.

First detection of feline bocaparvovirus 2 and feline chaphamaparvovirus in healthy cats in Turkey

The pet cat’s population and the number of viruses that infect them are increasing worldwide. Recently, feline chaphamaparvovirus (FeChPV, also called fechavirus) and feline bocaparvovirus (FBoV) infections, which are novel parvovirus species, have been reported in cats from different geographic regions. Here, we investigated FBoV 1–3 and FeChPVs in healthy cats in Turkey using PCR, where nuclear phosphoprotein 1 (NP1) is targeted for FBoV and NP for FeChPV. For this purpose, oropharygeal swabs were obtained from 70 healthy cats with different housing status from June 15 to December 1, 2020. After PCR screening tests, six out of 70 cats (5/47 shelter cats; 1/23 domestic cats) were found to be positive for FBOV, while two were positive for FeChPV (1/47 shelter cats; 1/23 domestic cats). No cat was found in which both viruses were detected. The nucleotide (nt) sequence comparison in the 310 base pair (bp) NP gene of the two FeChPVs identified in this study shared a high identity with each other (95.0% nt and 99% aa identities) and with previously reported FeChPVs (92.4–97.1% nt and 98.1–99.0% aa identities), including 313R/2019/ITA, 49E/2019/ITA, VRI_849, 284R/2019/ITA, and IDEXX-1. Here, the near-full length (1489 nt, 495 amino acids-aa) of the VP2 gene of the FechaV/Tur-2020/68 isolate obtained from the study was also sequenced. The nt and aa identity ratio of this isolate with other FeChPVs was 98.0–98.5%-96–96.5%, respectively. Sequences of the 465 bp NP1 gene of the six Turkish FBoV strains shared high identities with each other (99.6–100% nt and 99.3–100% aa identities) and with those of FBoV-2 strains (97.8–99.1% nt and 98.0–100% aa identities), including 16SY0701, 17CC0505-BoV2, HFXA-6, and POR1. All FBoVs detected in this study were classified as genotype 2, similar to the study conducted in Japan and Portugal. Here, the NS1 (partial), NP1, VP1 and VP2 gene of the FBoV-2/TUR/2020–14 strain obtained from the study were also sequenced and the nt and aa sequences showed high identities to the above-mentioned FBoV-2 strain/isolates (> 96%, except for the aa ratio of strain 16SY0701). In conclusion, this study shows that FBoV and FeChPV are present in healthy cats in Turkey, and these viruses can be detected from oropharyngeal swabs. Our findings contribute to further investigation of the prevalence, genotype distribution, and genetic diversity of Turkish FBoVs and FeChPVs, adding to the molecular epidemiology of FBoV and FeChPVs worldwide.

Molecular and Pathological Investigations of Selected Viral Neuropathogens in Rabies-Negative Brains of Cats and Dogs Revealed Neurotropism of Carnivore Protoparvovirus-1

Throughout the year, the Thai Red Cross Society (TRCS), Bangkok, Thailand, received more than 100 animals that died of suspected rabies due to neurological clinical signs. Concerning the role of viral infection in the brain in the outcome of neurological diseases in cats and dogs, a comprehensive study was conducted of 107 brain samples of cats and dogs submitted to the TRCS from August 2019 to August 2020. Selective molecular screening using conventional polymerase chain reaction (PCR) and reverse transcription PCR targeting nine viral pathogens was employed in addition to histopathological investigations. The results showed that carnivore protoparvovirus-1 (CPPV-1) was detected in 18.69% of the cats and dogs sampled (20/107). These results were found in young and old animals; the brain tissue did not show any pathological changes suggesting encephalitis or cerebellar hypoplasia. In addition, feline calicivirus, feline alphaherpesvirus-1, feline coronavirus, and canine distemper virus were also detected, providing a broader range of potential viral infections to consider in the clinical manifestation of neurological disorders in companion animals. The detection of all pathogens was confirmed by the localization of each viral antigen in various resident brain cells using immunohistochemistry. A unique L582S amino acid substitution of the non-structural protein 1 gene coding sequence, speculated to be associated with the neurotropism of CPPV-1 in cats and dogs, was not evident. In conclusion, this study revealed a noteworthy neurotropism of CPPV-1 in both cats and dogs without neurological lesions.

