Abstract
Lethal infections with canine distemper virus (CDV) have recently been diagnosed in Amur tigers (Panthera tigris altaica), but long-term implications for the population are unknown. This study evaluates the potential impact of CDV on a key tiger population in Sikhote-Alin Biosphere Zapovednik (SABZ), and assesses how CDV might influence the extinction potential of other tiger populations of varying sizes. An individual-based stochastic, SIRD (susceptible-infected-recovered/dead) model was used to simulate infection through predation of infected domestic dogs, and/or wild carnivores, and direct tiger-to-tiger transmission. CDV prevalence and effective contact based on published and observed data was used to define plausible low- and high-risk infection scenarios. CDV infection increased the 50-year extinction probability of tigers in SABZ by 6.3% to 55.8% compared to a control population, depending on risk scenario. The most significant factors influencing model outcome were virus prevalence in the reservoir population(s) and its effective contact rate with tigers. Adjustment of the mortality rate had a proportional impact, while inclusion of epizootic infection waves had negligible additional impact. Small populations were found to be disproportionately vulnerable to extinction through CDV infection. The 50-year extinction risk in populations consisting of 25 individuals was 1.65 times greater when CDV was present than that of control populations. The effects of density dependence do not protect an endangered population from the impacts of a multi-host pathogen, such as CDV, where they coexist with an abundant reservoir presenting a persistent threat. Awareness of CDV is a critical component of a successful tiger conservation management policy.
Highlights
Worldwide tiger populations are at an all-time low, with estimated numbers of breeding females reduced to approximately 1,000 animals [1]
Serological findings suggest that canine distemper virus (CDV) may be an emerging threat to Amur tigers (Panthera tigris altaica) in the Russian Far East [5], with clinical cases in 2003 [6,7] and 2010 [7]
An individual-based stochastic SIRD model was used to simulate the impact of introducing CDV to the Amur tiger population in Sikhote-Alin Biosphere Zapovednik (SABZ)
Summary
Worldwide tiger populations are at an all-time low, with estimated numbers of breeding females reduced to approximately 1,000 animals [1]. Remaining populations are mostly small and fragmented, vulnerable to stochastic events that reduce survival of breeding adults [2]. Serological findings suggest that canine distemper virus (CDV) may be an emerging threat to Amur tigers (Panthera tigris altaica) in the Russian Far East [5], with clinical cases in 2003 [6,7] and 2010 [7]. Several cases have been reported in wild tigers in India [8]. The implications of this threat to tiger population dynamics remain unknown
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