Avian haemosporidian diversity and transmission across birds and mosquitoes in Botswana

Avian malaria parasites circulate globally among birds and their dipteran vectors, yet their diversity and transmission dynamics remain poorly characterised in sub-Saharan Africa. Here, we investigated haemosporidian infections in birds and mosquitoes across Botswana, where resident and migratory bird species interact with diverse vector communities. We screened 395 birds from 23 genera and 65 species and 1,425 mosquitoes from eight genera and 28 species for Plasmodium , Haemoproteus and Leucocytozoon . We detected a high level of parasite diversity, identifying 40 lineages in birds, 31 in mosquitoes, including one lineage shared between the avian hosts and vectors. A total of 36 lineages were newly described. The detection of the African Plasmodium lineage MALNI02 in both birds and multiple mosquito taxa, provides the first evidence of its potential transmission pathway between avian hosts and vectors in Africa. Several cosmopolitan lineages previously known from Europe were detected in both resident and migratory birds and in mosquitoes. This suggests that migratory birds may help to spread these haemosporidian parasites across continents, and that African mosquito taxa can transmit them. It also indicates that infections previously detected in Europe can circulate among resident bird species in Africa. These findings support the idea of cross-transmission between resident and migratory bird species and highlight the importance of southern Africa in understanding avian malaria transmission across the African-Eurasian flyway. • High diversity of haemosporidian parasites detected in both birds and mosquitoes in Botswana. • Migratory birds may introduce cosmopolitan lineages, which can infect local mosquitoes and be carried by resident bird species. • First evidence of potential vectors for Plasmodium MALNI02 in multiple African mosquito taxa. • Local Culex species play a key role in facilitating parasite transmission within and among migratory and resident bird species.