Simultaneous detection of feline parvovirus and feline bocavirus using SYBR Green I-based duplex real-time polymerase chain reaction

Since both feline parvovirus (FPV) and feline bocavirus (FBoV) can cause diarrhea in cats, it is difficult to distinguish them clinically. This study aimed to develop a SYBR Green I-based duplex real-time polymerase chain reaction (PCR) assay for distinguishing FPV and FBoV-1 on the basis of the melting temperature of the PCR product. A total of 132 fecal samples from different domestic and feral cats were collected, and the results of SYBR Green I-based duplex real-time PCR assay were compared with those of the traditional PCR assay for a comprehensive evaluation. The melting temperatures were found to be 86 °C and 77.5 °C for FBoV-1 and FPV, respectively, and no specific melting peaks for other non-targeted feline viruses were observed. The data obtained from this assay had a good linear relationship; the detection limits of FPV and FBoV-1 were 2.907 × 10¹ copies/μL and 3.836 × 10¹ copies/μL, respectively. In addition, the experiment exhibited high reproducibility. The positive detection rates of the SYBR Green I-based duplex real-time PCR assay for FPV and FBoV-1 were 16.67% (22/132) and 6.82% (9/132), respectively, and the positive detection rate for co-infection with FPV and FBoV-1 was 3.03% (4/132). This result was much more sensitive than that of the traditional PCR method. Thus, the developed SYBR Green I-based assay is a sensitive, rapid, specific, and reliable method for the clinical diagnosis of FPV and FBoV-1 and can provide technical support for the simultaneous detection of co-infection with these viruses in the future.

Canine bocavirus-2 infection and its possible association with encephalopathy in domestic dogs

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.

Japanese encephalitis virus infection in meerkats (Suricata suricatta)

Japanese encephalitis virus (JEV) infection has been recognized as a serious disease in humans. Wildlife animal infections due to JEV have not been well described. This study identified JEV infection in two deceased meerkats in Thailand, with clinical signs of neurological disease. Histopathology of brains revealed severe lymphoplasmacytic necrotizing meningoencephalitis, while similar inflammation was observed in the lung and liver. Partial JEV sequences were identified from the formalin-fixed paraffin-embedded-derived brain sections of two meerkats and were found to be genetically similar to a JEV strain detected in China but not from a local strain. Using immunohistochemistry, the virus was identified in neurons and glial cells, and also found in bronchial glands, Kupffer's cells in liver, lymphocytes in the spleen and pancreatic acini, which suggests extraneural infection. Transmission electron microscopy confirmed the presence of spheroid viral particles in the lungs. These findings may suggest that infection of extraneural organs in meerkats is similar to that described in JEV-infected humans. In conclusion, this study identified the first JEV infection in meerkats as an interesting case study. The JEV should be considered as an important differential diagnosis in meerkats with encephalitis. Further surveillance on JEV infection in meerkats and other wildlife species in a large cohort is needed in the future study.

Epizootic reptilian ferlavirus infection in individual and multiple snake colonies with additional evidence of the virus in the male genital tract

Reptilian ferlavirus, a pathogen of serious concern in snakes, has been reported in Western countries, but little is known about its prevalence in Thailand, where many snake breeding farms are located. In this study, we investigated the reptilian ferlavirus via swab samples derived from 49 diseased snakes and 77 healthy snakes as well as tissue samples taken from nine dead snakes from five independent snake farms. Using molecular detection, we found the ferlavirus in 8.16% of diseased snakes, but not in healthy snakes. Out of nine farmed snakes, eight snakes derived from four farms were found to be positive. Four complete genome sequences of the ferlavirus were successfully obtained and phylogenetically clustered to the highly pathogenic ferlavirus. Tissue tropism of the ferlavirus was identified in various epithelial cell types using the in situ hybridization technique. Interestingly, the hybridization signals were strongly labeled in the male genital tract. Transmission electron microscopy was used to support the ferlaviral localization in the male genital tract. This study provides the first evidence of ferlavirus localization in the male genital tract and contributes to the knowledge about ferlavirus epidemiology, indicating that there needs to be further awareness and elucidation regarding vertical transmission of reptilian ferlavirus.

