Diversity and role of cave-dwelling hematophagous insects in pathogen transmission in the Afrotropical region

Tick findings from subterranean environments in the Central German Uplands and Luxembourg reveal a predominance of male Ixodes hexagonus

Questing ticks are usually collected by flagging or dragging. Mostly exophilic tick species are caught, such as Ixodes ricinus, the most common tick in Central Europe. In the present study, ticks collected from underground environments in the Grand Duchy of Luxembourg and in the Central German Uplands (Federal States of Hesse, Bavaria, Thuringia, Baden-Wuerttemberg, Rhineland-Palatinate, Saarland and Northrhine-Westphalia) were investigated. Six tick species were revealed among the 396 analyzed specimens: Ixodes ariadnae, Ixodes canisuga, Ixodes hexagonus, I. ricinus, Ixodes trianguliceps, and Dermacentor marginatus. Adults and immatures of I. hexagonus dominated the findings (57% of all specimens), especially in shelters acting as potential resting places of main hosts. Ixodes canisuga and I. trianguliceps were for the first time recorded in Luxembourg, and one nymph of the bat tick I. ariadnae represents only the second report for Germany. Collecting ticks in subterranean environments turned out to be a useful approach to increase knowledge about the occurrence of relatively rare tick species, including those that spend most of their lifetime on their hosts, but detach in such environmental settings.

Trends in Bacterial Pathogens of Bats: Global Distribution and Knowledge Gaps

Bats have received considerable recent attention for infectious disease research because of their potential to host and transmit viruses, including Ebola, Hendra, Nipah, and multiple coronaviruses. These pathogens are occasionally transmitted from bats to wildlife, livestock, and to humans, directly or through other bridging (intermediate) hosts. Due to their public health relevance, zoonotic viruses are a primary focus of research attention. In contrast, other emerging pathogens of bats, such as bacteria, are vastly understudied despite their ubiquity and diversity. Here, we describe the currently known host ranges and geographic distributional patterns of potentially zoonotic bacterial genera in bats, using published presence-absence data of pathogen occurrence. We identify apparent gaps in our understanding of the distribution of these pathogens on a global scale. The most frequently detected bacterial genera in bats are Bartonella, Leptospira, and Mycoplasma. However, a wide variety of other potentially zoonotic bacterial genera are also occasionally found in bats, such as Anaplasma, Brucella, Borrelia, Coxiella, Ehrlichia, Francisella, Neorickettsia, and Rickettsia. The bat families Phyllostomidae, Vespertilionidae, and Pteropodidae are most frequently reported as hosts of bacterial pathogens; however, the presence of at least one bacterial genus was confirmed in all 15 bat families tested. On a spatial scale, molecular diagnostics of samples from 58 countries and four overseas departments and island states (French Guiana, Mayotte, New Caledonia, and Réunion Island) reported testing for at least one bacterial pathogen in bats. We also identified geographical areas that have been mostly neglected during bacterial pathogen research in bats, such as the Afrotropical region and Southern Asia. Current knowledge on the distribution of potentially zoonotic bacterial genera in bats is strongly biased by research effort towards certain taxonomic groups and geographic regions. Identifying these biases can guide future surveillance efforts, contributing to a better understanding of the ecoepidemiology of zoonotic pathogens in bats.

Bat Flies and Their Microparasites: Current Knowledge and Distribution

Bats are the second most diverse mammalian group, playing keystone roles in ecosystems but also act as reservoir hosts for numerous pathogens. Due to their colonial habits which implies close contacts between individuals, bats are often parasitized by multiple species of micro- and macroparasites. The particular ecology, behavior, and environment of bat species may shape patterns of intra- and interspecific pathogen transmission, as well as the presence of specific vectorial organisms. This review synthetizes information on a multi-level parasitic system: bats, bat flies and their microparasites. Bat flies (Diptera: Nycteribiidae and Streblidae) are obligate, hematophagous ectoparasites of bats consisting of ~500 described species. Diverse parasitic organisms have been detected in bat flies including bacteria, blood parasites, fungi, and viruses, which suggest their vectorial potential. We discuss the ecological epidemiology of microparasites, their potential physiological effects on both bats and bat flies, and potential research perspectives in the domain of bat pathogens. For simplicity, we use the term microparasite throughout this review, yet it remains unclear whether some bacteria are parasites or symbionts of their bat fly hosts.

