Parasites can significantly influence the ecology, behaviour and physiology of their hosts sometimes with remarkable effects on their survivorship. However, endemic parasites or those not associated with obvious clinical disease have been partly neglected in the past decades comparatively to the most pathogenic ones. Apicomplexa are an important example of blood parasites that have been broadly investigated, although it can be difficult to determine the effects of infections at the population level, especially in widespread species. Such is the case of the common wall lizard (Podarcis muralis). We investigated 61 populations across Italy between 2008 and 2017 and recorded snout–vent length, latitude, date of collection and took blood samples for parasite count. We modelled parasite prevalence and load in a Bayesian framework. Parasites were present in all populations but 1 and in 13 of them all individuals were parasitized. We recorded almost identical responses for probability of infection and parasite load in both sexes, directly proportional to body size and inversely proportional to latitude, with a peak in cooler months. Therefore, haemosporidians can be very common in P. muralis, although their presence can vary significantly. Moreover, such a high prevalence makes it necessary to investigate to what extent haemosporidians affect hosts' survivorship, taking into consideration abiotic and biotic factors such as temperature, hormone levels and immune response.

Given the importance of angiostrongyliasis as an emerging infectious disease of humans, companion animals, and wildlife, the current study focused on the transmission dynamics of first- and third-stage larvae of the parasitic nematode, Angiostrongylus cantonensis. The migration of infective larvae and their subsequent distribution within the Lymnaeidae snail, Bullastra lessoni, were investigated over time using microscopic examination of histological sections and fresh tissue. Snails were divided into four anatomical regions: (i) anterior and (ii) posterior cephalopedal masses, (iii) mantle skirt and (iv) visceral mass. The viability of free-swimming third-stage larvae, after their release from snail tissues, was evaluated in vitro by propidium iodide staining and infectivity by in vivo infection of Wistar rats. Snails were sequentially dissected over time to assess the number and anatomical distribution of larvae within each snail and hence infer their migration pathway. Herein, ongoing larval migratory activity was detected over 28 days post-infection. A comparison of infection rates and the larval distribution within the four designated snail regions demonstrated a significant relationship between anatomical region and density of infective larvae, with larvae mostly distributed in the anterior cephalopedal mass (43.6 ± 10.8%) and the mantle skirt (33.0 ± 8.8%). Propidium iodide staining showed that free-swimming third-stage larvae retained viability for between 4 and 8 weeks when stored under laboratory conditions. In contrast to viability, larval infectivity in rats remained for up to 2 weeks only. Knowledge gained from the current work could provide information on the development of new approaches to controlling the transmission of this parasite.

In the Anisakidae family, there are nematodes, most of which are parasitic for important commercial fish species. Both public health risks and socio-economic problems are attributed to these parasites. Despite these concerns, knowledge of the metabolism of these parasites remains unknown. Therefore, the main objective of this study was to investigate the receptors of drugs and oxidative metabolic status of two Anisakidae species, Pseudoterranova decipiens (s. s.) and Contracaecum osculatum (s. s.), under the influence of anthelminthic drugs, ivermectin (IVM) and pyrantel (PYR), at different concentrations: 1.56, 3.125 and 6.25 μg mL−1 of culture medium for 3, 6, 9, 12 and 72 h. The mRNA expressions of the γ-aminobutyric acid receptor, acetylcholine receptor subunits, adenosine triphosphate-binding cassette transporters and antioxidative enzymes were determined. The total antioxidant capacity and glutathione S-transferase activity were also examined. To the best of the authors' knowledge, this is the first time that IVM and PYR have been tested against these parasitic nematodes.

Increases in bed net coverage and antimalarial treatment have reduced the risk of malaria in sub-Saharan Africa. However, the pace of reduction has slowed, and new tools are needed to reverse this trend. We evaluated houses screened with insecticide-treated ceiling nets using a cluster randomized-controlled trial in western Kenya. The primary endpoints were Plasmodium falciparum PCR-positive prevalence (PCRPfPR) of children from 7 months to 10 years old and anopheline density. Ceiling nets and bed nets were provided to 1073 houses, and 1162 houses were provided with bed nets only. The treatment and control arms each had four clusters. We conducted three epidemiological and entomological post-intervention surveys over the course of a year and a half. Each epidemiological survey targeted 150 children per cluster, and entomological surveys targeted 25 houses. When the three surveys were combined, the median PCRPfPRs were 23% (IQR 8%) in the intervention arm and 42% (IQR 12%) in the control arm. The adjusted risk ratio (RR) was 0.53 [95% confidence interval (CI) 0.41–0.71; P = 0.029]. The median anopheline densities were 0.4 (IQR 0.4) and 2.0 (IQR 1.4), respectively. The adjusted RR was 0.41 (95% CI 0.29–0.90; P = 0.029). The present study indicates additional protection from insecticide-screened ceilings over the current best practice.

