Metatranscriptomic Survey Reveals Unexpected Presence of Parainfluenza Virus 5 in Field Populations of Pyrrhocoris apterus

Abstract The firebug, Pyrrhocoris apterus, is a widespread insect species found in Europe and Asia. It lives in colonies and can often be found in the spaces between stones and around seed plants during the summer months. This study used high-throughput sequencing (HTS) data to screen for virus-associated sequences in P. apterus nymphs and adults collected from areas with Tiliaceae and Malvaceae plants in Erzurum (two different localities, E1 and E2) and Istanbul (I1), Türkiye, between August and October 2025. The results revealed that a significant portion of the Parainfluenza virus 5 (PIV5) genome was present in the samples. This included genes encoding the nucleoprotein (NP), V protein (V), matrix protein (M), fusion protein (F), haemagglutinin-neuraminidase (HN), and part of the large protein (L). Notably, the E2 population consisted of nymphs, while the E1 and I1 populations consisted of adults. Coverage values were found to be 76.307, 32.940, and 9.643 for the E1, E2, and I1 populations, respectively. A BLAST nucleotide analysis of the complete NP, V, M, F, and HN gene concatenated sequences revealed 99.82, 99.82, and 99.47% similarity for populations E1, E2, and I1, respectively, with PIV5 (accession number KX060176), which was isolated from Homo sapiens in the USA. In the phylogenetic tree drawn by consecutively adding the amino acid sequences of five genes whose sequences were fully obtained, all three samples were placed in group 3. To our knowledge, no studies have demonstrated the natural presence of PIV in insects. Apart from vertebrate hosts, they have only been identified in ticks in north-east China. A significant portion of the PIV5 genome, with high coverage values, was detected in P. apterus samples collected from different geographical populations. This suggests that the virus is associated with these insects, rather than the finding being due to random laboratory contamination.