DNA-aided identification of Culex mosquitoes (Diptera: Culicidae) reveals unexpected diversity in underground cavities in Austria

Subterranean cavities serve as resting places and hibernation shelters for mosquitoes. In Europe, members of the genus Culex are often the most abundant insects on cave walls. Culex pipiens L., the common house mosquito, exists in two physically very similar, yet genetically and ecologically distinct biotypes (or forms, 'f.'), namely Cx. pipiens f. pipiens and Cx. pipiens f. molestus. Autogeny and stenogamy of the latter form have been interpreted as adaptations to underground habitats. The epigean occurrence of the two biotypes and their hybrids was recently examined in Eastern Austria, but the hypogean distribution of the Cx. pipiens complex and morphologically similar non-members such as Cx. torrentium is unknown. Considering the key role of Culex mosquitoes in the epidemiology of certain zoonotic pathogens, the general paucity of data on species composition and relative abundance in subterranean shelters appears unfortunate.For a first pertinent investigation in Austria, we collected mosquitoes in four eastern federal states. Based on analyses of the ACE2 gene and the CQ11 microsatellite locus, 150 female and three male mosquitoes of the genus Culex, two females of the genus Culiseta and a single female of the genus Anopheles were determined to species level or below. In our catches, Cx. pipiens f. pipiens exceeded the apparent abundance of the purportedly cave-adapted Cx. pipiens f. molestus many times over. Records of Cx. hortensis and Cx. territans, two species rarely collected in Austria, lead us to infer that underground habitats host a higher diversity of culicine mosquitoes than previously thought.

Trypanosoma madeirae sp. n.: A species of the clade T. cruzi associated with the neotropical common vampire bat Desmodus rotundus

Molecular phylogenetic studies have revealed the growing diversity of bat trypanosomes. Here, 14 isolates from blood samples of the vampire bat Desmodus rotundus (Phyllostomidae) from Rio de Janeiro, Southeast Brazil, were cultivated, and morphologically and molecularly characterized. All isolates represent a novel species named Trypanosoma madeirae n. sp. positioned in the Neobat lineage of the clade T. cruzi. The Neobat lineage also comprises closely related trypanosomes of clades Neotropic 1, 2 and 3 from diverse phyllostomid species. Trypanosomes of Neotropic 1, found in Trachops cirrhosus and Artibeus jamaicensis (phyllostomids), likely represent a different species or genotype closely related to T. madeirae. Consistent with its phylogenetic positioning, T. madeirae differs from Trypanosoma cruzi in morphology of both epimastigote and trypomastigote culture forms and does not infect Triatoma infestans. Similar to its closest relatives of Neobat lineage, T. madeirae was unable to develop within mammalian cells. To date, PCR-surveys on archived blood/liver samples unveiled T. madeirae exclusively in D. rotundus from Southern to Northern Brazil. The description of a new species of bat trypanosome associated with vampire bats increases the repertoire of trypanosomes infecting D. rotundus, currently comprised of Trypanosoma cruzi, T. cruzi marinkellei, Trypanosoma dionisii, Trypanosoma rangeli, Trypanosoma pessoai, and Trypanosoma madeirae.

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Trypanosoma madeirae n. sp. was so far only detected in the vampire bat Desmodus rotundus.

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T. madeirae clustered with other Neotropical trypanosomes in the Neobat lineage of the clade T. cruzi.

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Several species of trypanosomes are hosted by Desmodus rotundus.

Ebola Virus Maintenance: If Not (Only) Bats, What Else?

