Diplotriaena obtusa infection in an Eurasian blue tit (Cyanistes caeruleus) in Germany. Pathology and phylogenetic analysis

Diplotriaena obtusa is a nematode found in air sacs of a wide number of birds, including Passerine species. During a period of increased mortality of blue tits (Cyanistes caeruleus) in Germany, we collected adult nematode worms from the air sacs of a deceased male blue tit. The nematodes showed morphological features consistent with Diplotriaena ssp. A polymerase chain reaction (PCR) assay targeting the small subunit (SSU) 18S rRNA gene identified the parasite species as Diplotriaena obtusa. Phylogenetic analysis confirmed species identification. Further examinations against infectious pathogens like Suttonella ornithocola, Salmonella spp., Pasteurella spp., Chlamydia spp., Influenza A virus, Usutu virus and West Nile virus were negative. This is the first report of D. obtusa in a blue tit from Germany.