The preservation of rare species of mammals, as a rule, hinges on the preservation of their habitat and food supply, and on reducing the human impact. The spread of infectious diseases poses yet another serious threat for the stable survival of a rare species of mammal, especially if its population is very low.    A decrease in population and heightened risk of inbreeding are accompanied by a rise in homozygous animals, which leads to reduced immune response and increased susceptibility to various diseases. Thus, the identification of potential infectious diseases posing a threat to the survival of a species, as well as projects for the reintroduction of rare species, have become a priority in the implementation of environmental projects.

This study is aimed at identifying the spread of infectious diseases in the populations of the Amur tiger (Panthera tigris altaica) and its potential prey in the Russian Far East, primarily in the Ussuri Nature Reserve. The research was carried out in 2008-2010 as part of a programme to study the population of the Amur tiger in the Russian Far East, and included the collection of blood and faeces samples from all captured animals. Scientists analysed the occurrence of antibodies (and more rarely, antigens) to the following diseases: distemper, parvovirus enteritis (panleukopenia), toxoplasmosis, herpes virus, influenza A virus, chlamydia, mycoplasmosis, coronavirus enteritis, feline immunodeficiency virus and feline leukaemia virus. The collected material included blood samples from 11 tigers (trapped in a wild), as well as a lynx, a Far Eastern forest cat, five brown and two Himalayan bears, two Amur badgers and one raccoon dog.

No individual tigers seropositive to the following diseases were found: chlamydia, mycoplasmosis, immunodeficiency and coronavirus enteritis, leukaemia and parvovirus enteritis. Antibodies to the herpes virus were found in one of the tigers (11.1%). Toxoplasmosis was found to be the most common disease, as it was diagnosed in five tigers (45.5%) and a lynx. Three tigers (27.3%) were seropositive for canine distemper virus, and two among them died within a month after the samples were taken.

Widespread instances of canine distemper virus, primarily in domestic and feral dogs, and its identification in other species of carnivorous mammals (one of the bears) in combination with a high mortality rate, make it one of the most dangerous diseases for the survival of tigers in the Far East of Russia.

However, other diseases (herpes – 70 % , toxoplasmosis – 40% , mycoplasmosis – 30%) that are widespread among the potential prey of the tiger, may affect the animal welfare of the Amur tiger, including indirect one, through the regulation  in the numbers of its main prey.