The taxonomy of the 10 recognized Neoechinorhynchus species associated with emydid turtles is complex due to the morphological conservatism. In the present study, specimens of N. emyditoides from northern and southeastern Mexico exhibit great phenotypic plasticity on its diagnostic characteristics. We sequenced three molecular markers: the internal transcribed spacers ITS1, ITS2 and 5.8S gene, the D2 + D3 domains of the large subunit from nuclear DNA and cytochrome c oxidase subunit I (cox1) from mitochondrial DNA. Sequences of the nuclear molecular markers were aligned and compared with other congeneric species associated with emydids available in GenBank. Phylogenetic analyses supported the polyphyly of Neoechinorhynchus. The species from emydids formed a clade, which was subdivided into five subclades that correspond with each species analysed (N. pseudemydis, N. chrysemydis, N. emydis, N. schmidti and N. emyditoides). To understand better the genetic structure of N. emyditoides a haplotype network was inferred with 29 cox1 sequences, revealing the presence of 13 haplotypes, two of which were shared and 11 were unique. The high values of fixation index, Fst (0.4227–0.8925) detected between the two populations from southeastern and the two from northern Mexico indicated low genetic flow among the populations. Our data suggest that the Neoechinorhynchus species associated with emydid turtles diversified in the eastern USA and that of N. emyditoides expanded its distribution range reached southeastern Mexico.

The present study provides new insight into suitable microsporidian–host associations. It relates regional and continental-wide host specialization in microsporidians infecting amphipods to degraded and recovering habitats across 2 German river catchments. It provides a unique opportunity to infer the persistence of parasites following anthropogenic disturbance and their establishment in restored rivers. Amphipods were collected in 31 sampling sites with differing degradation and restoration gradients. Specimens were morphologically (hosts) and molecularly identified (host and parasites). Amphipod diversity and abundance, microsporidian diversity, host phylogenetic specificity and continental-wide β-specificity were investigated and related to each other and/or environmental variables. Fourteen microsporidian molecular operational taxonomic units (MOTUs), mainly generalist parasites, infecting 6 amphipod MOTUs were detected, expanding the current knowledge on the host range by 17 interactions. There was no difference in microsporidian diversity and host specificity among restored and near-natural streams (Boye) or between those located in urban and rural areas (Kinzig). Similarly, microsporidian diversity was generally not influenced by water parameters. In the Boye catchment, host densities did not influence microsporidian MOTU richness across restored and near-natural sites. High host turnover across the geographical range suggests that neither environmental conditions nor host diversity plays a significant role in the establishment into restored areas. Host diversity and environmental parameters do not indicate the persistence and dispersal of phylogenetic host generalist microsporidians in environments that experienced anthropogenic disturbance. Instead, these might depend on more complex mechanisms such as the production of resistant spores, host switching and host dispersal acting individually or conjointly.

Trematodes are the main macroparasites in coastal waters. The most abundant and widespread form of these parasites is metacercaria. Their impact on their host fitness is considered relatively low but metacercarial larvae of some species can have deleterious effects on individuals and/or populations. This review focused on the cockle Cerastoderma edule and four species of the genus Himasthla; a common host–parasite system in marine coastal environments. Our aims were (1) to review literature concerning Himasthla continua, Himasthla elongata, Himasthla interrupta and Himasthla quissetensis in cockles; (2) to provide molecular signatures of these parasites and (3) to analyse infection patterns using a 20-year monthly database of cockle monitoring from Banc d'Arguin (France). Due to identification uncertainties, the analysis of the database was restricted to H. interrupta and H. quissetensis, and it was revealed that these parasites infect cockles of the same size range. The intensity of parasites increased with cockle size/age. During the colder months, the mean parasite intensity of a cockle cohort decreased, while infection occurred in the warmest season. No inter-specific competition between trematode parasites was detected. Furthermore, even if the intensity of H. interrupta or H. quissetensis infection fluctuated in different years, this did not modify the trematode community structure in the cockles. The intensity of infection of both species was also positively correlated with trematode species richness and metacercarial abundance. This study highlighted the possible detrimental role of Himasthla spp. in cockle population dynamics. It also revealed the risks of misidentification, which should be resolved by further molecular approaches.

