Molecular characterization of new described kobuvirus in dogs with diarrhea in China

Evolutionary dynamics of canine kobuvirus in Vietnam and Thailand reveal the evidence of viral ability to evade host immunity

Canine kobuvirus (CaKoV) is a pathogen associated with canine gastrointestinal disease (GID). This study examined 327 rectal swabs (RS), including 113 from Vietnam (46 healthy, 67 with GID) and 214 from Thailand (107 healthy and 107 with GID). CaKoV was detected in both countries, with prevalences of 28.3% (33/113) in Vietnam and 7.9% (17/214) in Thailand. Additionally, CaKoV was found in both dogs with diarrhea and healthy dogs. CaKoV was mainly found in puppies under six months of age (30.8%). Co-detection with other canine viruses were also observed. The complete coding sequence (CDS) of nine Vietnamese and four Thai CaKoV strains were characterized. Phylogenetic analysis revealed a close genetic relationship between Vietnamese and Thai CaKoV strains, which were related to the Chinese strains. CDS analysis indicated a distinct lineage for two Vietnamese CaKoV strains. Selective pressure analysis on the viral capsid (VP1) region showed negative selection, with potential positive selection sites on B-cell epitopes. This study, the first of its kind in Vietnam, provides insights into CaKoV prevalence in dogs of different ages and healthy statuses, updates CaKoV occurrence in Thailand, and sheds light on its molecular characteristics and immune evasion strategies.

Complete genomic sequence analysis and intestinal tissue localization of a porcine Kobuvirus variant in China

Porcine kobuvirus (PKV) infection is very common in both healthy pigs and diarrhea pigs throughout the world. However, there is no proof that it causes diarrhea, and little is known about its role in diarrhea. There are only a few reports concerning porcine kobuvirus separation at present, which makes investigating its invasion and pathogenesis mechanisms difficult. This study sequenced the entire genome of a porcine kobuvirus strain termed "Wuhan2020" after it was isolated from intestinal tissue samples of healthy piglets. The analysis results revealed that it shared the most resemblance with the WUH1 strain (89.5%) and belonged to the same evolutionary branch as the Hungarian strain S-1-SUN. The PKV was located using the in situ hybridization (ISH) approach, which revealed that it was colonized in intestinal villus epithelial cells and lymphocytes in the Peyer's patch. In general, we analyzed the genetic evolution of PKV, discovered PKV susceptible cells and determined PKV localization in the intestine of infected pigs, providing a reference for future research.

Molecular characterization of canine and feline kobuvirus infections in Iran

Kobuviruses are viral pathogens with broad host range presented in human gastroenteritis cases; but, the pathogenesis of these viruses in companion animals is not well described. In the present study, the presence of canine (CaKVs) and feline kobuviruses (FeKVs) was detected in the 100 fecal samples of diarrhoeic and healthy companion dogs and cats by polymerase chain reaction in Tehran, Iran. The prevalence of infection was estimated as 8.00% and 4.00% in dogs and cats, respectively. All positive samples were belonged to non-diarrhoeic animals except for a feline sample being co-infected with panleukopenia. Sequence analysis showed multiple point mutations in canine and feline Iranian strains and new feline strain was detected in the present study. This is the first detection of CaKVs and FeKVs in Iran; but, the exact role of these enteric viral pathogens and their zoonotic risks are better to be clarified in all endemic regions.

Epidemiology and genetic characteristics of murine kobuvirus from faecal samples of Rattus losea, Rattus tanezumi and Rattus norvegicus in southern China

Recently, murine kobuvirus (MuKV), a novel member of the family Picornaviridae, was identified in faecal samples of Rattus norvegicus in China. The limited information on the circulation of MuKV in other murine rodent species prompted us to investigate its prevalence and conduct a genetic characterization of MuKV in Rattus losea, Rattus tanezumi and Rattus norvegicus in China. Between 2015 and 2017, 243 faecal samples of these three murine rodent species from three regions in southern China were screened for the presence of MuKV. The overall prevalence was 23.0% (56/243). Three complete MuKV polyprotein sequences were acquired, and the genome organization was determined. Phylogenetic analyses suggested that our sequences were closely related to Chinese strains and belong to the species Aichivirus A in the genus Kobuvirus. Additional studies are required to understand the true prevalence of MuKV in murine rodent populations in China.

