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.