ORIGINAL PAPER Microfilariae in birds in the Czech Republic, including a note on adult nematodes Eufilaria delicata in a song thrush Turdus philomelos Martina Haas & Vlastimil Baruš & Václav Benedikt & Ivan Literák Received: 15 November 2010 / Accepted: 15 February 2011 / Published online: 12 March 2011 # Springer-Verlag 2011 Abstract Blood samples of more than 1,100 passerineform birds of 40 species were investigated for the occurrence of microfilariae. In the year 2005, 3 out of 677 birds of 31 species (prevalence 0.4%) were infected with microfilariae during the post-nesting period. During the pre-nesting period in the year 2007, 11 out of 438 birds of 31 species were infected with microfilariae (prevalence 2.5%). Both the pre-nesting and post-nesting examinations were con- ducted at the same location in the northeastern part of the Czech Republic. The microfilariae of the Eufilaria delicata and Ornithofilaria mavis species were found in Turdus merula, Turdus philomelos, and Erithacus rubecula (Pass- eriformes, Turdidae). Single individual of Poecile montanus (Passeriformes, Paridae) was infected with undetermined microfilariae. The morphometric variability of microfilariae found in T. philomelos, E. rubecula, and Poecile montanus were recorded. Infections caused by microfilariae E. delicata were more frequent than infections caused by O. mavis. Seven adult nematodes E. delicata were found in a subcutaneous cyst on the heel joint in one T. philomelos, which is the first record of adult E. delicata nematodes in birds in the Czech Republic. Introduction The filariid nematodes are viviparous and produce their larval stages (microfilariae) in the bloodstream (Keymer 1982). While microfilariae of Eufilaria delicata Supperer, 1958 and Ornithofilaria mavis Leiper, 1909 (Nematoda: Filarioidea) readily occur in birds in Europe, occurrence of the adult stages of these nematodes is rare (Sonin 1966; Kučera 1982; Baruš 1992; Hauptmanová 2003; Votýpka et al. 2003; Hauptmanová et al. 2004; Palinauskas et al. 2005). They are known to be transmitted by dipterans including genera Simulium and Culicoides (Anderson 2000). Adult filariids of the genus Eufilaria Seurat, 1921 (Lemdaniinae) are mostly found in subcutaneous tissue around the larynx, esophagus, and crop, and also in subcutaneous tissue of the leg joints (Anderson 2000; Bartlett 2008). E. delicata adults and microfilariae have been recorded in passerine birds (Passeriformes) of the genus Turdus (Turdidae) in Austria and France (Supperer 1958; Bain 1980), in Garrulus glandarius (Passeriformes, Corvidae) in Austria (Supperer 1958), and Corvus frugile- gus (Corvidae) in Moldavia (Sonin 1966). Findings of microfilariae have also been recorded in Spain in Turdidae (López-Caballero 1978a). M. Haas (*) : V. Benedikt : I. Literák Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, Palackého 1–3, 612 42 Brno, Czech Republic e-mail: haas.2m@gmail.com M. Haas Institute of the High Mountain Biology, University of Zilina, 059 56 Tatranska Javorina 7, Slovak Republic V. Baruš Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Kamýcká 957, 165 21 Prague 6–Suchdol, Czech Republic Parasitol Res (2011) 109:645–655 DOI 10.1007/s00436-011-2297-4