Nematode spicules play a vital role in the reproductive activity of species that possess them. Our primary objective was to compare the lengths of spicules of the laboratory mouse (Mus musculus) – maintained isolate H. bakeri – with those of H. polygyrus from naturally infected wood mice (Apodemus sylvaticus). On a more limited scale, we also included H. glareoli from bank voles (Myodes glareolus), a species reputed to possess longer spicules than either of the 2 former species. In total, we measured 1264 spicules (H. bakeri, n = 614; H. polygyrus n = 582; and H. glareoli, n = 68). There was a highly significant difference between the spicule lengths of the Nottingham-maintained H. bakeri (mean = 0.518 mm) and H. polygyrus (0.598 mm) from 11 different localities across the British Isles. A comparison of the spicules of H. bakeri maintained in 4 different laboratories in 3 continents revealed a range in the mean values from 0.518 to 0.540 mm, while those of worms from Australian wild house mice were shorter (0.480 mm). Mean values for H. polygyrus from wood mice from the British Isles ranged from 0.564 to 0.635 mm, although isolates of this species from Norway had longer spicules (0.670 mm). In agreement with the literature, the spicules of H. glareoli were considerably longer (1.098 mm). Since spicules play a vital role in the reproduction of nematode species that possess them, the difference in spicule lengths between H. bakeri and H. polygyrus adds to the growing evidence that these 2 are quite distinct species and likely reproductively isolated.

In recent field studies, suspected gymnophallid metacercariae were histologically located in the mantle of mussels from the Norwegian Sea. Mussels from the sites in which that infection was detected also presented abnormally high pearl numbers. It has been previously described that gymnophallid metacercariae could cause pearl formation processes in mussels, as a host reaction to encapsulate these metacercariae. Given the pathological host reaction these parasites elicit, a study was performed to identify gymnophallid metacercariae found in mussels collected from Tromsø at morphological and molecular level and to assess, by the use of molecular tools, the relationship between the parasite and the biological material inside the pearls. As a result, Gymnophallus bursicola metacercariae infecting Norwegian Mytilus edulis were identified according to morphological characters, along with the first 18S rDNA and COI sequences for this trematode species. In addition, parasite DNA from the core of the pearls was extracted and amplified for the first time, confirming the parasitological origin of these pearls. This procedure could allow identifying different parasitic organisms responsible for the generation of pearls in bivalves.

Individual hosts are often co-infected with multiple parasite species. Evidence from theoretical and empirical studies supports the idea that co-occurring parasites can impact each other and their hosts via synergistic or antagonistic interactions. The fundamental aim of understanding the consequences of co-infection to hosts and parasites requires an understanding of patterns of species co-occurrence within samples of hosts. We censused parasite assemblages in 755 adult, male fathead minnows collected from 7 lakes/ponds in southern Alberta, Canada between 2018 and 2020. Fifteen species of endoparasites infected fathead minnows, 98% of which were co-infected with between 2 and 9 parasite species (mean species richness: 4.4 ± 1.4). Non-random pairwise associations were detected within the overall parasite community. There were particularly strong, positive associations in the occurrences and intensities of the 2 congeneric larval trematodes Ornithodiplostomum sp. and Ornithodiplostomum ptychocheilus that comprised >96% of the 100 000+ parasites counted in the total sample of minnows. Furthermore, the occurrence of Ornithodiplostomum sp. was a strong predictor of the occurrence of O. ptychocheilus, and vice versa. Positive covariation in the intensities of these 2 dominants likely arises from their shared use of physid snails as first intermediate hosts in these waterbodies. These 2 species represent a predictable and non-random component within the complex assemblage of parasites of fathead minnows in this region.

Combining the biogeography and phylogenetic patterns of parasite-host associations allows a better understanding of the history of parasite–host interactions, which can be achieved via biogeographic regionalization incorporating phylogenetic information. Recently, the concepts of evoregions (regions where a majority of species evolved from one or several ancestors inhabiting these regions) and evolutionary transition zones (regions of high phylogenetic turnover) have been proposed, coupled with a classification approach for these concepts. We applied this approach to 206 flea species and 265 host species of the Palearctic and aimed to identify evoregions and evolutionary transition zones for both fleas and hosts and to understand whether these evoregions and transition zones match each other. We identified 5 evoregions with 3 transition zones for either fleas or hosts, but neither the positions and boundaries of the flea and host evoregions nor the transition zones coincided. Indications of multiple geographic centres of diversification of the same flea lineages suggested that (a) the common evolutionary history of fleas and hosts was characterized by multiple events other than codiversification and that (b) dispersal played an important role in flea and host assemblies. Barriers to dispersal could be represented by landscape features (deserts and mountain ranges) and/or climate differences.

