International journal for parasitology最新文献

Two microsporidian species infect honeybees worldwide, Nosema apis and Nosema ceranae. Two different clinical patterns are considered: nosemosis type A (N. apis) and nosemosis type C (N. ceranae). Nosemosis type A is characterized in acute forms and nosemosis type C shows no clear outward clinical signs. The development of a rapid and simple tool for Nosema detection could allow beekeepers or veterinarians to carry out diagnostic tests in situ. Currently, PCR and microscopy are expensive techniques that require qualified staff and may not be available in every laboratory. The present study describes the production and characterization of four monoclonal antibodies (mAbs) against N. ceranae and N. apis, and the development of an IFAT. An IFAT using the mAbs was compared with microscopy and PCR for 180 beehive samples. The diagnostic test revealed similar sensitivity and specificity percentages to IFAT (97.79% and 93.18%, respectively) and microscopy (97.79% and 95.45%), considering 100% for the PCR as the 'gold standard'. A mAb (7D2) was patented for its high specificity for N. ceranae. The IFAT using the mAbs is a good alternative to microscopy and PCR in laboratories where PCR is not available for the detection and identification of both Nosema spp.

Parasites can provide suitable models for studying β-diversity due to their strict dependence on both the environment and the biology and distribution of their hosts, aiding in the interpretation of any patterns that hosts can display. With the aim of quantifying the relative importance of host features, environmental factors and spatial distances as drivers of fish parasite β-diversity along a unidirectional gradient, the structure of fish parasite assemblages was analysed using generalised dissimilarity models (GDMs). A total of 150 poeciliid fish were examined for larval trematodes, recording host features and physical parameters of each sampling site along the stream. Differences among digenean communities increased when Strahler order changed along the stream, associated with increasing species richness and abundance downstream. Environmental gradient, spatial distance and host features were identified as significant determining factors of species turnover, with conductivity being the most important, followed by spatial distance. In the present study, environmental variables were spatially structured along the stream, their effects as structurers of parasite β-diversity being higher than the pure environmental or the pure distance effect. Such predominance prevents us from establishing at what point on the continuum from niche to neutrality these communities are located. Results from the present research contribute to improving our knowledge of the factors that shape parasite community changes, and underline the importance of considering the pure and shared effects of spatial, environmental and host feature factors in order to determine the real contribution of each one as a determinant of parasite β- diversity.

The fast technological advances of molecular tools have enabled us to uncover a new dimension hidden within parasites and their hosts: their microbiomes. Increasingly, parasitologists characterise host microbiome changes in the face of parasitic infections, revealing the potential of these microscopic fast-evolving entities to influence host-parasite interactions. However, most of the changes in host microbiomes seem to depend on the host and parasite species in question. Furthermore, we should understand the relative role of parasitic infections as microbiome modulators when compared with other microbiome-impacting factors (e.g., host size, age, sex). Here, we characterised the microbiome of a single intermediate host species infected by two parasites belonging to different phyla: the acanthocephalan Plagiorhynchus allisonae and a dilepidid cestode, both infecting Transorchestia serrulata amphipods collected simultaneously from the same locality. We used the v4 hypervariable region of the 16S rRNA prokaryotic gene to identify the hemolymph bacterial community of uninfected, acanthocephalan-infected, and cestode-infected amphipods, as well as the bacteria in the amphipods' immediate environment and in the parasites infecting them. Our results show that parasitic infections were more strongly associated with differences in host bacterial community richness than amphipod size, presence of amphipod eggs in female amphipods, and even parasite load. Amphipods infected by acanthocephalans had the most divergent bacterial community, with a marked decrease in alpha diversity compared with cestode-infected and uninfected hosts. In accordance with the species-specific nature of microbiome changes in parasitic infections, we found unique microbial taxa associating with hosts infected by each parasite species, as well as taxa only shared between a parasite species and their infected hosts. However, there were some bacterial taxa detected in all parasitised amphipods (regardless of the parasite species), but not in uninfected amphipods or the environment. We propose that shared bacteria associated with all hosts parasitised by distantly related helminths may be important either in helping host defences or parasites' success, and could thus interact with host-parasite evolution.

