Trypanosoma culicavium sp. nov., an avian trypanosome transmitted by Culex mosquitoes

Abstract

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).

A comparative molecular and 3-dimensional structural investigation into cross-continental and novel avian Trypanosoma spp. in Australia

“…Before its formal description T. thomasbancrofti was found in a number of birds in Europe [8]. This is the first report of T. culicavium in Australia, which was identified in Culex mosquitos and the collared flycatcher ( Ficedula albicollis ) in central Europe [33]. A currently unnamed isolate from the group designated Trypanosoma spp.…”

“…A possible reason for the relatively conserved number of avian trypanosomes include a high level of vectorial specificity, thus involving invertebrate species that are very common and occur on all continents. However, at this stage little is known of the vectors in Australia [9, 61], while avian trypanosome vectors are considered to be biting flies or mosquitos elsewhere in the world [26, 33]. In Australia, leeches [14], biting flies [15], and ticks [62] have been suggested most frequently in the literature as vector candidates for avian trypanosomes.…”

“…Three morphotypes were observed of Trypanosoma sp. AAT and both epimastigote forms were significantly larger than T. corvi epimastigotes [7, 33]. T. corvi had one epimastigote (19 ± 2 μm) when grown in culture [33], while a description from bone marrow identified a number of morphotypes including epimastigotes (shorter than 20 μm) with tapered ends, and trypomastigotes [7].…”

“…Trypanosoma sp. AAT kDNA appear most similar to T. corvi and T. culicavium , and were less similar to those of T. avium or T. thomasbancrofti , which are much stouter in TEM micrographs [13, 26, 33]. The kDNA width of Trypanosoma sp.…”

“…Some trypanosomes isolated from birds such as T. avium possess what appears to be a unique kinetoplast, with unusually large minicircles [26, 31, 32] that make them intrinsically important tool in trying to understand kinetoplastid evolution and biology. As a result of the pleomorphism of avian trypanosomes within species, it has been suggested that in vitro investigations may be more reliable when trying to characterise their structure and understand the differences between species as in vitro studies provide a more stable environment [6, 33]. …”