The factors that influence parasite associated bacterial microbial diversity and the geographic distributions of bacteria are not fully understood. In an effort to gain a deeper understanding of the relationship between the bacterial diversity of Ctenocephalides fleas and host species and the external environment, we conducted a metagenetic analysis of 107 flea samples collected from 8 distinct sampling sites in South Africa. Pooled DNA samples mostly comprising of 2 or 3 individuals sampled from the same host, and belonging to the same genetic cluster, were sequenced using the Ion PGM™ Hi-Q™ Kit and the Ion 316™ Chip v2. Differences were detected in the microbiome compositions between Ctenocephalides felis, Ctenocephalides canis and Ctenocephalides connatus. Although based on a small sample, C. connatus occurring on wildlife harboured a higher bacterial richness when compared to C. felis on domestic animals. Intraspecific differences in the microbial OTU diversity were detected within C. f. felis that occurred on domestic cats and dogs. Different genetic lineages of C. f. felis were similar in microbial compositions but some differences exist in the presence or absence of rare bacteria. Rickettsia and Bartonella OTU's identified in South African cat fleas differ from those identified in the USA and Australia. Intraspecific microbial compositions also differ across geographic sampling sites. Generalized dissimilarity modelling showed that temperature and humidity are potentially important environmental factors explaining the pattern obtained.

From the safety inside vehicles, Knowsley Safari offers visitors a close-up encounter with captive olive baboons. As exiting vehicles may be contaminated with baboon stool, a comprehensive coprological inspection was conducted to address public health concerns. Baboon stools were obtained from vehicles, and sleeping areas, inclusive of video analysis of baboon–vehicle interactions. A purposely selected 4-day sampling period enabled comparative inspections of 2662 vehicles, with a total of 669 baboon stools examined (371 from vehicles and 298 from sleeping areas). As informed by our pilot study, front-line diagnostic methods were: QUIK-CHEK rapid diagnostic test (RDT) (Giardia and Cryptosporidium), Kato–Katz coproscopy (Trichuris) and charcoal culture (Strongyloides). Some 13.9% of vehicles were contaminated with baboon stool. Prevalence of giardiasis was 37.4% while cryptosporidiosis was <0.01%, however, an absence of faecal cysts by quality control coproscopy, alongside lower than the expected levels of Giardia-specific DNA, judged RDT results as misleading, grossly overestimating prevalence. Prevalence of trichuriasis was 48.0% and strongyloidiasis was 13.7%, a first report of Strongyloides fuelleborni in UK. We advise regular blanket administration(s) of anthelminthics to the colony, exploring pour-on formulations, thereafter, smaller-scale indicator surveys would be adequate.

The distribution of avian haemosporidians of the genus Leucocytozoon in the Neotropics remains poorly understood. Recent studies confirmed their presence in the region using molecular techniques alone, but evidence for gametocytes and data on putative competent hosts for Leucocytozoon are still lacking outside highland areas. We combined morphological and molecular data to characterize a new Leucocytozoon species infecting a non-migratory red-legged seriema (Cariama cristata), the first report of a competent host for Leucocytozoon in Brazil. Leucocytozoon cariamae n. sp. is distinguished from the Leucocytozoon fringillinarum group by its microgametocytes that are not strongly appressed to the host cell nucleus. The bird studied was coinfected with Haemoproteus pulcher, and we present a Bayesian phylogenetic analysis based on nearly complete mitochondrial genomes of these 2 parasites. Leucocytozoon cariamae n. sp. morphology is consistent with our phylogenetic analysis indicating that it does not share a recent common ancestor with the L. fringillinarum group. Haemoproteus pulcher and Haemoproteus catharti form a monophyletic group with Haemocystidium parasites of Reptilia, supporting the polyphyly of the genus Haemoproteus. We also discussed the hypothesis that H. pulcher and H. catharti may be avian Haemocystidium, highlighting the need to study non-passerine parasites to untangle the systematics of Haemosporida.

The rat lungworm Angiostrongylus cantonensis is a metastrongyloid nematode that causes neurological disorders in its accidental hosts, including humans. This invasive pathogen is native to Southeast Asia and adjacent regions and is gradually expanding its distribution to tropical and subtropical areas with new foci discovered near temperate regions. The parasite has a complex life cycle with a range of gastropods serving as intermediate hosts. A broad spectrum of poikilotherm vertebrates and invertebrates can serve as paratenic hosts. Since it has already been demonstrated that other, non-zoonotic metastrongyloids can survive in their intermediate hosts during the winter, the aim of our study was to evaluate the survival of A. cantonensis third-stage larvae in experimentally infected slugs (Limax maximus) kept at 4.5–7°C for 60 days. Third-stage larvae of A. cantonensis survived the period of low temperature and remained capable of infecting definitive hosts (laboratory rats) afterwards, even though their numbers dropped significantly. These results suggest that further spread to higher latitudes or altitudes is possible in areas with sufficient abundance of definitive hosts, since low winter temperatures are not necessarily an obstacle to the spread of the parasite.