Detection and molecular characterization of kobuvirus from diarrheic goats in Minnesota

Kobuvirus infections are common among humans, rodents, carnivores, pigs, and ruminants. We report herein the complete genome sequence of a novel caprine kobuvirus (MN604700) from diarrheic kids in Minnesota. Whole-genome sequencing revealed a kobuvirus genome of 8,139 nt with a single ORF region encoding a polyprotein of 2,480 amino acids. Further analysis revealed nt substitutions along the genome compared with that of the caprine kobuvirus reference strain, with 93% identity. Phylogenetic analysis indicated that the clade of the caprine kobuvirus was most closely related to porcine kobuviruses rather than bovine or ovine kobuviruses. Using primers designed from this genome, caprine kobuvirus was identified in the stools of other goats. Sanger sequencing of PCR products indicated 3D and VP1 gene nucleotides of this latter strain were 95% and 91% identical with those of MN604700, respectively. There were 35 and 101 nt substitutions in 3D and VP1 genes, respectively. Findings of kobuvirus over a 2-y period may indicate an endemic state, which needs further research. In addition, screening for kobuviruses over large geographic areas is needed to identify the evolutionary connections among different strains.

Epidemiological and phylogenetic analysis of canine kobuviruses in Tangshan, China

Canine kobuviruses (CaKoV) have been found in healthy and diarrheic dogs as well as asymptomatic wild carnivores in various countries. In order to investigate the prevalence and evolution of CaKoV in Tangshan, China, 82 dog fecal samples from pet hospitals in Tangshan were subjected to RT-PCR targeting a segment of the 3D gene of CaKoV. Using this method, we identified CaKoV in 14 samples (17.07%, 14/82). Of the CaKoV-positive samples, 78.57% (11/14) and 50% (7/14) were positive for canine parvovirus and canine coronavirus, respectively. The nucleotide sequences of the 14 strains 96.6%–100% identical to each other and 77.6%–99.2% identical to representative sequences from the NCBI GenBank database. We also amplified the 14 VP1 gene sequences and found that they were 93.3%–99.6% identical to each other and 73.3%–97.8% identical to representative sequences from the NCBI GenBank database. Phylogenetic analysis revealed that the 14 CaKoV strains from Tangshan are closely related to those identified in China and Thailand and display less similarity to those found in Africa, the United States, and Europe. Our data suggest that CaKoV circulated in young pet dogs in Tangshan and displays a high co-infection rate with CCoV and CPV. However, the relationship between the three viruses and their roles in the host requires further investigation.

One-step multiplex TaqMan probe-based method for real-time PCR detection of four canine diarrhea viruses

Viral canine diarrhea has high morbidity and mortality and is prevalent worldwide, resulting in severe economic and spiritual losses to pet owners. However, diarrhea pathogens have similar clinical symptoms and are difficult to diagnose clinically. Thus, fast and accurate diagnostic methods are of great significance for prevention and accurate treatment. In this study, we developed a one-step multiplex TaqMan probe-based real-time PCR for the differential diagnosis of four viruses causing canine diarrhea including, CPV (Canine Parvovirus), CCoV (Canine Coronavirus), CAstV (Canine Astrovirus), and CaKoV (Canine Kobuviruses). The limit of detection was up to 10² copies/μL and performed well with high sensitivity and specificity. This assay was optimized and used to identify possible antagonistic relationships between viruses. From this, artificial pre-experiments were performed for mixed infections, and a total of 82 canine diarrhea field samples were collected from different animal hospitals in Zhejiang, China to assess the method. The virus prevalence was significantly higher than what previously reported based on RT-PCR (Reverse Transcription-Polymerase Chain Reaction). Taken together, these results suggest that the method can be used as a preferred tool for monitoring laboratory epidemics, timely prevention, and effective monitoring of disease progression.

First detection and genetic characterization of canine Kobuvirus in domestic dogs in Thailand

Background

Canine Kobuvirus (CaKoV) has been detected both in healthy and diarrheic dogs and in asymptomatic wild carnivores. In this study, we conducted a survey of CaKoV at small animal hospitals in Bangkok and vicinity of Thailand during September 2016 to September 2018.

Results

Three hundred and seven rectal swab samples were collected from healthy dogs (n = 55) and dogs with gastroenteritis symptoms (n = 252). Of 307 swab samples tested by using one-step RT-PCR specific to 3D gene, we found CaKoV positivity at 17.59% (54/307). CaKoVs could be detected in both sick (19.44%) and healthy (9.09%) animals. In relation to age group, CaKoV could be frequently detected in younger dogs (25.45%). Our result showed no seasonal pattern of CaKoV infection in domestic dogs. In this study, we characterized CaKoVs by whole genome sequencing (n = 4) or 3D and VP1 gene sequencing (n = 8). Genetic and phylogenetic analyses showed that whole genomes of Thai CaKoVs were closely related to Chinese CaKoVs with highest 99.5% amino acid identity suggesting possible origin of CaKoVs in Thailand.

