Specific status and pathogenicity of syngamid nematodes in bird species (Ciconiformes, Falconiformes, Gruiformes) from Germany.

A total of 549 birds from four orders were examined for nematodes in their respiratory system from 1995 to 2000. Twelve individuals of Falconiformes (n = 503), one of Gruiformes (n = 22) and one of Ciconiformes (n = 1), but no bird of the order Strigiformes (n = 23) were infected with syngamids. The syngamid species included Hovorkonema variegatum, Syngamus trachea and Cyathostoma trifurcatum from the trachea, bronchi and air sacs, with H. variegatum being the most prevalent. Cyathostoma trifurcatum from a black stork Ciconia nigra is a new record for Germany. The marsh harrier Circus aeruginosus and the white-tailed sea eagle Haliaeetus albicilla are new hosts for H. variegatum. Morphological characters such as the dorsal rays of the bursa copulatrix, length of the spicules and the mouth capsule are used to differentiate species of the family Syngamidae. Egg size is different between S. trachea and H. variegatum. In addition to morphological characters, the nucleotide sequence of the SSU ribosomal gene was determined for H. variegatum. Pairwise comparisons with the SSU sequence of S. trachea (AF036606) revealed sequence difference of 2.6%. The nucleotide sequence of the second internal transcribed spacer of ribosomal DNA for different populations of H. variegatum was also determined. Pairwise comparisons revealed two separate strains with a sequence difference of 14.0% to 14.5% suggesting the existence of a cryptic species. Pathological findings associated with H. variegatum were found in 7 of 12 cases and consisted of thickened air sac walls and lesions or granuloma at the site of attachment of the worm, which occasionally involved the underlaying tissues. Lymphoplasmocytic air sacculitis was the most prominent histological lesion found.