Ticks transmit pathogens and harbour non-pathogenic, vertically transmitted intracellular bacteria termed endosymbionts. Almost all ticks studied to date contain 1 or more of Coxiella, Francisella, Rickettsia or Candidatus Midichloria mitochondrii endosymbionts, indicative of their importance to tick physiology. Genomic and experimental data suggest that endosymbionts promote tick development and reproductive success. Here, we review the limited information currently available on the potential roles endosymbionts play in enhancing tick metabolism and fitness. Future studies that expand on these findings are needed to better understand endosymbionts’ contributions to tick biology. This knowledge could potentially be applied to design novel strategies that target endosymbiont function to control the spread of ticks and pathogens they vector.

Lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in domestic and wild ungulates. This study investigates the distribution, morphology and genetic diversity of D. cervi and a new lungworm species, Dictyocaulus skrjabini n. sp. infecting red deer Cervus elaphus, fallow deer Dama dama and moose Alces alces in Poland and Sweden. The study was conducted on 167 red deer from Poland and on the DNA of lungworms derived from 7 fallow deer, 4 red deer and 2 moose collected in Sweden. The prevalence of D. cervi and D. skrjabini n. sp. in dissected red deer in Poland was 31.1% and 7.2%, respectively. Moreover, D. skrjabini n. sp. was confirmed molecularly in 7 isolates of fallow deer lungworms and 1 isolate of red deer lungworms from Sweden. Dictyocaulus skrjabini n. sp. was established based on combination of their distinct molecular and morphological features; these included the length of cephalic vesicle, buccal capsule (BC), buccal capsule wall (BCW), distance from anterior extremity to the nerve ring, the width of head, oesophagus, cephalic vesicle, BC and BCW, as well as the dimensions of reproductive organs of male and female. Additionally, molecular analyses revealed 0.9% nucleotide sequence divergence for 1,605 bp SSU rDNA, and 16.5–17.3% nucleotide sequence divergence for 642 bp mitochondrial cytB between D. skrjabini n. sp. and D. cervi, respectively, and 18.7–19% between D. skrjabini n. sp. and D. eckerti, which translates into 18.2–18.7% amino acid sequence divergence between D. skrjabini n. sp. and both lungworms.

Invertebrate host–parasite associations are one of the keystones in order to understand vector-borne diseases. The study of these specific interactions provides information not only about how the vector is affected by the parasite at the gene-expression level, but might also reveal mosquito strategies for blocking the transmission of the parasites. A very well-known vector for human malaria is Anopheles gambiae. This mosquito species has been the main focus for genomics studies determining essential key genes and pathways over the course of a malaria infection. However, to-date there is an important knowledge gap concerning other non-mammophilic mosquito species, for example some species from the Culex genera which may transmit avian malaria but also zoonotic pathogens such as West Nile virus. From an evolutionary perspective, these 2 mosquito genera diverged 170 million years ago, hence allowing studies in both species determining evolutionary conserved genes essential during malaria infections, which in turn might help to find key genes for blocking malaria cycle inside the mosquito. Here, we extensively review the current knowledge on key genes and pathways expressed in Anopheles over the course of malaria infections and highlight the importance of conducting genomic investigations for detecting pathways in Culex mosquitoes linked to infection of avian malaria. By pooling this information, we underline the need to increase genomic studies in mosquito–parasite associations, such as the one in Culex–Plasmodium, that can provide a better understanding of the infection dynamics in wildlife and reduce the negative impact on ecosystems.

The mere presence of predators or parasites can negatively impact the fitness of prey or hosts. Exposure to predators during an organism's development can have deleterious effects on juvenile survival and the subsequent adult stage. Currently, it is unknown if parasites have analogous impacts on host larval stages and whether these effects carry over into other subsequent life stages. However, parasites may be exerting widespread yet underestimated non-consumptive effects (NCEs). We tested if Drosophila nigrospiracula larvae avoid pupating near mite cues (caged Macrocheles subbadius) in arena experiments, and measured the rate of pupation in arenas with mites and arenas without mites. Larvae disproportionately pupated on the side of arenas that lacked mite cues. Furthermore, fewer larvae successfully pupated in arenas containing mites cues compared to arenas without mite cues. We found that ectoparasitic mites exert NCEs on Drosophila larvae, even though the larval stage is not susceptible to infection. We discuss these results in the context of parasite impacts on host population growth in an infectious world.

