Longitudinal study of viruses associated with canine infectious respiratory disease

Abstract

In this investigation a population of dogs at a rehoming center was monitored over a period of 2 years. Despite regular vaccination of incoming dogs against distemper, canine adenovirus type 2 (CAV-2), and canine parainfluenza virus (CPIV), respiratory disease was endemic. Tissue samples from the respiratory tract as well as paired serum samples were collected for analysis. The development of PCR assays for the detection of CPIV, canine adenovirus types 1 and 2, and canine herpesvirus (CHV) is described. Surprisingly, canine adenovirus was not detected in samples from this population, whereas 19.4% of tracheal and 10.4% of lung samples were positive for CPIV and 12.8% of tracheal and 9.6% of lung samples were positive for CHV. As reported previously, a novel canine respiratory coronavirus (CRCoV) was detected in this population (K. Erles, C. Toomey, H. W. Brooks, and J. Brownlie, Virology 310:216-223, 2003). Infections with CRCoV occurred mostly during the first week of a dog's stay at the kennel, whereas CPIV and CHV were detected at later time points. Furthermore, the evaluation of an enzyme-linked immunosorbent assay for detection of antibodies to CPIV and an immunofluorescence assay for detection of antibodies to CHV is described. This study shows that CPIV is present at kennels despite vaccination. In addition, other agents such as CHV and CRCoV may play a role in the pathogenesis of canine respiratory disease, whereas CAV-2 and canine distemper virus were not present in this population, indicating that their prevalence in the United Kingdom is low due to widespread vaccination of dogs.

FIG. 1.

PCR for detection of canine herpesvirus (top) and nested RT-PCR for detection of canine parainfluenza virus (bottom). Lanes 1, molecular size marker (Sigma); lanes 2, positive control (DNA extracted from MDCK cells infected with canine herpesvirus or cDNA from MDCK cells infected with CPIV, respectively); lanes 3, DNA or cDNA sample obtained from uninfected MDCK cells; lanes 4, DNA or cDNA samples from lung tissues of dogs suffering from respiratory disease. Lanes 2 and 4 show a PCR band of the expected size of 494 bp for CHV or 182 bp for CPIV.

FIG. 2.

Prevalences of viruses at different time points as determined by PCR on tracheal samples. The x axis represents the number of days the dogs had stayed at the kennel before sampling. Each bar represents the percentage of dogs that were positive for the respective virus. The line represents the percentage of dogs that showed signs of respiratory disease. The total number of dogs tested at each time point was as follows: 1 to 7 days, n = 16; 8 to 14 days, n = 78; 15 to 21 days, n = 22; 22 to 28 days, n = 17; 29 days or more, n = 16.