In the present paper, we review two of the most neglected intestinal food-borne trematodiases: echinostomiasis, caused by members of the family Echinostomatidae, and gastrodiscoidiasis produced by the amphistome Gastrodiscoides hominis. Both parasitic infections are important intestinal food-borne diseases. Humans become infected after ingestion of raw or insufficiently cooked molluscs, fish, crustaceans, amphibians or aquatic vegetables. Thus, eating habits are essential to determine the distribution of these parasitic diseases and, traditionally, they have been considered as minor diseases confined to low-income areas, mainly in Asia. However, this scenario is changing and the population at risk are currently expanding in relation to factors such as new eating habits in developed countries, growing international markets, improved transportation systems and demographic changes. These aspects determine the necessity of a better understanding of these parasitic diseases. Herein, we review the main features of human echinostomiasis and gastrodiscoidiasis in relation to their biology, epidemiology, immunology, clinical aspects, diagnosis and treatment.

Angiostrongylus cantonensis is an invasive zoonotic nematode which causes eosinophilic meningitis in accidental hosts – vertebrates including humans – and is known to impact wildlife. Even though the parasite originates in Southeast Asia, it has spread worldwide, especially into fragile island ecosystems. The Canary Islands are a biodiversity hot spot with numerous endemic species affected by biological invasions. Among others, Rattus rattus and Rattus norvegicus threaten many endemic species by predation and may spread invasive pathogens, such as the rat lungworm A. cantonensis, which was first described in Tenerife in 2010. Since it is known that lizards can act as paratenic hosts for A. cantonensis and Gallotia galloti is a lizard abundant in Tenerife, the aim of this study was to reveal the role of these endemic lizards in the parasite's life cycle. Gallotia galloti were captured in Tegueste, Tenerife, and after euthanasia, liver and tail muscle samples were examined for the presence of A. cantonensis. During microscopic examination, 8/36 liver samples (22.2%) contained granulomas with nematode larvae. In total, 10/39 liver samples (25.6%) and 7/36 tail muscle samples (19.4%) were positive for A. cantonensis DNA using qPCR. This is a first report of a reptile endemic to the Canary Islands acting as paratenic host of A. cantonensis. The fact that the parasite is obviously well-established in the island ecosystem and exploits endemic lizards as hosts may have important implications for the parasite's ecoepidemiology. Moreover, the parasite might threaten other species which depend on lizards in the island trophic web.

The title of this article refers to Table 1 in Zhou (2022, Infectious diseases of poverty: progress achieved during the decade gone and perspectives for the future. Infectious Diseases of Poverty 11, 1), in which it is indicated that Paragonimus species, like many other foodborne trematodes, are ancient pathogens that are also re-emerging to cause disease in modern times. This article provides a general overview of Paragonimus species and the disease they cause. This is followed by comments on several specific topics of current interest: taxonomy and distribution of members of the genus; details of the life cycle; global and regional prevalence of paragonimiasis; genomics of lung flukes and possible effects of global environmental change. Unresolved questions relating to these topics are discussed and gaps in knowledge identified.

Cestodes of the genus Arostrilepis Mas-Coma and Tenora 1997 have a Holarctic distribution with 16 species occurring among 28 species of mostly arvicoline hosts. The type species of the genus is Arostrilepis horrida (von Linstow, 1901), described initially as Taenia horrida von Linstow, 1901, from murine rodents in Lower Saxony (Niedersachsen), Germany. Here we report the first helminth parasite from the mole-vole, Ellobius tancrei, in Mongolia which is the first subterranean rodent known to be infected with Arostrilepis in the Palearctic. In addition, we describe a new species: Arostrilepis batsaikhani n. sp. which most closely resembles A. microtis Gulyaev and Chechulin 1997, differing from this species with a genetic distance of about 4% (using cytochrome-b) and by having distinctly large cirrus spines, testes that are larger and fill the whole segment measured anterior–posterior and larger eggs.