Phylogenetic analysis and evolution of feline bocavirus in Anhui Province, eastern China

To understand the epidemic status of feline bocavirus (FBoV) in Anhui Province, eastern China, FBoV was successfully extracted from fecal samples of domestic cats, and five complete genomes were amplified in this study. Phylogenetic analysis showed that these five strains belong to three different FBoV genotypes. Recombination analysis showed that inter- and intra-genotype recombination events occurred. Selection pressure and codon usage bias analyses indicated that FBoV-1 and FBoV-3 continuously evolve toward adaptation, and selection pressure is the main factor for codon usage bias during evolution. This study provides the first molecular evidence of FBoV prevalence in eastern China, further enriching the available information on its genetics and evolutionary characteristics and providing a basis for further research on its evolution.

Emerging Parvoviruses in Domestic Cats

Parvovirus infections in cats have been well known for around 100 years. Recently, the use of molecular assays and metagenomic approaches for virus discovery and characterization has led to the detection of novel parvovirus lineages and/or species infecting the feline host. However, the involvement of emerging parvoviruses in the onset of gastroenteritis or other feline diseases is still uncertain.

Natural infection of parvovirus in wild fishing cats (Prionailurus viverrinus) reveals extant viral localization in kidneys

Carnivore protoparvovirus-1 (CPPV-1), a viral species containing feline panleukopenia virus (FPV) and canine parvovirus (CPV) variants, are widely spread among domestic and wild carnivores causing systemic fatal diseases. Wild fishing cats (Prionailurus viverrinus), a globally vulnerable species, have been found dead. Postmortem examination of the carcasses revealed lesions in intestine, spleen and kidney. CPPV-1 antigen identification in these tissues, using polymerase chain reaction (PCR) and immunohistochemistry (IHC), supported the infection by the virus. PCR- and IHC-positivity in kidney tissues revealed atypical localization of the virus while in situ hybridization (ISH) and transmission electron microscopy (TEM) with the pop-off technique confirmed the first description of viral localization in kidneys. Complete genome characterization and deduced amino acid analysis of the obtained CPPV-1 from the fishing cats revealed FPV as a causative agent. The detected FPV sequences showed amino acid mutations at I566M and M569R in the capsid protein. Phylogenetic and evolutionary analyses of complete coding genome sequences revealed that the fishing cat CPPV-1 genomes are genetically clustered to the FPV genomes isolated from domestic cats in Thailand. Since the 1970s, these genomes have also been shown to share a genetic evolution with Chinese FPV strains. This study is the first evidence of CPPV-1 infection in fishing cats and it is the first to show its localization in the kidneys. These findings support the multi-host range of this parvovirus and suggest fatal CPPV-1 infections may result in other vulnerable wild carnivores.

Feline chaphamaparvovirus in cats with enteritis and upper respiratory tract disease

Feline chaphamaparvovirus (FeChPV) is a novel parvovirus, first discovered in a multi-facility feline shelter in Canada in 2019, during an outbreak of acute gastro-enteritis (AGE) in cats, and detected at high prevalence (47.0%) in faecal samples. Whether this finding was anecdotal or similar viruses are common components of feline virome is still unclear. Also, the potential impact of this virus on feline health is uncertain. Herewith, a case-control study was performed to investigate whether this novel parvovirus may play a role as enteric pathogen, screening samples collected from cats with and without AGE signs. Furthermore, we extended the research by testing archival paired oropharyngeal and ocular samples collected from cats with or without upper respiratory tract disease (URTD). FeChPV DNA was detected at high prevalence rate (36.8%, 14/38) in clinical cases, representing the most frequently identified enteric virus, followed by feline panleukopenia parvovirus (23.7%, 9/38), feline coronavirus (5.3%, 2/38), feline kobuvirus (5.3%, 2/38) and noroviruses (5.3%, 2/38). The different prevalence rates of FeChPV between the case and control group were statistically significant, suggesting a possible association of the virus with acute gastro-enteric disease. The virus was also detected at low rate in the respiratory samples of cats with (3.3%, 6/183) or without URTD (4.3%, 6/140), although there was no significant association between FeChPV and URTD. The complete VP encoding gene was determined for five viruses and the nearly full-length genome was reconstructed for three viruses, namely 313R/2019/ITA, 284R/2019/ITA and 49E/2019/ITA. In the NS1-based tree, the Italian strains clustered tightly with the two FeChPV prototypes detected in Canada, within a monophyletic cluster related to but clearly distinct from canine chaphamaparvovirus, currently classified in the species Carnivore chaphamaparvovirus 1 (CaChPV-1).

