Duplex SYBR Green I-based real-time PCR assay for the rapid detection of canine kobuvirus and canine astrovirus

First Report on the Molecular Detection of Canine Astrovirus (CaAstV) in Dogs with Gastrointestinal Disease in Ecuador Using a Fast and Sensitive RT-qPCR Assay Based on SYBR Green®

Enteric viruses are responsible for a significant number of gastrointestinal illnesses in dogs globally. One of the main enteric viruses is the canine astrovirus (CaAstV), which causes diarrhea in dogs of various ages. It is linked to symptoms such as diarrhea, vomiting, depression and a significant mortality rate due to gastrointestinal disorders. It is a single-stranded positive RNA virus, with three open reading frames, ORF1a, ORF1b and ORF2, where the last one codes for the virus capsid protein and is the most variable and antigenic region of the virus. The aim of this work is to develop and standardize a quick detection method to enable the diagnosis of this etiological agent in dogs with gastroenteritis in Ecuador in order to provide prompt and suitable treatment. The assay was specific for amplification of the genome of CaAstV, as no amplification was shown for other canine enteric viruses (CPV-2, CCoV and CDV), sensitive by being able to detect up to one copy of viral genetic material, and repeatable with inter- and intra-assay coefficients of variation of less than 10% between assays. The standard curve showed an efficiency of 103.9%. For the validation of this method, 221 fecal samples from dogs affected with gastroenteritis of various ages from different provinces of Ecuador were used. From the RT-qPCR protocol, 119 samples were found positive for CaAstV, equivalent to 53.8% of the samples processed. CaAstV was detected in dogs where both the highest virus prevalence in the tested strains and the highest viral loads were seen in the younger canine groups up to 48 weeks; in addition, different strains of the virus were identified based on a sequenced fragment of ORF1b, demonstrating the first report of the presence of CaAstV circulating in the domestic canine population affected by gastroenteritis in Ecuador, which could be associated with the etiology and severity of enteric disease.

The Significance and Importance of dPCR, qPCR, and SYBR Green PCR Kit in the Detection of Numerous Diseases

Digital PCR (dPCR) is the latest technique that has become commercially accessible for various types of research. This method uses Taq polymerase in a standard polymerase chain reaction (PCR) to amplify a target DNA fragment from a complex sample, like quantitative PCR (qPCR) and droplet digital PCR (dd- PCR). ddPCR may facilitate microRNA (miRNA) measurement, particularly in liquid biopsy, because it has been proven to be more effective and sensitive, and in this method, ddPCR can provide an unprecedented chance for deoxyribonucleic acid (DNA) methylation research because of its capability to increase sensitivity and precision over conventional PCR-based methods. qPCR has also been found to be a valuable standard technique to measure both copy DNA (cDNA) and genomic DNA (gDNA) levels, although the finding data can be significantly variable and non-reproducible without relevant validation and verification of both primers and samples. The SYBR green quantitative real-time PCR (qPCR) method has been reported as an appropriate technique for quantitative detection and species discrimination, and has been applied profitably in different experiments to determine, quantify, and discriminate species. Although both TaqMan qRT-PCR and SYBR green qRT-PCR are sensitive and rapid, the SYBR green qRT-PCR assay is easy and the TaqMan qRT-PCR assay is specific but expensive due to the probe required. This review aimed to introduce dPCR, qPCR, SYBR green PCR kit, and digital PCR, compare them, and also introduce their advantages in the detection of different diseases.

A One-Year Retrospective Analysis of Viral and Parasitological Agents in Wildlife Animals Admitted to a First Aid Hospital

This study aimed to provide information on the presence and frequency of viral and parasitic agents in wildlife presented to a Veterinary Teaching Hospital in 2020-2021. Serum and faecal samples were collected from 50 rescued animals (roe deer, fallow deer, foxes, badgers, pine martens, and porcupines) and examined by serological, molecular, and parasitological techniques. Transtracheal wash (TTW) was also collected post-mortem from roe deer. Overall, the results of the different techniques showed infections with the following viral and parasitic agents: Bovine Viral Diarrhea Virus, Small Ruminant Lentiviruses, Kobuvirus, Astrovirus, Canine Adenovirus 1, Bopivirus, gastrointestinal strongyles, Capillaria, Ancylostomatidae, Toxocara canis, Trichuris vulpis, Hymenolepis, Strongyloides, Eimeria, Isospora, Dictyocaulus, Angiostrongylus vasorum, Crenosoma, Dirofilaria immitis, Neospora caninum, Giardia duodenalis, and Cryptosporidium. Sequencing (Tpi locus) identified G. duodenalis sub-assemblages AI and BIV in one roe deer and one porcupine, respectively. Adult lungworms collected from the TTW were identified as Dictyocaulus capreolus (COX1 gene). This is the first molecular identification of G. duodenalis sub-assemblage AI and D. capreolus in roe deer in Italy. These results show a wide presence of pathogens in wild populations and provide an overview of environmental health surveillance.

