Culicoides (Diptera: Ceratopogonidae) biting midges are a diverse group of insect vectors that transmit pathogens affecting humans, livestock, and wild animals. Among them, Oropouche virus, African Horse sickness virus, and bluetongue virus are the most notable pathogens. However, comparatively little is known about which Culicoides species serve as vectors of wildlife parasites affecting wild birds globally, including the malaria-like parasite of the genus Haemoproteus (Haemosporida: Haemoproteidae) and kinetoplastid Trypanosoma (Trypanosomatida: Trypanosomatidae). Beyond the direct impact of their bites, infections by these parasites negatively affect wild birds from early developmental stages, significantly influencing their ecology and evolution. Here, we present a comprehensive review of the role of Culicoides species in the transmission of these two genera of avian parasites in Europe: Haemoproteus and Trypanosoma. We identify key information and methods used to study Culicoides-bird-parasite interactions, from insect sampling to vector competence assessment. Additionally, we highlight key knowledge gaps and propose future research directions in this area.

• Keywords
• Culicoides, Haemoproteus, Trypanosoma, Avian malaria, Birds, Blood parasites, Vectors,
• MeSH
• Ceratopogonidae * parasitology   physiology   MeSH
• Animals, Wild parasitology   MeSH
• Haemosporida physiology   isolation & purification   MeSH
• Insect Vectors * parasitology   MeSH
• Bird Diseases * transmission   parasitology   epidemiology   MeSH
• Protozoan Infections, Animal * transmission   parasitology   epidemiology   MeSH
• Birds * parasitology   MeSH
• Trypanosoma physiology   isolation & purification   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Geographicals
• Europe epidemiology   MeSH

Avian trypanosomes (Trypanosoma, Kinetoplastea) are successful blood parasites occurring worldwide. These parasites are usually non-pathogenic to their avian hosts, thus neglected in studies regarding their life cycles and vectors. Several families of blood-sucking dipteran insects, including mosquitoes, have been identified as vectors of avian trypanosomes. Mosquitoes have been experimentally confirmed as vectors of Trypanosoma culicavium and Trypanosoma thomasbancrofti. In this study, we describe a third species of avian trypanosomes occurring in mosquitoes, designated as Trypanosoma tertium n. sp. This species can be distinguished from related trypanosome species based on morphology and small subunit rRNA gene sequence. Two isolates of T. tertium n. sp. obtained from a mosquito and a bird host were able to infect two subspecies of laboratory Culex pipiens mosquitoes, with infection rates reaching 60% and heavy infections in 90% of positive females. In infected mosquitoes, trypanosomes occurred as long epimastigotes in the midgut and short epimastigotes and rosettes in the hindgut. Putative infectious stages were detected in the diuretic liquid of infected mosquitoes, suggesting, besides transmission through ingestion of the infected vector, a possible transconjunctival infection. Among wild mosquitoes, avian trypanosomes were detected exclusively in Cx. pipiens with 3.3% total prevalence, while T. tertium n. sp. prevalence was only 0.08% among 1128 dissected Cx. pipiens individuals. In birds, T. tertium n. sp. was detected in 8 species within which the prevalence was 1.3% (686 birds), while it was 0.3% in total (3084 birds). We discuss the relationship of the newly described T. tertium n. sp. with other mosquito-transmitted trypanosomes.

• Keywords
• Culex, avian blood parasite, monoxenous Kinetoplastea, morphology, phylogeny, transmission, vector,
• MeSH
• Culex * parasitology   MeSH
• Phylogeny MeSH
• Mosquito Vectors * parasitology   MeSH
• Bird Diseases * parasitology   epidemiology   transmission   MeSH
• Prevalence MeSH
• Trypanosoma * genetics   isolation & purification   classification   growth & development   MeSH
• Trypanosomiasis * veterinary   parasitology   epidemiology   transmission   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

BACKGROUND: A high prevalence of parasites may result from life-long persistence of infection or from high reinfection rates. We have studied blood parasites in a breeding population of the accipitrid raptor, Eurasian sparrowhawk (Accipiter nisus), to determine parasite diversity and turnover. METHODS: During this 7-year study, 210 adult Eurasian sparrowhawks breeding in the city of Prague were checked for parasites using several diagnostic methods. RESULTS: In both female and male raptors, parasites of the genus Leucocytozoon were the most prevalent (92% and 85%, respectively) followed in decreasing order of prevalence by those of genus Trypanosoma (74% and 68%, respectively) and genus Haemoproteus (46% and 16%, respectively). The prevalence of all parasites increased with age in both sexes, with the females at each respective age having the higher prevalence. There was a positive association between Haemoproteus and Leucocytozoon infections. Persistence at the individual level was higher than incidence for Trypanosoma and Haemoproteus. In the case of Leucocytozoon and Trypanosoma, most individuals probably become infected in their first year of life or even before dispersal from the nest. The detected parasites belonged to Trypanosoma avium sensu stricto, Leucocytozoon sp. (haplotypes ACNI1 and ACNI3) and Leucocytozoon mathisi (haplotype ACNI4) and two new lineages of the Haemoproteus elani complex (ACCNIS6 and ACCNIS7). Detailed analysis of parasite lineages in individuals that were repeatedly sampled revealed lineage turnover that would otherwise remain hidden. Phylogenetic analysis revealed that the detected Haemoproteus belongs to a phylogenetically distant group whose taxonomic position requires further analysis. CONCLUSIONS: All three genera of blood parasites persist in infected individuals, thus enabling sustainability of vector transmission cycles. Prevalence increases with age; however, there is a high turnover of Leucocytozoon lineages. No clear evidence of parasite-induced mortality was found, and most of the individuals were infected early in life, particularly in the case of Leucocytozoon.

