Canine distemper virus infection among wildlife before and after the epidemic.

In 2007-2008, a canine distemper virus (CDV) epidemic occurred among wild animals in Wakayama Prefecture, Japan, and many mammals, including the wild boar and deer, were infected. In this study, CDV prevalence among wild animals was surveyed before and after the epidemic. At first, an enzyme-linked immunosorbent assay (ELISA) with horseradish peroxidase-conjugated protein A/G was established to detect CDV antibodies in many mammalian species. This established ELISA was available for testing dogs, raccoons and raccoon dogs as well as virus-neutralization test. Next, a serological survey of wild mammalians was conducted, and it was indicated that many wild mammalians, particularly raccoons, were infected with CDV during the epidemic, but few were infected before and after the epidemic. On the other hand, many raccoon dogs died during the epidemic, but CDV remained prevalent in the remaining population, and a small epidemic occurred in raccoon dogs in 2012-2013. These results indicated that the epidemic of 2007-2008 may have been intensified by transmission to raccoons.

Epizootic canine distemper virus infection among wild mammals.

In the spring of 2007, seven raccoon dogs and a weasel were captured near the city of Tanabe in Wakayama prefecture, Japan. The causative agent of the animals' death 1-2 days after capture was identified as canine distemper virus (CDV) by virus isolation, immunostaining with an anti-CDV polyclonal antibody, and a commercially available CDV antigen-detection kit. Sequence analysis of hemagglutinin genes indicated the isolated viruses belong to genotype Asia-1 and possess the substitution from tyrosine (Y) to histidine (H) at position 549 that is associated with the spread of CDV to non-canine hosts. A serosurvey for CDV was then conducted among wild animals in the region. The animals assayed consisted of 104 raccoons, 41 wild boars, 19 raccoon dogs, five Sika deer, two badgers, one weasel, one marten, one Siberian weasel and one fox. Virus-neutralization (VN) tests showed that, except for fox and weasel, all of the species assayed had VN antibodies to CDV. Interestingly, 11 of the 41 wild boars (27%) and two of the five Sika deer assayed possessed VN antibodies to CDV. These findings indicate that CDV infection was widespread among wild mammals during this epizootic.

Detection of antibody to canine distemper virus in wild raccoons (Procyon lotor) in Japan.

Canine distemper virus (CDV) causes a lethal disease among members of the Carnivora. To clarify the distribution of CDV in wild animals, we examined 106 raccoon sera collected from two prefectures in Japan, Hyogo and Osaka, from 2005 to 2007. Among them, 34 raccoons (32.1%) possessed a virus-neutralizing (VN) antibody to KDK-1 strain (genotype Asia-1). There was no significant difference in seroprevalence of CDV regardless of places, gender, and body weights. In Hyogo, a geometric mean of VN titers to KDK-1 was significantly higher than that to Onderstepoort (vaccine strain), indicating that KDK-1-like CDV different from vaccine strain might have spread among raccoon population in Hyogo. In conclusion, CDV is epidemic among feral raccoons in Japan, suggesting that CDV might have been spreading among Japanese wild animals.

Establishment of canine and feline cells expressing canine signaling lymphocyte activation molecule for canine distemper virus study.

Signaling lymphocyte activation molecule (SLAM) is one of the receptors for canine distemper virus (CDV). In this study, canine and feline cells expressing canine SLAM, designated A-72/cSLAM and CRFK/cSLAM, were established for the in vitro study of canine distemper. Recent CDV isolates, KDK-1 and 246, which belong to genotypes Asia/H1 and Asia/H2, respectively, rapidly grew and produced distinct syncytia in both the SLAM-expressing cells. The virus-neutralizing (VN) test was successfully performed using these cells, and the results indicated that sera from dogs experimentally infected with KDK-1 had higher VN titers for homologous strain KDK-1 than for heterologous strain 246 and the vaccine Onderstepoort. These newly established cells expressing canine SLAM would help virological and serological analyses of canine distemper.