Conclusions

In conclusion, this study was the first to report the detection and genetic characteristics of CaKoVs in domestic dogs in Thailand. CaKoVs could be detected in both sick and healthy dogs. The virus is frequently detected in younger dogs. Thai CaKoVs were genetically closely related and grouped with Chinese CaKoVs. Our result raises the concerns to vet practitioners that diarrhea in dogs due to canine Kobuvirus infection should not be ignored.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1994-6) contains supplementary material, which is available to authorized users.

Detection of canine kobuvirus RNA in diarrheic fecal samples of dogs with parvoviruses

Canine kobuvirus (CaKV) is a member of the Picornaviridae family and the Kobuvirus genus. CaKV was first described in fecal samples from diarrheic dogs in the USA in 2011, with subsequent reports in the UK, Italy, South Korea, China, Tanzania, and Japan. CaKV is frequently identified in feces of animals with or without clinical signs of gastroenteritis. The present study investigated the presence of CaKV in fecal samples from 53 diarrheic dogs from Londrina, southern Brazil. Using a RT-PCR assay, CaKV RNA was identified in three dogs, resulting in an overall occurrence rate of 5.7%. In addition, coinfection with canine parvovirus subtype 2b was detected in all CaKV-positive diarrheic fecal samples. Using a phylogenetic analysis based on the VP1 gene sequence, the Brazilian CaKV field strains were found to be very similar to a previously identified CaKV strain from Brazil that was found in the tissue of a puppy and were also found to be clustered with other CaKV strains detected worldwide and other kobuvirus strains identified in mouse, feline, and human hosts.

New viruses associated with canine gastroenteritis

A number of novel viruses have been associated with canine gastroenteritis in recent years, from viral families as diverse as Caliciviridae and Picornaviridae to Parvoviridae and Circoviridae. The ability of many of these viruses to cause disease is uncertain, but epidemiological studies are continually adding to our knowledge of these potential pathogens. This review presents a summary of the latest research and current understanding of novel viruses associated with canine gastroenteritis.

One-step triplex PCR/RT-PCR to detect canine distemper virus, canine parvovirus and canine kobuvirus

To rapidly distinguish Canine distemper virus (CDV), canine parvovirus (CPV), and canine kobuvirus (CaKoV) in practice, a one-step multiplex PCR/RT-PCR assay was developed, with detection limits of 10^2.1 TCID₅₀ for CDV, 10^1.9 TCID₅₀ for CPV and 10³ copies for CaKoV. This method did not amplify nonspecific DNA or RNA from other canine viruses. Therefore, the assay provides a sensitive tool for the rapid clinical detection and epidemiological surveillance of CDV, CPV and CaKoV in dogs.

First molecular identification of kobuviruses in wolves (Canis lupus) in Italy

Canine kobuviruses (CaKoVs) were first identified in diarrhoeic and asymptomatic dogs in 2011 in the USA. Subsequent studies have demonstrated a worldwide distribution of these viruses, but it is not clear if CaKoVs play a role as enteric pathogens of dogs. More recently, CaKoV RNA has been detected in wild carnivores, including red fox, golden jackal, side-striped jackal and spotted hyena. In this study, we addressed the hypothesis that wolves are susceptible to CaKoV infections. A total of 185 wolf stool samples were collected from necropsied animals and from transects in the Liguria, Piemonte and Valle D'Aosta regions of Italy, and CaKoV RNA was identified in two of these specimens. Both samples were obtained from necropsied wolves, with a prevalence rate of 4.9% (2/41). Sequence analysis of the full-length VP1 region showed that these strains displayed the highest nucleotide (nt) sequence identity (86.3-98.5%) to canine strains identified in the UK and Africa, and to kobuviruses that were previously detected in other African wild carnivores. This suggests that genetically related CaKoV strains circulate in domestic and wild carnivores, with interspecies transmission being not uncommon among carnivores of different ecosystems.

Detection and molecular characterization of porcine kobuvirus in piglets in 2009-2013 in northern Thailand

A total of 636 fecal samples collected from piglets with and without diarrhea during 2009 to 2013 were tested for porcine kobuvirus by RT-PCR. From a total of 528 fecal samples collected from piglets with diarrhea and 108 from healthy controls, 505 (95.6%) and 104 (96.3%) were positive for porcine kobuvirus, respectively. The detection rates of porcine kobuvirus were remarkable equally high in both diarrheic and healthy piglets. Phylogenetic analysis revealed that porcine kobuvirus strains detected in both symptomatic and asymptomatic piglets were genetically closely related to each other and also to other porcine kobuviruses reported worldwide. It was interesting to point out that one of the porcine kobuvirus strains isolated from piglet in our study was similar to a porcine-like bovine kobuvirus reference strain isolated previously in South Korea. This finding provided the evidence to support the interspecies transmission of kobuviruses between cattle and swine.