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%) and monk parakeet (38%) but a low seroprevalence in the rose-ringed parakeet (4%). These differences may be explained by the frequent interactions among feral pigeons and monk parakeets in their daily lives facilitating viral transmission from the former to the latter, because the feral pigeon is a well-known NDV reservoir. By contrast, the low seroprevalence of NDV in rose-ringed parakeets could be explained by its less frequent contacts with other urban bird species. The high seroprevalence of NDV in feral pigeons and monk parakeets provides new insights into the roles of novel interspecific relationships in the transmission and spread of NDV, and the risk of these synanthropic species as a source of NDV in urban environments. Finally, our findings highlight the need to monitor NDV in both native and non-native birds to prevent its spread to poultry, wildlife, and humans.