Introduction

Emerging canine respiratory coronavirus (CRCoV) causes mild to severe respiratory disease in dogs worldwide. The genetic analysis reveals that CRCoV is similar to human (HCoV) and bovine coronavirus (BoV) and posed ability to interspecies transmission. In Thailand, the genetic information of CRCoV is limited.

Objectives

This study aimed to characterize CRCoVs in dogs in Thailand during January 2016 - December 2017.

Methods

From January 2016 to December 2017, 375 nasal swab samples were collected from dogs with respiratory signs. The samples were examined for CRCoV by using RT-PCR assay. Selected RNA samples were subjected to spike (S) gene sequencing based on age, breed, severity of clinical signs, collection date, and location.

Results

In this study, occurrence of CRCoV was 8.8% (33/375). Five Thai CRCoVs were selected for S gene sequencing. Our results show that nucleotide identities of Thai CRCoVs (THA1-CRCoV) and CRCoV-BJ232, HCoV-OC43, and BoV-Quebec were 99.8%, 97.1%, and 97%, respectively (Table 1). Phylogenetic analysis showed that all Thai CRCoVs belong to canine Asian lineage of betacoronavirus (subgroup A coronavirus) which were grouped in the same cluster with human coronaviruses and bovine coronaviruses (Figure 1).

Table 1. Nucleotide similarities of spike gene of THA1-CRCoV to other CoVs from GenBank database

Figure 1 Phylogenetic analysis of spike gene of coronaviruses (betacoronavirus genus). The circle symbols present Thai CRCoVs in this study.

Conclusions

CRCoV is circulating in dogs in Thailand and Thai CRCoVs were closely related to CRCoV Asian strains, HCoVs, and BCoVs. Furthermore, whole genome sequencing is in process for better understanding of the viral diversity and evolution.