The maintenance mechanisms of ebolaviruses in African forest ecosystems are still unknown, but indirect evidences point at the involvement of some bat species. Despite intense research, the main bat-maintenance hypothesis has not been confirmed yet. The alternative hypotheses of a non-bat maintenance host or a maintenance community including, or not, several bat and other species, deserves more investigation. However, African forest ecosystems host a large biodiversity and abound in potential maintenance hosts. How does one puzzle out? Since recent studies have revealed that several bat species have been exposed to ebolaviruses, the common denominator to these hypotheses is that within the epidemiological cycle, some bats species must be exposed to the viruses and infected by these potential alternative hosts. Under this constraint, and given the peculiar ecology of bats (roosting behaviour, habitat utilisation, and flight mode), we review the hosts and transmission pathways that can lead to bat exposure and infection to ebolaviruses. In contrast to the capacity of bats to transmit ebolaviruses and other pathogens to many hosts, our results indicate that only a limited number of hosts and pathways can lead to the transmission of ebolaviruses to bats, and that the alternative maintenance host, if it exists, must be amongst them. A list of these pathways is provided, along with protocols to prioritise and investigate these alternative hypotheses. In conclusion, taking into account the ecology of bats and their known involvement in ebolaviruses ecology drastically reduces the list of potential alternative maintenance hosts for ebolaviruses. Understanding the natural history of ebolaviruses is a health priority, and investigating these alternative hypotheses could complete the current effort focused on the role of bats.

Diversity Of Mosquito Species Ovipositing In Different Zones of Light Intensity Within Limestone Caves In Thailand

Climate change and human activity affect the geographical and annual distribution and population abundance of mosquitoes. As natural habitats are reduced, it is hypothesized that mosquitoes may seek refuge in more stable environments such as cave habitats. Therefore, we explored the species diversity of mosquitoes exploiting cave habitats in Thailand. Ten species belonging to 4 genera were collected, of which none were considered to be true cave-dwelling species (Troglobiont). The known cavernicolous species, Aedes cavaticus, was observed to oviposit outside of the cave and therefore should be categorized as a subtroglophilic species. Other species were also oviposited inside the cave but should be regarded as trogloxenic species. There was no clear association between environmental factors and mosquito abundance inside the 4 limestone caves, except for Ae. cavaticus, which was positively correlated with rainfall. This study indicates that different biotic or abiotic factors may be involved in mosquito oviposition site selection inside caves.

Trypanosoma rangeli is phylogenetically closer to Old World trypanosomes than to Trypanosoma cruzi

Trypanosoma rangeli and Trypanosoma cruzi are generalist trypanosomes sharing a wide range of mammalian hosts; they are transmitted by triatomine bugs, and are the only trypanosomes infecting humans in the Neotropics. Their origins, phylogenetic relationships, and emergence as human parasites have long been subjects of interest. In the present study, taxon-rich analyses (20 trypanosome species from bats and terrestrial mammals) using ssrRNA, glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH), heat shock protein-70 (HSP70) and Spliced Leader RNA sequences, and multilocus phylogenetic analyses using 11 single copy genes from 15 selected trypanosomes, provide increased resolution of relationships between species and clades, strongly supporting two main sister lineages: lineage Schizotrypanum, comprising T. cruzi and bat-restricted trypanosomes, and Tra[Tve-Tco] formed by T. rangeli, Trypanosoma vespertilionis and Trypanosoma conorhini clades. Tve comprises European T. vespertilionis and African T. vespertilionis-like of bats and bat cimicids characterised in the present study and Trypanosoma sp. Hoch reported in monkeys and herein detected in bats. Tco included the triatomine-transmitted tropicopolitan T. conorhini from rats and the African NanDoum1 trypanosome of civet (carnivore). Consistent with their very close relationships, Tra[Tve-Tco] species shared highly similar Spliced Leader RNA structures that were highly divergent from those of Schizotrypanum. In a plausible evolutionary scenario, a bat trypanosome transmitted by cimicids gave origin to the deeply rooted Tra[Tve-Tco] and Schizotrypanum lineages, and bat trypanosomes of diverse genetic backgrounds jumped to new hosts. A long and independent evolutionary history of T. rangeli more related to Old World trypanosomes from bats, rats, monkeys and civets than to Schizotrypanum spp., and the adaptation of these distantly related trypanosomes to different niches of shared mammals and vectors, is consistent with the marked differences in transmission routes, life-cycles and host-parasite interactions, resulting in T. cruzi (but not T. rangeli) being pathogenic to humans.