Development of SYBR Green I-based polymerase chain reaction for feline bocavirus 1 detection

Feline bocavirus 1 (FBoV-1) may be associated with diarrhea in cats. In this study, a SYBR Green I-based quantitative polymerase chain reaction (qPCR) assay was established to detect FBoV-1. The melting curve showed a single melting peak at 83.0 ℃. The results of sensitivity showed that the detection limit of the qPCR was 3.87 × 10¹ copies/μL. Of note, the detection limit of the conventional polymerase chain reaction (cPCR) was 3.87 × 10³ copies/μL. The highest intra-assay and inter-assay coefficients of variation (CV%) were 0.98% and 1.42%, respectively. The positive detection rate of 128 clinical samples using the qPCR and the cPCR was 7.0% (9/128) and 4.7% (6/128), respectively. Taken together, these results indicated that the established qPCR assay has good sensitivity, high specificity, and good reproducibility. Therefore, it could provide support for the rapid and efficient clinical detection of FBoV-1.

Pathogenesis and immune response of Nile tilapia (Oreochromis niloticus) exposed to Tilapia lake virus by intragastric route

Tilapia lake virus (TiLV) is regarded as one of the most important pathogens in tilapia aquaculture worldwide. Despite this, little is known regarding disease pathogenesis and immune responses to infection. The main objective of this study was to investigate the tissue distribution, histopathological changes, and immune response of fish exposed to TiLV. Nile tilapia (Oreochromis niloticus) maintained at 25 ± 2 °C were challenged with TiLV via intragastric-gavage. At 0.5, 1, 3, 5, 7, 10 and 15 days post-challenge (dpc), six fish per treatment were euthanized and subjected to complete necropsy. TiLV exposed fish presented 45% cumulative mortality at the end of the study. Gross lesions included cutaneous petechiae and ecchymoses, scale losses, skin ulcers, and exophthalmia. Mild multifocal hepatocellular degeneration and necrosis was observed as early as 3 dpc occasionally accompanied by syncytial formation, intracytoplasmic inclusion bodies, and inflammatory infiltrates of lymphocytes at subsequent time points. Necrosis of epithelial cells of the gastric glands and intestinal glands was also observed as early as 5 dpc. Intestinal samples showed reactive in situ hybridization signals as early as 1 dpc. No other lesions were observed in the brain or other organs. Histological changes were associated with viral dissemination and disease progression, as evidenced by increased TiLV detection in the intestine, gills, liver and spleen. Highest TiLV abundance was detected 7 dpc in gills, intestine, and liver showing an average of 6 LOG genome equivalent per ng of total RNA. Different transcript abundance was detected for the pro-inflammatory cytokine interleukin-1β and interferon-induced myxovirus resistance protein gene in the mucosal sites (gills and intestine). Interferon regulatory transcription factor 3 transcript was more abundant in systemic organs (liver and spleen) while the expression in gills and intestine showed mixed expression at different time points. On the other hand, transforming growth factor β expression patterns differed amongst the tissues with a trend towards downregulation of the gene in liver and gills, and a trend towards upregulation in the spleen and intestine. Overall, these results demonstrate the intestinal routes as a main port of entry for TiLV, which subsequently spreads systematically throughout the fish body.

Insights into the genetic diversity, recombination, and systemic infections with evidence of intracellular maturation of hepadnavirus in cats

Hepatitis B virus (HBV) is a human pathogen of global concern, while a high diversity of viruses related to HBV have been discovered in other animals during the last decade. Recently, the novel mammalian hepadnavirus, tentatively named domestic cat hepadnavirus (DCH), was detected in an immunocompromised cat. Herein, a collection of 209 cat sera and 15 hepato-diseased cats were screened for DCH using PCR, resulting in 12.4% and 20% positivity in the tested sera and necropsied cats, respectively. Among the DCH-positive sera, a significantly high level of co-detection with retroviral infection was found, with the highest proportion being co-detection with feline immunodeficiency virus (FIV). Full-length genome characterization of DCH revealed the genetic diversity between the nine Thai DCH sequences obtained, and that they phylogenetically formed three distinct monophyletic clades. A putative DCH recombinant strain was found, suggesting a possible role of recombination in DCH evolution. Additionally, quantitative PCR was used to determine the viral copy number in various organs of the DCH-moribund cats, while the pathological findings were compared to the viral localization in hepatocytes, adjacent to areas of hepatic fibrosis, by immunohistochemical (IHC) and western blot analysis. In addition to the liver, positive-DCH immunoreactivity was found in various other organs, including kidneys, lung, heart, intestine, brain, and lymph nodes, providing evidence of systemic infection. Ultrastructure of infected cells revealed electron-dense particles in the nucleus and cytoplasm of hepatocytes, bronchial epithelial cells, and fibroblasts. We propose the intracellular development mechanism of this virus. Although the definitive roles of pathogenicity of DCH remains undetermined, a contributory role of the virus associated with systemic diseases is possible.

