Malaria and related haemosporidioses in wild birds: Common but underestimated causes of avian mortality?

Avian haemosporidia are blood parasites of birds that are transmitted by arthropod vectors. Three genera are known to infect birds, Plasmodium, Haemoproteus and Leucocytozoon, each of them containing numerous species. They occur throughout the world - except in the circumpolar regions - and infect a large proportion of wild birds. It has long been assumed that coevolution of parasite and host has resulted in perfect adaptation that prevents the hosts from becoming sick. When birds from cold climates are transferred to warmer regions they become infected and frequently suffer from severe disease (avian malaria) or even die. There is increasing evidence that wild birds native to the distribution areas of the parasites more frequently develop severe disease and even die due to malaria than previously assumed.

We believe that avian haemosporidioses (including avian malaria) are grossly underestimated causes of severe diseases and mortalities in wild birds. There is a lack of comprehensive studies on wild bird mortalities and a lack of suitable methods for visualizing parasites of the different genera, subgenera and species of haemosporidians in samples of dead birds. We also believe that the variety of haemosporidian species with high virulence for certain species of wild as well as cage and aviary birds is wider than currently assumed. This is because the tissue stages of these parasites are morphologically similar and there are no tools that allow the exact identification of these parasites in tissue samples of dead birds, particularly in the case of mixed infections.

We plan to test these ideas by “visualizing ” defined genera and species of haemosporidia in tissue samples. This is intended with the aid of in situ hybridization using oligonucleotide probes against ribosomal RNA sequences. The sequences of the rRNA genes are largely unknown and need to be established by suitable amplification and sequencing strategies in unequivocal reference material.

Project staff:
Univ.-Prof. Dr. Herbert Weissenböck, PI 1

Dr. Josef Harl, Postdoc 2
MMag. Tanja Himmel PhD 3
Cooperation partners:
Dr. Gediminas Valkiunas, Nature Research Centre, Vilnius, Litauen 4
A.o. Prof. Dr. Alexandra Scope, Clinical Unit of Medicine Small Animals, Vetmed.Uni.Vienna 5
Univ.-Prof. Dr. Leonida Fusani, KLIVV, Vetmed.Uni.Vienna 6

Project period: 03/2017 - 03/2020

FWF - Austrian Science Fund 7


Haemosporidioses in wild Eurasian blackbirds (Turdus merula) and song thrushes (T. philomelos): an in situ hybridization study with emphasis on exo-erythrocytic parasite burden.
Tanja Himmel, Josef Harl, Simone Pfanner, Nora Nedorost, Norbert Nowotny, Herbert Weissenböck
Malaria Journal 2020; 19:69
Link: 8

Molecular probes for the identification of avian Haemoproteus and Leucocytozoon parasites in tissue sections by chromogenic in situ hybridization
Tanja Himmel, Josef Harl, Anna Kübber‑Heiss, Cornelia Konicek, Nuhacet Fernández, Carles Juan‑Sallés,
Mikas Ilgūnas, Gediminas Valkiūnas, Herbert Weissenböck
Parasites & Vectors2019; 12:282
Link: 9

The nuclear 18S ribosomal DNAs of avian haemosporidian parasites
Josef Harl, Tanja Himmel, Gediminas Valkiūnas, Herbert Weissenböck Malaria Journal 2019; 18:305
Link: 10



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