Ticks are important medical and veterinary parasites that represent a substantial health threat to humans, companion animals, and livestock. Ixodiphagus wasps (Hymenoptera; Encyrtidae) are known endoparasitoids of ixodid (hard) and argasid (soft) ticks, with potential utility as natural biocontrol agents. Two species, Ixodiphagus brunneus and Ixodiphagus mysorensis, are previously recorded from Australia, however, the genus lacks formal revisionary work in Australia, and the validity and host ranges of these species remain uncertain. This work aimed to investigate the diversity of Ixodiphagus in Australasia and provide a molecular data resource for future work on these understudied endoparasitoids. We extracted DNA from archival Ixodiphagus specimens from Australian and New Zealand insect collections and performed high-throughput sequencing which resulted in complete or mostly complete mitochondrial genome sequences from 11 specimens, including I. brunneus, Ixodiphagus taiaroaensis, and a novel Ixodiphagus sp. reared from Rhipicephalus linnaei from Townsville, Australia. In addition, approximately 70% of the genome of the Wolbachia endosymbiont of I. brunneus was recovered. Finally, we screened 178 recently collected pooled tick samples from southern New South Wales, Australia, for Ixodiphagus spp. using 28S rRNA and cytochrome c oxidase subunit 1(COI) gene PCR, and recovered 14 positive samples. Phylogenetic analysis of Australasian Ixodiphagus spp. based on 28S rRNA and complete mitochondrial genome sequences determined that members of the Australasian fauna are distinct from Ixodiphagus hookeri (the only other Ixodiphagus species for which genetic data exists), and that at least two distinct species are present in Australia; I. brunneus identified from Ixodes holocyclus and Haemaphysalis bancrofti ticks, and an uncharacterised Ixodiphagus sp. found in Rhipicephalus linnaei ticks from northern Queensland. Furthermore, there was substantial genetic diversity at the 28S rRNA loci among I. brunneus samples, which may represent normal genetic variability or a secondary cryptic species. The molecular data generated here represents the first known for the genus Ixodiphagus in Australasia, doubling that of the world fauna, and provides the first known complete mitochondrial genomes for these important tick parasitoids.

Although benefits of selection for host resistance to gastro-intestinal nematodes have long been recognized, its costs on production traits remain unclear. A main difficulty when studying those costs is to disentangle genetic effects due to selection from plastic responses induced by infection. Putative costs of host resistance have been extensively investigated in growing sheep. However, while most of those studies have relied on live weight to assess body growth, more comprehensive assessments accounting for body composition are advocated to detect trade-offs. In this study we used 90 female lambs from lines divergently selected on resistance to Haemonchus contortus that we experimentally infected (n = 60) or not (n = 30) under controlled conditions. As those conditions were defined to enable uninfected lambs to fully express their growth potential, we sought to precisely identify the effects of selection for host resistance on health traits and on growth traits. We assessed muscular and fat growth based on repeated measurements with dorsal ultrasonography for all lambs on farm, and with whole-body computed tomography (CT) scans for a subgroup of 18 infected lambs. Lambs achieved a high growth rate, including infected ones despite their high worm burden (confirmed at necropsy in the subgroup). As expected, lambs from the resistant (R) line were less infected than those from the susceptible (S) line. However, the clear pathogenic effects observed on muscular growth and voluntary feed intake were similar between lines. In contrast, a line difference in body fat was supported both by dorsal and volumetric CT measurements. Specifically, lower fat in the R line compared with the S line was observed equally in infected and uninfected groups, thus providing evidence for a constitutive cost of host resistance. Although this cost is not necessarily disadvantageous in nutrient-rich environments exposing animals to excess fat deposition, its consequences in nutrient-scarce environments may be important to promote sustainable breeding strategies for host resistance.

In the late 1990s, the San Miguel Island fox (Urocyon littoralis littoralis) faced near-extinction. Fourteen of the 15 remaining foxes were placed into an island-based captive breeding program used to repopulate the island. Although the fox population in San Miguel reached pre-decline numbers by 2010, a second decline started around 2014, coincidental with a newly observed acanthocephalan parasite. To identify this introduced acanthocephalan species and determine the pathologic consequences of its infection on the health of foxes, we used an extensive record of island fox necropsies and associated parasite collections. In addition, we used detailed fox capture-recapture data to investigate population health and demographic trends of foxes before and after parasite emergence. We identify the parasite as Pachysentis canicola, a common acanthocephalan in mainland foxes in North America. The parasite was detected in 69% of the necropsied foxes from San Miguel Island and was not found in any of the other five Channel Island fox subspecies. Health impacts attributed to the acanthocephalan parasite, including erosive and ulcerative enteritis, transmural necrosis, and inflammation, were described in 47% of the foxes infected with the acanthocephalan. Despite infection with various other helminth parasite species, body condition remained good and the mortality rate low in San Miguel Island foxes until the arrival of the acanthocephalan. Body condition improved after 2018, perhaps due to increases in rainfall following a drought, but remained 27% lower than the pre-acanthocephalan period, which suggests that environmental conditions and parasitism jointly drive fox population dynamics.

