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A novel avian trypanosome, Trypanosoma culicavium sp. nov., isolated from Culex mosquitoes, is described on the basis of naturally and experimentally infected vectors and bird hosts, localization in the vector, morphological characters and molecular data. This study provides the first comprehensive description of a trypanosome species transmitted by mosquitoes, in which parasites form plugs and rosettes on the stomodeal valve. Trypanosomes occurred as long epimastigotes and short trypomastigotes in vectors and culture and as long trypomastigotes in birds. Transmission of parasites to bird hosts was achieved exclusively by ingestion of experimentally infected Culex mosquito females by canaries (Serinus canaria), but not by Japanese quails (Coturnix japonica), nor by the bite of infected vectors, nor by ingestion of parasites from laboratory cultures. Transmission experiments and the identity of isolates from collared flycatchers (Ficedula albicollis) and Culex mosquitoes suggests that the natural hosts of T. culicavium are insectivorous songbirds (Passeriformes). Phylogenetic analyses of small-subunit rRNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase gene sequences demonstrated that T. culicavium sp. nov. is more related to Trypanosoma corvi than to other avian trypanosomes (e.g. Trypanosoma avium and Trypanosoma bennetti).

Induction of penetration gland emptying by cercariae of the bird schistosomes Trichobilharzia szidati and T. regenti employing linoleic acid, linolenic acid, praziquantel and calcium ionophore A23187 showed that both postacetabular and circumacetabular cells released their content at chosen stimulant concentrations. The gland secretions consisted of soluble and insoluble parts. The former one adhering to the ground seemed to have different saccharide composition from the glands of Schistosoma mansoni. It bound labelled saccharides, thus exhibiting lectin-like activity. Protein profiles of the latter one were identical after stimulation by all four stimulants in T. szidati. The soluble secretions contained several proteolytic enzymes; 31 kDa and 33 kDa cysteine proteases were identified in E/S products of T. szidati and T. regenti, respectively. The circumacetabular glands contained a significant amount of calcium. Immunohistochemistry revealed that the origin of E/S products after in vitro stimulation is in both penetration glands and tegumental structures. No crossreactivity was observed between the bird schistosomes and a serum raised against S. mansoni elastase.

Three strains of a trypanosomatid protozoan were isolated from the midguts of two naturally infected species of biting midges [Culicoides (Oecacta) festivipennis and Culicoides (Oecacta) truncorum] and characterized by light and electron microscopy and by molecular techniques. Morphological characteristics and sequences of the 18S rRNA, 5S rRNA, spliced leader RNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase genes indicate that the studied flagellates represent a novel phylogenetic lineage within the Trypanosomatidae. Based on phylogenetic analyses, the novel endosymbiont-free, monoxenous trypanosomatid was classified as Sergeia podlipaevi gen. nov., sp. nov. Interestingly, it is closely related to another trypanosomatid species that parasitizes the sand fly Lutzomyia evansi, a blood-sucking dipteran from South America. The type strain of S. podlipaevi sp. nov., ICUL/CZ/2000/CER3, was obtained from Malpighian tubes. Of 2518 females of seven species of biting midges trapped in the Czech Republic, more than 1.5 % were infected by trypanosomatid parasites. An unrelated insect species, Culicoides (Monoculicoides) nubeculosus, was experimentally infected with S. podlipaevi, demonstrating that its host range extends to different subgenera of biting midges.