Feline Morbillivirus Infection Associated With Tubulointerstitial Nephritis in Black Leopards (Panthera pardus)

Feline morbillivirus (FeMV) is an emerging RNA virus in the Paramyxoviridae family that was recently discovered in domestic cats ( Felis catus). To date, 2 genotypes (FeMV-1 and FeMV-2) have been detected in cats from various countries, and FeMV-1 is recognized as a pathogen associated with nephritis. However, information regarding the pathological roles and potential transmission to other felids is limited. In this article, we describe the identification of FeMV in 2 black leopards ( Panthera pardus) in Thailand that showed severe azotemia and tubulointerstitial nephritis. Molecular analysis of the partial coding sequence of the L gene revealed that these leopard FeMV strains were genetically close to the FeMV-1 isolate from domestic Thai cats. Immunohistochemistry and immunofluorescence analyses using polyclonal IgG antibodies against the FeMV matrix (M) protein showed FeMV-M antigen in renal tubular epithelial cells. These analyses also showed infiltrating lymphocytes in the renal parenchymal lesions and in the cytoplasm of lymphoid cells residing in the spleen, suggesting viral tropism and a possible pathological role. These findings are the first evidence that indicates that the black leopard could be a possible host for FeMV infection. As for other cats, the role of FeMV as a potential cause of renal disease remains to be established. The pathogenesis of FeMV infection in black leopards, or in other wild felids, through a viral transmission mechanism warrants further investigation.

TaqMan-based real-time polymerase chain reaction assay for specific detection of bocavirus-1 in domestic cats

Feline bocavirus-1 (FBoV-1) was first discovered in Hong Kong in 2012, and studies have indicated that the virus may cause feline hemorrhagic enteritis. Currently, there is a lack of an effective and quantitative method for FBoV-1 detection. In this study, a TaqMan-based quantitative real-time PCR (qPCR) for FBoV-1 detection was established. Primers and probes were designed to target the conserved region of the FBoV-1 NS1 gene. The sensitivity analysis indicated that the minimum detection limit was 4.57 × 10¹ copies/μL. The specificity test revealed no cross-reaction with seven other common feline viruses, including the same species—FBoV-2 and FBoV-3. The sensitivity of this method was 100 times higher than that of conventional PCR (cPCR). The established method showed good repeatability, with the intra-assay and inter-assay coefficients of variation of 0.18%–1.00% and 0.27%–0.45%, respectively. Furthermore, the analysis of feline feces revealed that the detection rate by qPCR was 7.0% (9/128), whereas that by cPCR was 4.7% (6/128). In conclusion, the established qPCR assay can quantitatively detect FBoV-1 with a high sensitivity, high specificity, and good reproducibility, making it a promising technique for the clinical detection of and basic and epidemiological research on FBoV-1.

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The study establishes a TaqMan qPCR method for Feline Bocavirus-1 detection.

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The assay has high sensitivity, specificity and reliability.

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The study provides a tool that could be beneficial for clinical diagnostics of Feline Bocavirus-1 infection as well as future research on the virus.

Molecular epidemiology and genome analysis of feline morbillivirus in household and shelter cats in Thailand

Background

Feline morbillivirus (FeMV) has been discovered in domestic cats associated with tubulointerstitial nephritis, but FeMV is also detected in healthy cats. This research aimed to identify and characterize the FeMV strains detected in a Thai cat population.

Results

Two-hundred and ninety-two samples (131 urine and 161 blood) derived from 261 cats (61 sheltered and 200 household cats) were included for investigating the FeMV prevalence using real-time reverse transcription PCR. The overall prevalence of FeMV detection was 11.9% (31/261) among both samples, which accounted for 14.5% (19/131) and 7.5% (12/161) of the urine and blood samples, respectively. Among the FeMV-PCR positive cats, the FeMV-detected prevalence was insignificantly associated with healthy cats (58.1%; 18/31) or urologic cats (41.9%; 13/31). Full-length genome analysis of these FeMV-Thai strains revealed that their genomes clustered together in the FeMV-1A clade with up to 98.5% nucleotide identity. Selective pressure analysis showed that overall FeMV-1 has undergone negative selection, while positive selection sites were more frequently observed in the phosphoprotein gene.

