Europe-wide distribution and bat-host specific lineages in the malarial parasite Polychromophilus murinus revealed through genetic screening of bat flies

Malaria parasites of the genus Polychromophilus commonly infect vespertilionid and miniopterid bats, and are transmitted by bat flies (Nycteribiidae). While Polychromophilus murinus has been recorded sporadically in Europe, its host range, distribution and phylogeographic structure have not been explored. Here we investigate the prevalence and genetic diversity of P. murinus infections in 1131 bat flies collected from seven European bat species, focusing on Basilia nana, collected from its primary host, the Bechstein's bat throughout its distribution. Additionally, we explore the temporal dynamics of P. murinus in two regions in Germany where bat flies were repeatedly collected over at least five years. Bat flies were screened for Polychromophilus infection via PCR of a fragment of cytochrome b, and fragments of three additional genes were sequenced for positive samples. Overall, P. murinus infections were detected in 287 of 1131 screened bat flies of four different species, collected from seven bat species, across 13 countries. The 269 recovered cytb sequences represented 21 distinct haplotypes, clustered based on the bat species from which the infected flies were collected. Repeated sampling over multiple years revealed a consistent presence of P. murinus in both investigated populations, without substantial variation in prevalence between years. The results suggest an endemic long-term presence of Polychromophilus within European bat populations, and the presence of host-specific associations between P. murinus lineages and its various bat hosts. We posit that exposure to P. murinus appears to be a near certainty in several European bat species, and its potential costs should be further investigated.