First Report of (Filarioidea) in Mute Swan () in Poland - the Case Report.

Mute swans () of the Anatidae family are common in wetlands of Europe. They winter in Africa, Asia and some parts of Europe. The species is exposed to many pathogens in its places of residence, including parasites possibly introduced from tropical countries by other species of birds that take long wanderings and occupy a similar ecological niche. One such case is the infection of the , nematode belonging to the Filarioidea family. It invades the bird's myocardium and, according to some authors, this nematode may be one of the main causes of swans' deaths. The material for the present study was an approximately 2 year old female mute swan, which during the flight fell suddenly to the ground in Pomorskie Voivodeship (Poland, 53°50'18″N 18°12'54″E) in November. During the examination and medical observation, weakness, diarrhea and infestation with lice were found. The cause of its eventual death was attributed to a failure of the circulatory system. Post mortem, two abscesses with diameters of 2-3 cm were found in its liver parenchyma. Three nematodes were visible in the epicardium and many more in myocardium. Upon cutting open the heart, small yellowish foci, about 1 mm in diameter were scattered over valves. On the basis of morphological features, infection by was concluded. As far as we are aware, in Poland there were no earlier reports of this parasite infecting a swan.