Host specificity of avian malaria parasites
Birds are hosts of a stunning diversity of malaria (Plasmodium) and related haemosporidan parasites (Haemoproteus and Leucocytozoon). Bird haemosporidians have a life cycle that is similar to human malaria parasites; the asexual replication takes place in blood or tissues of the vertebrate host whereas the sexual phase takes place in various blood-sucking insects such as mosquitoes, biting midges and blackflies. A few hundred species of bird haemosporidians have been described morphologically but the molecular analyses suggest that the true number of species probably counts in thousands. The highest species diversity is found in the tropics but transmission commonly happens as far north as in Sweden. A particular concern is that a warmer climate may allow tropical parasites to expand their ranges and infect European resident species which have not encountered these parasites before, potentially posing substantial threats to these populations.
We are primarily interested in understanding why the parasites vary in their levels of host specificity. Most of the parasites are specific to one or a few closely related host species but some are able to infect more than 100 species of birds. We identify the parasites by BarCoding (PCR and DNA sequencing) and use our freely available database MalAvi to relate the findings to morphologically identified species, host range and geographic distribution. We have recently sequenced the genome of Haemoproteus tartakovskyi, allowing us to address questions on population structure and species limits of the parasites, which require multiple nuclear genetic markers. The genomic resources will also help resolving the enigmatic phylogenetic relationship within the group of Haemosporidian parasites.
To find out the virulence of the parasites we carry out controlled infection experiments with wild birds in captivity in collaborations with researchers at the Nature Research Centre in Vilnius, Lithuania. This enables us to monitor the complete infection episode from primary infection to chronic stages, measuring host responses in multiple ways including telomere loss rate. We also study the impact and dynamic of bird malaria in several species in the wild, particular in a long term study of great reed warblers at lake Kvismaren and in a community of forest living passerine birds at lake Krankesjön.