Conclusions

The detected FeMV infections in the Thai cat population were not correlated with urologic disorders, although the virus was more detectable in urine samples. The genetic patterns among the FeMV-1 Thai strains were more consistent. A large-scale study of FeMV in Thai cat samples is needed for further elucidation.

Carnivore Protoparvovirus-1 Associated With an Outbreak of Hemorrhagic Gastroenteritis in Small Indian Civets

Carnivore protoparvovirus-1 (CPPV-1) infection has been reported frequently in both domestic and wildlife species including wild carnivores. Fifty-five captive small Indian civets (Viverricula indica), farmed for perfume production in Eastern Thailand, showed clinical signs of acute bloody diarrhea, anorexia, vomiting, circling, and seizures. The disease spread within the farm and resulted in the death of 38 of the 55 civets (69% mortality) within a month. Fecal swabs were collected from the 17 surviving civets, and necropsy was performed on 7 of the dead civets. Pathologic findings were severe hemorrhagic gastroenteritis with generalized lymphadenopathy. CPPV-1 was identified in both fecal swabs and postmortem samples by species-specific polymerase chain reaction. Further whole-gene sequencing and restriction fragment length polymorphism analysis suggested feline panleukopenia virus (FPV) as the causative agent. The viral tropism and tissue distribution were confirmed by immunohistochemistry, with immunolabeling in the cytoplasm and nucleus of small intestinal crypt epithelial cells, villous enterocytes, histiocytes in lymphoid tissues, myenteric nerve plexuses, and cerebral and cerebellar neurons. Phylogenetic analysis of civet-derived CPPV-1 indicated a genetic similarity close to the FPV HH-1/86 strain detected in a jaguar (Panthera onca) in China. To our knowledge, this mass die-off of civets is the first evidence of disease associated with CPPV-1 infection in the subfamily Viverrinae. These findings support the multi-host range of parvovirus infection and raises awareness for CPPV-1 disease outbreaks in wildlife species.

Virome of a Feline Outbreak of Diarrhea and Vomiting Includes Bocaviruses and a Novel Chapparvovirus

An unexplained outbreak of feline diarrhea and vomiting, negative for common enteric viral and bacterial pathogens, was subjected to viral metagenomics and PCR. We characterized from fecal samples the genome of a novel chapparvovirus we named fechavirus that was shed by 8/17 affected cats and identified three different feline bocaviruses shed by 9/17 cats. Also detected were nucleic acids from attenuated vaccine viruses, members of the normal feline virome, viruses found in only one or two cases, and viruses likely derived from ingested food products. Epidemiological investigation of disease signs, time of onset, and transfers of affected cats between three facilities support a possible role for this new chapparvovirus in a highly contagious feline diarrhea and vomiting disease.

Feline Parvovirus Seroprevalence Is High in Domestic Cats from Disease Outbreak and Non-Outbreak Regions in Australia

Multiple, epizootic outbreaks of feline panleukopenia (FPL) caused by feline parvovirus (FPV) occurred in eastern Australia between 2014 and 2018. Most affected cats were unvaccinated. We hypothesised that low population immunity was a major driver of re-emergent FPL. The aim of this study was to (i) determine the prevalence and predictors of seroprotective titres to FPV among shelter-housed and owned cats, and (ii) compare the prevalence of seroprotection between a region affected and unaffected by FPL outbreaks. FPV antibodies were detected by haemagglutination inhibition assay on sera from 523 cats and titres ≥1:40 were considered protective. Socioeconomic indices based on postcode and census data were included in the risk factor analysis. The prevalence of protective FPV antibody titres was high overall (94.3%), even though only 42% of cats were known to be vaccinated, and was not significantly different between outbreak and non-outbreak regions. On multivariable logistic regression analysis vaccinated cats were 29.94 times more likely to have protective FPV titres than cats not known to be vaccinated. Cats from postcodes of relatively less socioeconomic disadvantage were 5.93 times more likely to have protective FPV titres. The predictors identified for FPV seroprotective titres indicate targeted vaccination strategies in regions of socioeconomic disadvantage would be beneficial to increase population immunity. The critical level of vaccine coverage required to halt FPV transmission and prevent FPL outbreaks should be determined.