Native and invasive bird interactions increase the spread of Newcastle disease in urban environments

Due to their large population sizes, synanthropic birds, including native and invasive species, can transmit pathogens to other vertebrates, and even humans. In particular, Newcastle disease virus (NDV) can cause lethal infections in a wide range of avian species as well as mild infections in humans and other non-avian hosts. In this study conducted in Barcelona, Spain, we assessed the seroprevalence of NDV in three synanthropic species comprising one native species (feral pigeon, Columba livia var. domestica; N = 16) and two invasive parrots (monk parakeet, Myiopsitta monachus, N = 50; and rose-ringed parakeet, Psittacula krameri, N = 23). These species are considered to have played important roles in the introduction and spread of NDV due to their high population densities, gregariousness, and prolonged viral shedding through faeces. We found a high seroprevalence of NDV in the feral pigeon (56