Whataroa virus four decades on: Emerging, persisting, or fading out?

Abstract

Whataroa virus, first detected in 1962 in bird populations around Whataroa township, is the only mosquito-borne virus circulating in New Zealand that has been isolated. Even though at least one other mosquito-borne pathogen (avian malaria) has greatly increased in prevalence in New Zealand in recent decades, no surveillance for Whataroa virus in its vertebrate hosts has been carried out for four decades. This is of concern since Whataroa virus may infect humans, possibly causing influenza-like symptoms. Here we reassess the status of Whataroa virus in the same bird species in the same area where it was detected previously. Molecular diagnostics identified Whataroa virus in three out of 95 non-native birds screened: two out of eight song thrushes Turdus philomelos, and one out of nine blackbirds Turdus merula. The detection of virus in birds, in contrast with recent screening of mosquitoes, highlights how wildlife surveillance for pathogens can be far more effective than vector surveillance. Results of this survey indicate the virus has not increased substantially in prevalence since last monitored, possibly because of little change in the local mosquito vector community. Finally, virus detection in the two Turdus species alone supports earlier claims that these non-native hosts act as reservoirs that maintain the virus, sourcing spillover infections in other native and non-native species. A similar role for the blackbird in avian malaria epidemiology in New Zealand has also recently been hypothesized. © 2010 The Royal Society of New Zealand.