Avian Haemosporida in mosquitoes collected in Germany

Abstract text

Avian Haemosporida are a diverse group of protozoan blood parasites found worldwide, except at the poles. In Germany, several studies have demonstrated high infection prevalences with the haemosporidian genera Plasmodium, Haemoproteus and Leucocytozoon in birds, but little information exists about their specific native vectors. Mosquitoes are the main vectors of avian Plasmodium-species, which are responsible for the deaths of numerous exotic (= immunologically naïve) birds in zoos, every year, while native birds are adapted to the parasites and largely protected by an effective immune response. In the presented study, mosquitoes were trapped in bird/animal parks and riverine floodplains, and aspirated in gardens from 2020 to 2022. Mosquito females were pooled with up to 10 specimens according to species, location and date. Extracted DNA was screened for avian Haemosporida-specific mitochondrial rDNA using a realtime-PCR. Positive samples were amplified by a Plasmodium/Haemoproteus-specific nested PCR targeting the partial cytochrome b gene for species identification. Of 2,632 pools with 8,841 female mosquitoes, reactions of 47 pools confirmed an infection. The results show the occurrence of H. majoris (n = 1) as well as several Plasmodium species: P. relictum (n = 17), P. matutinum (n = 13), P. vaughani (n = 10), P. circumflexum (n = 3), P. cathemerium (n = 1) and Plasmodium sp. (n = 2). The parasites were detected in three different mosquito species groups: Cx. pipiens s.l. (n = 40), Cs. morsitans/fumipennis (n = 6) and Ae. cinereus/geminus (n = 1). Although the overall pool infection prevalence (1.8 %) appears to be low compared to a study from neighbouring Austria (6.4 %), the minimum infection rate is higher in the present study (5.3 vs. 3.7 in Austria). We not only demonstrated the ongoing circulation of Plasmodium and Haemoproteus parasites in the German mosquito population but show, for the first time, the presence of P. cathemerium in field-collected mosquitoes in Germany.