Many viruses are involved in concomitant infections, which are prevalent in nature. In mixed infections, one or both infectious agents may be increased, reduced, or both may be increased while the other is suppressed. Canine distemper virus (CDV) and Canine parvovirus- 2 (CPV-2) are important causes of gastroenteritis in dogs. Detection of these viruses is challenging since the symptoms are very similar. CDV is a member of the morbillivirus genus in the Paramyxoviridae family, and CPV-2 is a member of the Protoparvovirus genus in the Parvoviridae family; and both predominantly affect puppies and induce gastrointestinal symptoms in dogs. The purpose of this study was to contribute to the differential diagnosis of dogs with gastrointestinal symptoms. A PCR technique with specific primers was used to identify CDV and CPV-2 infections in gastroenteric dogs, and clinical changes in the infected dogs were monitored. The VP2 structural gene of CPV and the nucleocapsid gene of CDV were partially amplified in the study. PCR amplified the partial fragments of the CDV nucleocapsid (287 bp) and CPV-2 VP2 proteins (583 bp) from feces. In total, 3 out of 36 stool samples were positive for CDV and CPV-2 in the same dogs. Gasterointestinal symptoms also supported the diagnosis of concomitant infection with CDV and CPV-2 in these dogs. Dehydration and diarrhea in dogs can be signs of various diseases, such as viral, bacterial, and parasitic infections. After the elimination of non-viral pathogens, CDV and CPV-2 should also be simultaneously investigated to establish what is causing these symptoms. This study demonstrates the potential utility of correct diagnosis for the control of viral infection in dogs, but more research with a broader use of PCR-based detections is needed to assess its impact on differential diagnosis for concomitant infections.

Canine distemper virus (CDV) infects wild and domestic Canidae worldwide. The hemag- glutinin (H) gene has the highest genetic variation in the genome of this virus. Thus, the H gene is commonly used for lineage identification and genetic analyses. In order to study the genetic characteristics and pathogenicity of CDV strains prevalent in China, 132 samples were collected from domestic dogs with suspected CDV infection, 58 samples were confirmed to be positive, and the H gene was successfully amplified from 15 samples. The epidemic strain was identified as type Asia-1 and the novel mutations, A51T, V58I, R179K and D262N, were detected in this strain. Isolated strains, BJ16B53, BJ16B14, and BJ17B8, were used for an animal infection experiment in raccoon dogs. BJ16B53 and BJ16B14 were found to cause clinical symptoms, death, and exten- sive lesions in various organs. These results are expected to facilitate the development of effective strategies to monitor and control CDV infection in China.

In order to understand infection of avian influenza A virus (AIV) and canine distemper virus (CDV) in the Siberian Tiger in Northeast China, 75 Siberian Tiger serum samples from three cap- tive facilities in northeastern China were collected. AIV and CDV antibody surveillance was test- ed by using hemagglutination inhibition and serum neutralization methods. The results showed that the seroprevalence of H5 AIV, H9 AIV and CDV was respectively 9.33% (7/75), 61.33% (46/75) and 16% (12/75). In the 1<years <2 and > 5 year-old group, the seroprevalence of the H9 AIV was 24% and 80% (P < 0.01), and the CDV seroprevalence was 6% and 36% (P < 0.01), respectively. It was demonstrated that 3 (4%) out of 75 serum samples were AIV+CDV seropos- itive, with 2.67% (2/75) in H9+AIV and 1.33% (1/75) in H5+H9+AIV. To our knowledge, this is the first report of AIV and CDV seroprevalence in Siberian Tigers in China, which will provide base-line data for the control of AIV and CDV infection in Siberian Tigers in China.