The chytrid fungus () is notorious amongst current conservation biology challenges, responsible for mass mortality and extinction of amphibian species. World trade in amphibians is implicated in global dissemination. Exports of South African have led to establishment of this invasive species on four continents. naturally infects this host in Africa and now occurs in several introduced populations. However, no previous studies have investigated transfer of infection into co-occurring native amphibian faunas. A survey of 27 U.K. institutions maintaining . for research showed that most laboratories have low-level infection, a risk for native species if animals are released into the wild. RT-PCR assays showed in two introduced U.K. populations of . , in Wales and Lincolnshire. Laboratory and field studies demonstrated that infection levels increase with stress, especially low temperature. In the U.K., native amphibians may be exposed to intense transmission in spring when they enter ponds to spawn alongside . that have cold-elevated infections. Exposure to cross-infection has probably been recurrent since the introduction of . , >20 years in Lincolnshire and 50 years in Wales. These sites provide an important test for assessing the impact of . on spread. However, RT-PCR assays on 174 native amphibians (, , and spp.), sympatric with the -infected introduced populations, showed no foci of self-sustaining transmission associated with . . The abundance of these native amphibians suggested no significant negative population-level effect after the decades of co-occurrence.