Understanding the dynamics of canine distemper virus in Amur tigers and Far Eastern leopards in the Russian Far East

Canine distemper virus (CDV) has recently been identified as a threat to Amur tigers (Panthera tigris altaica) and Far Eastern leopards (P. pardus orientalis) in the Russian Far East. This study aimed to describe the... [ view full abstract ]

Canine distemper virus (CDV) has recently been identified as a threat to Amur tigers (Panthera tigris altaica) and Far Eastern leopards (P. pardus orientalis) in the Russian Far East. This study aimed to describe the epidemiology of CDV in the Russian Far East and to inform the design of control strategies to reduce infection of tigers and leopards. Archived and novel samples were collected from domestic dogs, wild mesocarnivores and large carnivores from three study areas with varying human densities. CDV-specific primers were used to amplify whole haemagglutinin and fusion genes for sequencing. Viral neutralization titers were measured using the Onderstepoort derived Bussell strain, and multivariate models used to identify risk factors for CDV exposure. Between 1993 and 1999 CDV neutralizing antibodies were detected in 7.5% (n=40, CI:2.6–19.9%) of large carnivore samples, confirming the presence of the virus during this period. Between 2000 and 2011 seroprevalence was 21.1% (n=71, CI:13.2–32.0%) suggesting that transmission may have increased. CDV sequences were amplified from six tigers in 2003, 2006, 2010, and 2013, a grey wolf (Canis lupus) in 2013, and a leopard in 2015, which aligned within the Arctic-like clade of CDV. These viruses aligned closely to 20 sequences obtained from wild mesocarnivores collected between 2012 and 2014. No virus was detected from 73 sick and 633 healthy dogs sampled. Neutralizing antibodies were measured in mesocarnivores (24.7%, n=101, CI:17.4-34.0%), and unvaccinated dogs (27.2%, n= 464, CI:23.3–31.4%). Study area and age were found to be significant predictors of exposure in dogs, with significantly higher seroprevalence in the lowest density rural study area (OR 9.6, CI:2.8-44.8%). These findings confirm that CDV is circulating over a wide area among domestic and wild carnivores in the RFE. The prominent role of wild carnivores in CDV circulation limits options for mitigation via targeted vaccination of large felids.