Perkinsus olseni is an industrially significant protozoan parasite of Manila clam, Ruditapes philippinarum. So far, various media, based on Dulbecco's Modified Eagle Medium and Ham's F-12 nutrient mixture with supplementation of fetal bovine serum (FBS), have been developed to proliferate the parasitizing trophozoite stage of P. olseni. The present study showed that P. olseni did not proliferate in FBS-deficient Perkinsus broth medium (PBMΔF), but proliferated well in PBMΔF supplemented with tissue extract of host Manila clams, indicating that FBS and Manila clam tissue contained molecule(s) required for P. olseni proliferation. Preliminary characterization suggested that the host-derived molecule(s) was a heat-stable molecule(s) with a molecular weight of less than 3 kDa, and finally a single molecule required for the proliferation was purified by high-performance liquid chromatography processes. High-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance analyses identified this molecule as glycine betaine (=trimethylglycine), and the requirement of this molecule for P. olsseni proliferation was confirmed by an assay using chemically synthesized, standard glycine betaine. Although glycine betaine was required for the proliferation of all examined Perkinsus species, supplementation of glycine betaine precursors, such as choline and betaine aldehyde, enhanced the proliferation of 4 Perkinsus species (P. marinus, P. chesapeaki, P. mediterraneus and P. honshuensis), but not of 2 others (P. olseni and P. beihaiensis). Thus, it was concluded that the ability to biosynthesise glycine betaine from its precursors varied among Perkinsus species, and that P. olseni and P. beihaiensis lack the ability required to biosynthesize glycine betaine for proliferation.

Leishmaniases affect 12 million people worldwide. They are caused by Leishmania spp., protozoan parasites transmitted to mammals by female phlebotomine flies. During the life cycle, promastigote forms of the parasite live in the gut of infected sandflies and convert into amastigotes inside the vertebrate macrophages. The parasite evades macrophage's microbicidal responses due to virulence factors that affect parasite phagocytosis, survival and/or proliferation. The interaction between Leishmania and macrophage molecules is essential to phagocytosis and parasite survival. Proteins containing leucine-rich repeats (LRRs) are common in several organisms, and these motifs are usually involved in protein–protein interactions. We have identified the LRR17 gene, which encodes a protein with 6 LRR domains, in the genomes of several Leishmania species. We show here that promastigotes of Leishmania (L.) amazonensis overexpressing LaLRR17 are more infective in vitro. We produced recombinant LaLRR17 protein and identified macrophage 78 kDa glucose-regulated protein (GRP78) as a ligand for LaLRR17 employing affinity chromatography followed by mass spectrometry. We showed that GRP78 binds to LaLRR17 and that its blocking precludes the increase of infection conferred by LaLRR17. Our results are the first to report LRR17 gene and protein, and we hope they stimulate further studies on how this protein increases phagocytosis of Leishmania.

Few studies have investigated the ecological interactions between wild species of Suidae and their parasites, leaving our knowledge concerning this host–parasite system fragmented. In the present study, we applied network studies to analyse community nestedness in helminth assemblages of common warthogs, Phacochoerus africanus (Gmelin) (Suidae). Helminth data were compiled from 95 warthogs, including young and adult males and females, from 2 different conservation areas in Mpumalanga and Limpopo Provinces, South Africa, collected monthly over a period of 1 year each. The aim was to study the effect of host sex, age and season of sampling on the structure of helminth infracommunities harboured by the warthogs and to search for non-random structural patterns in the warthog–helminth interaction networks. Furthermore, we investigated the influence of a warthog's age, sex and season of sampling on beta diversity and dark diversity of their helminth infracommunities. Lastly, we asked whether the effects of host sex, age and sampling season on helminth communities differed between the 2 localities. We found that helminth communities of warthogs were nested and host–parasite interactions were influenced by all 3 factors as well as combinations thereof. However, the resulting patterns differed at the 2 localities, indicating that local environmental processes are important drivers of community structure.