• Keywords
• Avian blood parasite, Birds of prey, Haemosporida, Parasite persistence, Raptor, Trypanosoma avium, Trypanosoma bennetti, Trypanosoma corvi,
• MeSH
• Phylogeny MeSH
• Haemosporida * genetics   MeSH
• Incidence MeSH
• Hawks * parasitology   MeSH
• Bird Diseases * parasitology   MeSH
• Prevalence MeSH
• Protozoan Infections, Animal * parasitology   MeSH
• Trypanosoma * genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Louse flies (Hippoboscidae) are permanent ectoparasites of birds and mammals. They have a cosmopolitan distribution with more than 200 described species. The aim of this study was to reveal host-vector-parasite associations between louse flies, birds, and trypanosomes. A total of 567 louse fly specimens belonging to 7 species were collected from birds at several localities in Czechia, including the rare species Ornithophila metallica and Ornithoica turdi. There was a significant difference in the occurrence of Ornithomya avicularia and Ornithomya fringillina on bird hosts according to their migratory status, O. fringillina being found more frequently on long-distance migrants. Trypanosomes were found in four species, namely, Ornithomya avicularia, O. fringillina, O. biloba, and Ornithoica turdi; the later three species are identified in this paper as natural trypanosome vectors for the first time. The prevalence of trypanosomes ranged between 5 and 19%, the highest being in O. biloba and the lowest being in O. fringillina. Phylogenetic analysis of the SSU rRNA gene revealed that a vast majority of trypanosomes from hippoboscids belong to the avian T. corvi/culicavium group B. Four new lineages were revealed in group B, with louse flies being probable vectors for some of these trypanosome lineages. We also confirmed the transcontinental distribution of several trypanosome lineages. Our results show that hippoboscids of several genera are probable vectors of avian trypanosomes.

• Keywords
• Hippoboscidae, Ornithoica, Ornithomya, Ornithophila, Trypanosoma, avian parasite, host specificity, transmission,
• Publication type
• Journal Article MeSH

Avian trypanosomes are cosmopolitan and common protozoan parasites of birds; nevertheless, knowledge of their life cycles and vectors remains incomplete. Mosquitoes have been confirmed as vectors of Trypanosoma culicavium and suggested as vectors of T. thomasbancrofti; however, transmission has been experimentally confirmed only for the former species. This study aims to confirm the experimental transmission of T. thomasbancrofti to birds and its localization in vectors. Culex pipiens were fed on blood using four strains of T. thomasbancrofti, isolated from vectors and avian hosts; all strains established infections, and three of them were able to develop high infection rates in mosquitoes. The infection rate of the culicine isolates was 5-28% for CUL15 and 48-81% for CUL98, 67-92% for isolate OF19 from hippoboscid fly, while the avian isolate PAS343 ranged between 48% and 92%, and heavy infections were detected in 90% of positive females. Contrary to T. culicavium, trypanosomes were localized in the hindgut, where they formed rosettes with the occurrence of free epimastigotes in the hindgut and midgut during late infections. Parasites occurred in urine droplets produced during mosquito prediuresis. Transmission to birds was achieved by the ingestion of mosquito guts containing trypanosomes and via the conjunctiva. Bird infection was proven by blood cultivation and xenodiagnosis; mature infections were present in the dissected guts of 24-26% of mosquitoes fed on infected birds. The prevalence of T. thomasbancrofti in vectors in nature and in avian populations is discussed in this paper. This study confirms the vectorial capacity of culicine mosquitoes for T. thomasbancrofti, a trypanosome related to T. avium, and suggests that prediuresis might be an effective mode of trypanosome transmission.

