Detection of a group 2 coronavirus in dogs with canine infectious respiratory disease

Abstract

An investigation into the causes of canine infectious respiratory disease was carried out in a large rehoming kennel. Tissue samples taken from the respiratory tract of diseased dogs were tested for the presence of coronaviruses using RT-PCR with conserved primers for the polymerase gene. Sequence analysis of four positive samples showed the presence of a coronavirus with high similarity to both bovine and human coronavirus (strain OC43) in their polymerase and spike genes, whereas there was a low similarity to comparable genes in the enteric canine coronavirus. This canine respiratory coronavirus (CRCV) was detected by RT-PCR in 32/119 tracheal and 20/119 lung samples, with the highest prevalence being detected in dogs with mild clinical symptoms. Serological analysis showed that the presence of antibodies against CRCV on the day of entry into the kennel decreased the risk of developing respiratory disease.

Fig. 1

Consensus tree for cDNA sequences from a 251-nucleotide region of the polymerase gene of 12 coronaviruses. The sequence obtained from the canine respiratory coronavirus is designated T101. The numbers indicate bootstrap values obtained by analysis of 100 data sets. BCV, bovine coronavirus; CCV, canine coronavirus; FIPV, feline infectious peritonitis virus; HEV, hemagglutinating encephalomyelitis virus; IBV, infectious bronchitis virus; MHV, mouse hepatitis virus; OC43, human coronavirus strain OC43; SDAV, sialodacryoadenitis virus; TCV, turkey coronavirus; TGEV, transmissible gastroenteritis virus; 229E, human coronavirus strain 229E; T101, canine respiratory coronavirus (PCR product from tracheal sample T101).

Fig. 2

RT–PCR using consensus primers directed to the hemagglutinin/esterase gene of bovine and human coronavirus (strain OC43). The agarose gel electrophoresis shows PCR products of the expected size of 497 bp for the positive control (BCV) and four tracheal samples (T90–T105). BCV, bovine coronavirus positive control sample; A72, coronavirus-negative A72 cells; H₂O, PCR mix without DNA; T90–T105, tracheal samples of study dogs; 1 kb, molecular size standard (Promega).

Fig. 3

Comparison of the prevalence of respiratory disease in two groups of dogs: Dogs in group 1 were positive for serum antibodies to respiratory coronavirus on the day of entry into the kennel; dogs in group 2 were negative. The graph shows the percentage of dogs developing respiratory disease in group 1 compared to group 2 (P < 0.001). N is the total number of dogs in each group.