Sulphite oxidase has an essential role in detoxifying environmental and endogenously generated sulphite into sulphate and requires the molybdenum cofactor (Moco) to function. Until recently it was believed that the synthesis pathway for Moco was so important for survival that it was conserved in all multicellular animals. Here we report the use of comparative genomics to identify the absence of the first enzyme involved in Moco synthesis in Haemonchus contortus, a highly pathogenic and economically important helminth of livestock that, similar to many parasitic nematode species, has proved difficult to maintain in vitro. We show that Moco deficiency in Haemonchus leads to a high sensitivity to environmental sulphite and limits the ability to maintain the early parasitic larval stages in vitro. Analogous losses in Moco synthesis in other recently sequenced nematode species are also identified. These findings may lead to improved culture methods for parasitic nematodes and to novel approaches for their control.

Litomosoides includes filarial nematodes capable of infecting various vertebrate species. While Litomosoides has been extensively studied in rodents, research on its association with bats remains limited. The transmission dynamics of this parasite are complex, involving moving between different invertebrate hosts before reaching the final host. Most investigations concerning microfilariae have concentrated on their morphological characteristics, with scant attention paid to ecological aspects, particularly in human-altered landscapes. This study represents the first known documentation of Litomosoides in bats within an urban environment. It investigates their response to urbanization in their interaction with the synanthropic bat Artibeus jamaicensis and its ectoparasites. The objective was to explore the influence of urban landscapes on Litomosoides prevalence in synanthropic hosts. Blood samples were collected along urban-rural gradients, and parasite presence was confirmed through direct observation in blood smears and PCR. Phylogenetic analysis based on the mitochondrial cytochrome c oxidase subunit 1 gene (COX1), which exhibited robust support values, indicates that the microfilaria found in A. jamaicensis is closely related to Litomosoides chandleri. However, it also suggests the possibility of an unidentified, and therefore potentially new, species within the genus Litomosoides. Additionally, Litomosoides DNA was detected in Periglischrus iheringi (Acari: Spinturnicidae) and in the bat fly Trichobius intermedius collected from the bat. The parasite sequences obtained from these three interacting species exhibited a genetic distance as low as 0.002. The highest prevalences were recorded in forested areas (28.6%) compared with urban areas (21.2%). However, within the urban landscape, prevalence varied from 3.8% to 21.2%, being highest in densely built-up areas. Analysis of the urban landscape suggested that the prevalence of Litomosoides in A. jamaicensis is the result of a multifactorial and synergistic process involving ectoparasite load, host abundance, and the extent of impervious surfaces (NDBI).

Submerged aquatic vegetation (macrophytes) can provide prey with refuges from predators and may perform a similar role for interactions with other natural enemies such as parasites. This could occur by interfering with the ability of free-swimming infectious parasite stages to locate or move towards hosts, reducing infections. Alternatively, infections may increase if macrophytes reduce host anti-parasite behaviours such as detection or evasion. Both scenarios could be affected by macrophyte density and structural complexity. Here we investigated whether experimental infection of tadpoles (Rana sylvatica and Rana pipiens) by parasitic flatworms (the trematodes Ribeiroia ondatrae and Echinostoma spp. was affected by the presence of artificial vegetation with varying density and complexity (simple versus branching), as well as tadpole activity under these conditions. Macrophyte presence significantly reduced tadpole infection loads only in the highest density treatment, but there was no effect of structural complexity. Related to this, tadpoles spent significantly more time near aquatic vegetation when it was dense but showed no preference for either structural type. Our results indicate that aquatic vegetation can reduce parasite transmission in certain scenarios, with further studies needed to explore how structural complexity in natural systems can affect host-parasite interactions, considering the massive physical alterations possible through eutrophication and the introduction of invasive plant species.

The Azygiidae Looss, 1899 is a family of digeneans with a Holarctic distribution in which members of some genera mature in marine elasmobranchs while others occur only in freshwater teleosts. Some have questioned whether the marine genus Otodistomum Stafford, 1904 indeed belongs to the same family as the freshwater azygiid genera, namely Azygia Looss, 1899, Proterometra Horsfall, 1933, and Leuceruthrus Marshall and Gilbert, 1905. We present phylogenetic analyses based on mitochondrial genomes, rDNA operons, and partial cytochrome c oxidase I (Cox1) sequences from North American and Asian species that support the monophyly of Azygiidae, and placement of Azygioidea in the suborder Hemiurata, in contrast to recently published mitochondrial genome phylogenies. All phylogenies indicate that Azygia includes Leuceruthrus, which we therefore propose to be a junior synonym, together with suppression of the Leuceruthrinae. The status of Proterometra was equivocal, with support in some but not all analyses of 28S, but not in other markers. We describe a new species of Azygia from northeastern North America. Our results confirm the morphological variability of adults in Azygia, with worm size positively correlated with host size in Azygia angusticauda. Phylogenies suggest a marine origin for the Azygiidae, and a Palearctic origin for freshwater azygiids, with a single trans-Atlantic radiation to the Nearctic.