Dead bird surveillance

In a current project funded by the FWF (Austrian Science Fund) we investigate whether infections with different avian blood parasites (Plasmodium, Haemoproteus, Leucocytozoon) are more frequently responsible for severe diseases and mortalities in different orders of native wild birds than initially thought. The accessible samples are biased because the majority of them originates from birds that (1) were sampled during epidemics of lethal Usutu virus infection, (2) had been submitted to an avian clinic for potential treatment and (3) were mist net captured during ringing campaigns. In this collection (consisting of approximately 1000 individuals) certain bird families, among them Motacillidae, Alaudidae, Picidae, Paridae, Passeridae, Emberizidae and Fringillidae, are grossly underrepresented. In order to partially resolve this bias we propose a citizen science approach for reporting and collecting particularly bird carcasses of the above mentioned families for assessment of haemosporidian infections. We believe that participation of citizens (crowdsourcing) in reporting, identification and submission of carcasses of dead birds is a powerful tool to generate sufficient numbers of required bird species for avian haemosporidian research. The goal of this project is to get access to bodies of dead birds for scientific work-up. The potentially high number of people with interest in bird watching and nature conservation will be encouraged by press releases, web- and social media-based information and in close cooperation with the Austrian bird conservation society BirdLife to report dead birds and to submit carcasses to our laboratory. Citizen science has been successfully applied in surveillance projects for different viral, bacterial and protozoal infections of wild birds. In the context of avian haemosporidioses/avian malaria this approach has not been featured so far, although we consider it a powerful tool for making a high number of bird carcasses available for scientific research. The project will be coordinated and supervised by researchers from the Institute of Pathology at the University of Veterinary Medicine Vienna. They have gained experience with comparable citizen science projects resulting in collection and submission of large numbers of Turdidae (especially blackbirds) during Usutu virus surveillance.

Monitoring of lethal avian haemosporidian infections by dead bird surveillance Avian haemosporidioses are common in birds and their manifestations can range from subclinical infections to severe disease, depending on the involved parasite and bird species. Clinical haemosporidioses are mostly observed in non-adapted zoo or aviary birds, whereas in wild birds, particularly passerines, haemosporidian infections frequently seem to be asymptomatic. However, a recent study from Austria, investigating a large number of deceased Eurasian blackbirds showed pathogenic haemosporidian infections due to high parasite burdens of Plasmodium matutinum LINN1, a common parasite in this bird species, suggesting that virulent infections also occur in natural hosts. Based on these findings, the present study aimed to explore, whether and to which extent other native bird species are possibly affected by pathogenic haemosporidian lineages, contributing to avian morbidity. Carcasses of passerine birds and woodpeckers were collected during a citizen science-based survey for avian mortality in Austria, from June to October 2020. Tissue samples were taken and examined for haemosporidians of the genera Plasmodium, Haemoproteus and Leucocytozoon using PCR and sequencing, histology, and chromogenic in situ hybridization applying Haemosporida-specific probes. From over 160 dead bird reportings, 83 carcasses of 25 avian species were submitted for investigation. Overall haemosporidian prevalence was 31%, with finches and tits prevailing species counts and infections. Sequence analysis revealed 18 different haplotypes based on partial cytochrome b gene (four Plasmodium, four Haemoproteus, ten Leucocytozoon), including five novel Leucocytozoon lineages. Most infected birds presented low parasite burdens in peripheral blood and tissues, ruling out significant contribution of haemosporidial infection to morbidity or death of the examined birds. However, two Great tits showed signs of avian malaria, suggesting pathogenic effects of the detected species P. relictum SGS1 and P. elongatum GRW06. Further, exo-erythrocytic stages of several haemosporidian lineages were detected. While suggesting generally little contribution of haemosporidial infection to mortality of the investigated bird species, the findings indicate a possible role of certain haemosporidian lineages in overall clinical manifestation, either as main causes or as concurrent disease agents. Further, the study presented new data on exo-erythrocytic stages of previously reported lineages and illustrated how citizen science can be used in the field of haemosporidian research.