More than 160 species of nematodes of the Onchocercidae family are known to parasite birds. There are reports of haematozoa infecting passerines in tropical and neotropical regions of South America. In Argentina, reports of microfilariae presence on blood of birds are scarce. Taxonomic identification of the filarial worms is achieved by means of themorphologic exam of the adult parasite and confirmed by molecular techniques. However, is not always possible to obtain the adult stage, due to their location on their host, many times hard to find, even on certain situations when there is access to ...