First report of canine Astrovirus and Sapovirus in Greece, hosting both asymptomatic and gastroenteritis symptomatic dogs

Background

Astrovirus, Norovirus and Sapovirus are widely distributed viruses in humans and animals worldwide. They have frequently been associated with disease, mainly of gastroenteric nature. In dogs, these viruses have been detected both in symptomatic and asymptomatic animals, mainly of young age.

Methods

In the present epidemiologic study, we investigated the presence of canine Astrovirus (CAstV), canine Norovirus (canine NoV) and canine Sapovirus (Canine SaV) in saliva and stools of 201 domestic dogs originating from throughout Greece, based on two different molecular methods, i.e. conventional and SYBR-Green Real-time RT-PCR. The samples derived from young and adult asymptomatic and symptomatic animals. CAstV was detected in 15/201 (7.5%) and 29/201 (15%) of the examined dogs using conventional RT-PCR and SYBR-Green Real time RT-PCR, respectively.

Results

The prevalence of the virus was higher at healthy dogs, with a slight discrepancy of the two methods on the aspect of age (67% young dogs with the method of conventional RT-PCR, versus 52% adult positive dogs with the method of SYBR-Green Real-time RT-PCR). Canine SaV was detected in 52/201 (23%) of the dogs (mainly young and asymptomatic), with the method of SYBR-Green Real-time RT-PCR only, while canine NoV was not detected in any sample with either of the two methods applied. Sequencing of the CAstV positive samples resulted in the acquisition of one CAstV sequence. Phylogenetic analysis confirmed the results, clustering the CAstV sequence with homologous canine hosting sequences from other countries.

Conclusions

CAstV and Canine SaV were proved to circulate in Greek dogs. SYBR-Green Real time RT-PCR showed greater sensitivity in the detection of these viruses. Additionally, we were able to specify the CAstV strain that circulates in Greece, through phylogenetic analysis. To our knowledge, this is the first epidemiological study of CAstV and canine SaV in dogs in Greece, as well as the first time detected in dogs from Greece.

Establishment of duplex SYBR Green I-based real-time PCR assay for simultaneous detection of duck hepatitis a virus-1 and duck astrovirus-3

Duck viral hepatitis (DVH) mainly affects ducklings under 1 month of age, causes liver necrosis, enlargement, and hemorrhage, and is highly lethal, seriously jeopardizing the duck industry. The prevalence of serotypes DHAV-1 and DAstV-3 is increasing, and co-infection is common. Moreover, the similar clinical characteristics of the DHAV-1 and DAstV-3 infections and high frequency of co-infection make diagnosis difficult. In this study, to establish a method for the rapid simultaneous detection of DHAV-1 and DAstV-3 , two pairs of specific primers were designed according to their conserved gene regions. A SYBR Green I-based real-time PCR assay was successfully established that can quickly and differentially detect the two viruses. Moreover, the assay is highly specific and does not show cross-reaction with other common viruses. The detection limit of the method is 7.34 × 10 1 copies/μL and 3.78 × 10 1 copies/μL for DHAV-1 and DAstV-3, respectively, indicating high sensitivity. A total of 34 clinical samples were tested using the established method; the positive rates for DHAV-1 and DAstV-3 was 14.71% and 8.82%, respectively, and that for co-infection was 2.94% (1/34), which was better than that obtained with conventional PCR. In summary, the SYBR Green I-based real-time PCR assay established in this study has high specificity, good sensitivity and accuracy, high feasibility, and is rapid. Thus, it can be a powerful tool for the co-infection detection of DHAV-1 and DAstV-3 and for future epidemiological studies.