Hyalomma marginatum is an important tick species which is the main vector of Crimean–Congo haemorrhagic fever and spotted fever. The species is predominantly distributed in parts of southern Europe, North Africa and West Asia. However, due to ongoing climate change and increasing reports of H. marginatum in central and northern Europe, the expansion of this range poses a potential future risk. In this study, an ecological niche modelling approach to model the current and future climatic suitability of H. marginatum was followed. Using high-resolution climatic variables from the Chelsa dataset and an updated list of locations for H. marginatum, ecological niche models were constructed under current environmental conditions using MaxEnt for both current conditions and future projections under the ssp370 and ssp585 scenarios. Models show that the climatically suitable region for H. marginatum matches the current distributional area in the Mediterranean basin and West Asia. When applied to future projections, the models suggest a considerable expansion of H. marginatum's range in the north in Europe as a result of rising temperatures. However, a decline in central Anatolia is also predicted, potentially due to the exacerbation of drought conditions in that region.

Four methods were compared for the diagnosis of human taeniasis caused by Taenia solium. Fecal samples from persons living in a T. solium endemic region of Madagascar were examined for taeniid eggs by the Kato–Katz method. Subsequently, samples positive (n = 16) and negative (n = 200) for T. solium eggs were examined by (i) amplification of the fragment of small subunit of the mitochondrial ribosomal RNA (rrnS) gene using conventional polymerase chain reaction (PCR) and (ii) a nested PCR of a fragment of the T. solium Tso31 gene. Additionally, 12 egg-positive and all egg-negative samples were tested for coproantigen detection. A further 9 egg-positive fecal samples were examined using both PCRs. Of the 12 egg-positive samples tested by PCRs and coproantigen methods, 9 (75%) were positive by rrnS PCR, 3 (25%) using Tso31-nested PCR and 9 (75%) by coproantigen testing. None of the 200 egg-negative fecal samples was positive in either rrnS or Tso31-nested PCR. Twenty of the 25 egg-positive samples (80%) were positive in rrnS PCR, and DNA sequencing of PCR amplicons was obtained from 18 samples, all confirmed to be T. solium. Twelve of the 25 egg-positive samples (48%) were positive in the Tso31-nested PCR, all of which were also positive by rrnS PCR. It is suggested that species-specific diagnosis of T. solium taeniasis may be achieved by either coprological examination to detect eggs or coproantigen testing, followed by rrnS PCR and DNA sequencing to confirm the tapeworm species in egg-positive or coproantigen-positive samples.

The parasitic nematode Paracapillaria (Ophidiocapillaria) najae De, 1998, found in the Indian cobra Naja naja is redescribed and re-illustrated in the present study. The monocled cobra Naja kaouthia was discovered to be a new host for this parasite in central Thailand. A comprehensive description extending the morphological and molecular characteristics of the parasites is provided to aid species recognition in future studies. The morphometric characters of 41 parasites collected from 5 cobra specimens are compared with those described in the original studies. Phylogenetic analyses using mitochondrial cytochrome c oxidase subunit 1 and nuclear 18S ribosomal RNA genes were performed to provide novel information on the systematics of P. najae. Similar characteristics were observed in the examined nematode samples, despite being found in different hosts, confirming their identity as P. najae. The molecular genetic results support the species status of P. najae, indicating P. najae is well defined and separated from other related nematode species in the family Capillariidae. Morphological descriptions, genetic sequences, evolutionary relationships among capillariids and new host and distribution records of P. najae are discussed. Paracapillaria najae specimens found in the Thai cobra had some morphological variation, and sexual size dimorphism was also indicated. Paracapillaria najae was found to infect various cobra host species and appeared to be common throughout the Oriental regions, consistent with its hosts' distribution.

Many organisms live in fragmented populations, which has profound consequences on the dynamics of associated parasites. Metapopulation theory offers a canonical framework for predicting the effects of fragmentation on spatiotemporal host–parasite dynamics. However, empirical studies of parasites in classical metapopulations remain rare, particularly for vector-borne parasites. Here, we quantify spatiotemporal patterns and possible drivers of infection probability for several ectoparasites (fleas, Ixodes trianguliceps and Ixodes ricinus) and vector-borne microparasites (Babesia microti, Bartonella spp., Hepatozoon spp.) in a classically functioning metapopulation of water vole hosts. Results suggest that the relative importance of vector or host dynamics on microparasite infection probabilities is related to parasite life-histories. Bartonella, a microparasite with a fast life-history, was positively associated with both host and vector abundances at several spatial and temporal scales. In contrast, B. microti, a tick-borne parasite with a slow life-history, was only associated with vector dynamics. Further, we provide evidence that life-history shaped parasite dynamics, including occupancy and colonization rates, in the metapopulation. Lastly, our findings were consistent with the hypothesis that landscape connectivity was determined by distance-based dispersal of the focal hosts. We provide essential empirical evidence that contributes to the development of a comprehensive theory of metapopulation processes of vector-borne parasites.