The endangered population of Amur tigers (Panthera tigris altaica) in the Russian Far East (RFE) faces an increasing risk of extinction due to infection with canine distemper virus (CDV). Short-lasting CDV infections are unlikely to be maintained in small populations of species with limited connectivity like tigers, where viruses fade out as susceptible hosts are depleted. Multi-host pathogens can persist in more abundant host species that can act as reservoirs of infection for threatened populations. This study combines assessments of host demography, serology and viral phylogeny to establish the relative contribution of domestic dogs and small bodied wild mesocarnivores to the maintenance of CDV, and as sources of infection for tigers. No antibodies were detected among tigers sampled prior to 2000 (n=19), but were measured in 35.7% of tigers in subsequent years (n=56), with at least five discrete transmission events occurring in one well-monitored population. Viral sequences from three tigers and one Far Eastern leopard (P. pardus orientalis) aligned within the Arctic-like clade of CDV, and shared recent common ancestry with viruses from 22 other wild carnivores from the region. Extensive spatial mixing of wild carnivore lineages suggested long chains of transmission consistent with a maintenance population. The exposure of tigers following 2000 coincides with increases in sable (Martes zibellina) numbers and hunting pressure, which could lead to greater pathogen prevalence and potential for spill over from a wild reservoir. The ratio of humans to dogs in rural areas in the RFE are among the lowest in the world (1.73), but the overall number of dogs has been stable during the period of increased CDV exposure in tigers. The only CDV sequence obtained from dogs shared high identity with Asia-4 clade viruses from dogs in Thailand, and was distantly related to wildlife sequences from the RFE. Serum antibodies were detected in dogs in all 26 communities where households were surveyed, but seroprevalence was higher in remote, less densely populated areas, suggesting possible transmission from wildlife. Although the maintenance of CDV in Russian dogs remains unconfirmed, the strong support for a wildlife reservoir limits options for managing the impact of CDV on tiger populations. The high turnover of large and often inaccessible populations of mesocarnivores combines with limitations in vaccine safety, efficacy and delivery, to render the control of CDV in a wildlife reservoir untenable. Managing the impact of CDV on Amur tigers must therefore focus on restoring the size and integrity of remaining tiger populations to withstand future outbreaks. The safety and efficacy of vaccine products for tigers should also be investigated, for use in low coverage vaccination strategies that could enhance the long-term persistence of tiger populations.