Invasive, non-native species are a major threat to global biodiversity. Stoats were introduced from Britain to New Zealand in the 1880s and have since caused grave conservation problems. A histopathological and serological survey of disease and infection in stoats from New Zealand was undertaken to identify agents that might be used or modified to control this population. Of 60 stoats examined, 63% exhibited inflammation of the lung, mostly occurring as local or diffuse interstitial pneumonia, 30% showed signs of inflammatory liver disease and 14% were positive for antibodies reactive with feline calicivirus. In Britain only 11% of 44 stoats exhibited symptoms of pulmonary inflammatory disease, suggesting higher rates of infection or compromise of the pulmonary immune system among invasive stoats, possibly related to genetic founder effects or environmental variation. These findings could be exploited in biological control programmes. (c) 2007 Elsevier Ltd. All rights reserved.