• Keywords
• Culex, Trypanosoma thomasbancrofti, avian parasite, life cycle, mosquito, prediuresis, transmission,
• Publication type
• Journal Article MeSH

Trypanosomatid flagellates have not been studied in Austria in any detail. In this study, specific nested PCR, targeted on the ribosomal small subunit, was used to determine the occurrence and diversity of trypanosomatids in wild-caught mosquitoes sampled across Eastern Austria in the years 2014-2015. We collected a total of 29,975 mosquitoes of 19 species divided in 1680 pools. Of these, 298 (17.7%), representing 12 different mosquito species, were positive for trypanosomatid DNA. In total, seven trypanosomatid spp. were identified (three Trypanosoma, three Crithidia and one Herpetomonas species), with the highest parasite species diversity found in the mosquito host Coquillettidia richiardii. The most frequent parasite species belonged to the mammalian Trypanosoma theileri/cervi species complex (found in 105 pools; 6.3%). The avian species T. culicavium (found in 69 pools; 4.1%) was only detected in mosquitoes of the genus Culex, which corresponds to their preference for avian hosts. Monoxenous trypanosomatids of the genus Crithidia and Herpetomonas were found in 20 (1.3%) mosquito pools. One third (n = 98) of the trypanosomatid positive mosquito pools carried more than one parasite species. This is the first large scale study of trypanosomatid parasites in Austrian mosquitoes and our results are valuable in providing an overview of the diversity of these parasites in Austria.

• MeSH
• Biodiversity MeSH
• Culicidae parasitology   MeSH
• Phylogeny MeSH
• DNA, Protozoan MeSH
• DNA, Ribosomal MeSH
• Sequence Analysis, DNA MeSH
• Trypanosoma classification   genetics   MeSH
• Trypanosomiasis parasitology   transmission   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Austria MeSH
• Names of Substances
• DNA, Protozoan MeSH
• DNA, Ribosomal MeSH

The prevalences of heteroxenous parasites are influenced by the interplay of three main actors: hosts, vectors, and the parasites themselves. We studied blood protists in the nesting populations of raptors in two different areas of the Czech Republic. Altogether, 788 nestlings and 258 adult Eurasian sparrowhawks (Accipiter nisus) and 321 nestlings and 86 adult common buzzards (Buteo buteo) were screened for parasites by the microscopic examination of blood smears and by cultivation. We examined the role of shared vectors and parasite phylogenetic relationships on the occurrence of parasites. In different years and hosts, trypanosome prevalence ranged between 1.9 and 87.2 %, that of Leucocytozoon between 1.9 and 100 %, and Haemoproteus between 0 and 72.7 %. Coinfections with Leucocytozoon and Trypanosoma, phylogenetically distant parasites but both transmitted by blackflies (Simuliidae), were more frequent than coinfections with Leucocytozoon and Haemoproteus, phylogenetically closely related parasites transmitted by different vectors (blackflies and biting midges (Ceratopogonidae), respectively). For example, 16.6 % buzzard nestlings were coinfected with Trypanosoma and Leucocytozoon, while only 4.8 % with Leucocytozoon and Haemoproteus and 0.3 % with Trypanosoma and Haemoproteus. Nestlings in the same nest tended to have the same infection status. Furthermore, prevalence increased with the age of nestlings and with Julian date, while brood size had only a weak negative/positive effect on prevalence at the individual/brood level. Prevalences in a particular avian host species also varied between study sites and years. All these factors should thus be considered while comparing prevalences from different studies, the impact of vectors being the most important. We conclude that phylogenetically unrelated parasites that share the same vectors tend to have similar distributions within the host populations of two different raptor species.

• MeSH
• Raptors parasitology   MeSH
• Falconiformes parasitology   MeSH
• Phylogeny MeSH
• Haemosporida classification   genetics   isolation & purification   physiology   MeSH
• Insect Vectors parasitology   physiology   MeSH
• Host Specificity MeSH
• Bird Diseases epidemiology   parasitology   transmission   MeSH
• Prevalence MeSH
• Protozoan Infections, Animal epidemiology   parasitology   transmission   MeSH
• Birds parasitology   MeSH
• Simuliidae parasitology   physiology   MeSH
• Trypanosoma classification   genetics   isolation & purification   physiology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic epidemiology   MeSH

Trypanosomes identified as Trypanosoma avium were found in the ornithophilic black flies ( Eusimulium latipes) attacking buzzard nestlings ( Buteo buteo). Parasites formed plugs and rosettes in the hindgut of the vector and were attached on the cuticular lining of the black fly anterior intestine (ileum) by hemidesmosome-like plaques. Hindgut stages from infected black flies were experimentally transmitted into canaries ( Serinus canaria) by ingestion of vectors and by contamination of host conjunctiva. This is the first clear evidence of such transmission in avian trypanosomes. Parasites survived in peripheral blood of birds at the least 10 months. In contrast to the direct inoculation of insect stages, parasites from culture failed to produce infection in experimental birds; this has consequences for laboratory studies of host susceptibility and transmission.

• MeSH
• Insect Vectors parasitology   MeSH
• Canaries parasitology   MeSH
• Bird Diseases parasitology   transmission   MeSH
• Simuliidae parasitology   MeSH
• Trypanosoma isolation & purification   MeSH
• Trypanosomiasis transmission   veterinary   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH