Development of two species of the Trypanosoma theileri complex in tabanids

Tabanus chrysurus is a potential biological vector of Trypanosoma (Megatrypanum) theileri in Japan

Several species of horse flies (Diptera: Tabanidae) are known as vectors of Trypanosoma (Megatrypanum) theileri and T. theileri-like trypanosomes; these host-parasite relationships were established based on the developmental stages of these parasites discovered in the hindgut of horse flies. T. theileri and T. theileri-like trypanosomes have been detected in cattle and wild deer in Japan; however, the vector horse fly species remains unidentified. Therefore, in this study, we aimed to identify the potential horse fly species serving as vectors of T. theileri in Japan. A total of 176 horse flies were collected between June to September 2020 and 2021 in Tokachi, Hokkaido, Japan. The T. theileri infection in the captured horse flies was determined by PCR and microscopic analyses of their midgut and hindgut. Additionally, the trypanosome, microscopically detected in a horse fly, was molecularly characterized and phylogenetically analyzed using 18S rRNA and partial cathepsin L-like protein gene (CATL) sequence of the trypanosome. The microscopy and PCR analyses revealed 0.57% and 35.8% prevalence of T. theileri in horse flies, respectively. Epimastigote stages of T. theileri, adhered to the hindgut epithelial cells of Tabanus chrysurus via flagella or actively moving in the lumen of the gut, were detected. Phylogenetic analysis revealed the connection of isolated trypanosomes with T. theileri in the TthI clade. These results suggest that Ta. chrysurus is a potential vector of T. theileri.

Parasites of firebugs in Austria with focus on the "micro"-diversity of the cosmopolitan trypanosomatid Leptomonas pyrrhocoris

In this work, we investigated parasites of the firebug Pyrrhocoris apterus in Austria and demonstrated that in addition to the extensively studied Leptomonas pyrrhocoris, it can also be infected by Blastocrithidia sp. and by a mermithid, which for the first time has been characterized using molecular methods. This diversity can be explained by the gregarious lifestyle, as well as the coprophagous and cannibalistic behavior of the insect hosts that makes them susceptible to various parasites. In addition, we showed no tight association of the L. pyrrhocoris haplotypes and geographical locations (at least, considering the relatively small scale of locations in Austria) implying that the natural populations of L. pyrrhocoris are mixed due to the mobility of their firebug hosts.

An epidemiological survey of vector-borne pathogens infecting cattle in Kyrgyzstan

Cattle production is a major contributor to the national economy of Kyrgyzstan. Most cattle in Kyrgyzstan are managed via extensive systems and graze in communal pastures. As a result, infestations with ectoparasites are widespread, implying that various vector-borne diseases might be common in cattle. However, methods to control such infectious diseases are not available in Kyrgyzstan because the epidemiology of vector-borne pathogens (VBPs) infecting cattle remains unclear. The present study was therefore designed to survey Kyrgyz cattle for VBPs. We prepared blood DNA samples from 319 cattle in Kyrgyzstan and screened them with specific PCR assays for detecting Babesia bovis, Babesia bigemina, Babesia naoakii, Theileria annulata, Theileria orientalis, Trypanosoma evansi, Trypanosoma theileri, and Anaplasma marginale infections. Our findings indicated that the surveyed cattle were infected with six of the eight pathogens targeted, with the exceptions being B. naoakii and Try. evansi. The most common pathogen was T. orientalis (84.3%), followed by B. bigemina (47.6%), T. annulata (16.6%), A. marginale (11.6%), Try. theileri (7.2%), and B. bovis (2.5%). Additional screening of the B. bovis- and B. bigemina-negative samples with a Babesia genus-specific 18S rRNA PCR identified two positive samples, and sequencing analysis confirmed that each of them was infected with either Babesia major or Babesia occultans. To the best of our knowledge, this is the first report of B. bovis, B. bigemina, B. occultans, Try. theileri, and A. marginale infections in cattle in Kyrgyzstan. Our findings suggest that cattle in Kyrgyzstan are at high risk of infectious diseases caused by VBPs.

The Mite Steatonyssus periblepharus Is a Novel Potential Vector of the Bat Parasite Trypanosoma dionisii

Trypanosoma dionisii, for which only bat bugs (Cimicidae) had previously been demonstrated as vectors, was, for the first time, detected in the gamasine mite Steatonyssus periblepharus in Russia. The molecular phylogenetic analysis indicated that trypanosomes found in these mites belong to the "clade A" of T. dionisii, which, based on genetic distances, can be considered as a species separate from the sister clade B, and according to available data also has a distinct geographic distribution. The presence of developmental forms of T. dionisii resembling those previously described during the development of this trypanosome in cimicids suggests that S. periblepharus is a novel vector of the studied trypanosome.

Seasonal Variation and Factors Affecting Trypanosoma theileri Infection in Wild Sika Deer (Ezo Sika Deer Cervus nippon yesoensis) in Eastern Hokkaido

Trypanosoma (Megatrypanum) spp. are isolated from domestic and wild ruminants, including deer, worldwide. The prevalence of trypanosomes in mammals is influenced by a number of factors such as host age and vector abundance. However, the seasonal variation of and factors affecting trypanosome infection in the wild deer population remain elusive. In this study, we analyzed the seasonal variation in trypanosome prevalence and the factors that affect Trypanosoma theileri Laveran, 1902, infection in wild sika deer (Ezo sika deer) Cervus nippon yesoensis (Heude, 1884) in Eastern Hokkaido through a two-year survey. Seasonal variation in the prevalence of trypanosome infection in the deer population ranged from 0 to 41% as per hematocrit concentration and 17 to 89% as per PCR results. In general, the prevalence of T. theileri by PCR in 2020 was higher than that in 2019. Moreover, the prevalence was significantly higher in the aged population than among the younger population. These findings may explain why individual conditions and sampling season were associated with trypanosome prevalence. This is the first study to investigate the seasonal variation in and risk factors affecting trypanosome infection in wild deer.

The Roles of Mosquitoes in the Circulation of Monoxenous Trypanosomatids in Temperate Climates

Monoxenous (insect-restricted) trypanosomatids are highly diverse and abundant in nature. While many papers focus on the taxonomy and distribution of these parasites, studies on their biology are still scarce. In particular, this concerns trypanosomatids inhabiting the ubiquitous mosquitoes. To shed light on the circulation of monoxenous trypanosomatids with the participation of mosquitoes, we performed a multifaceted study combining the examination of naturally- and experimentally-infected insects using light and electron microscopy and molecular identification of parasites. Our examination of overwintering mosquitoes (genera Culex and Culiseta) revealed that their guts contained living trypanosomatids, which can be spread during the next season. Experimental infections with Crithidia spp. demonstrated that imagines represent permissive hosts, while larvae are resistant to these parasites. We argue that for the parasites with wide specificity, mosquitoes act as facultative hosts. Other trypanosomatids may have specific adaptations for vertical transmission in these insects at the expense of their potential to infect a wider range of hosts and, consequently, abundance in nature.