The taxonomy of species of Bivesicula Yamaguti, 1934 is analysed for samples from holocentrid, muraenid and serranid fishes from Japan, Ningaloo Reef (Western Australia), the Great Barrier Reef (Queensland), New Caledonia and French Polynesia. Analysis of three genetic markers (cox1 mtDNA, ITS2 and 28S rDNA) identifies three strongly supported clades of species and suggests that Bivesicula as presently recognized is not monophyletic. On the basis of combined morphological, molecular and biological data, 10 species are distinguished of which five are proposed as new. Bivesicula Clade 1 comprises seven species of which three are effectively morphologically cryptic relative to each other; all seven infect serranids and four also infect holocentrids. Bivesicula Clade 2 comprises three species of which two are effectively morphologically cryptic relative to each other; all three infect serranids and one also infects a muraenid. Bivesicula Clade 3 comprises two known species from apogonids and a pomacentrid, and forms a clade with species of Paucivitellosus Coil, Reid & Kuntz, 1965 to the exclusion of other Bivesicula species. Taxonomy in this genus is made challenging by the combination of low resolving power of ribosomal markers, the existence of regional cox1 mtDNA populations, exceptional and unpredictable host-specificity and geographical distribution, and significant host-induced morphological variation.

Parasites display various degrees of host specificity, reflecting different coevolutionary histories with their hosts. Avian hosts follow multiple migration patterns representing short but also long distances. As parasites infecting migratory birds are subjected to multiple environmental and biotic changes through their flyways, migration may disrupt or strengthen cophylogenetic congruence between hosts and parasites. On the one hand, parasites might adapt to a single migratory host, evolving to cope with the specific challenges associated with the multiple habitats occupied by the host. On the other, as migrants can introduce parasites into new habitats, higher rates of host switching could also disrupt cophylogenetic patterns. We analysed whether migratory behaviour shapes avian haemosporidian parasite–host cophylogenetic congruence by testing if contributions of host–parasite links to overall congruence differ among resident and short-, variable- and long-distance migrants globally and within South America only. On both scales, we found significant overall cophylogenetic congruence by testing whether overall congruence differed between haemosporidian lineages and bird species. However, we found no difference in contribution towards congruence among links involving resident vs migratory hosts in both models. Thus, migratory behaviour neither weakens nor strengthens bird–haemosporidian cophylogenetic congruence, suggesting that other avian host traits are more influential in generating phylogenetic congruence in this host–parasite system.

Invasion and spread of alien species can drive ecosystem changes, such as, the dynamics of infectious diseases. The non-native, marine gastropod Crepidula fornicata has become established across European coastlines over the last century, but there remains little insight into its disease carrying capacity and potential role as a source/sink of parasites. To address this knowledge gap, we surveyed limpets from two sites in South Wales, UK for signatures of disease/pathology using polymerase chain reaction-based methods (haemolymph) and histology (solid tissue). We encountered trematode-like parasites in ~1% individuals (5 out of 462). Three limpets displayed gross damage in the gonad, i.e. castration, and encysted metacercariae were found in the muscle of two other individuals. On the basis of 28S rDNA and internal transcribed spacer 2 genomic targets, we identified the gonad-infecting trematodes as members of the family Microphallidae – putative novel species related to the genus Longiductotrema. Earlier reports suggest that C. fornicata is not a host for trematode parasites in either its native or alien range but may act as a sink due to its filter feeding lifestyle. We provide clear evidence that C. fornicata is parasitized by at least one trematode species at two sites in Wales, UK, and likely act as a spillback or accidental host among native littorinids.

Four fossil ticks (Arachnida: Parasitiformes: Ixodida) are described from mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar. Ixodes antiquorum sp. nov. (Ixodidae) is the first Mesozoic record of Ixodes and the oldest representative of the most species-rich extant tick genus. Its affinities appear to lie with modern Australian forms, consistent with the hypothesis that Burmese amber hosted Gondwanan faunal elements. Even more remarkable is Khimaira fossus gen. et sp. nov. which combines a body resembling that of a soft tick (Argasidae) with a basis capitulum more like that of a hard tick (Ixodidae). We refer it to Khimairidae fam. nov. as a possible transitional form between the two main families of ticks alive today. Another member of the extinct Deinocrotonidae is described as Deinocroton copia sp. nov., while the first described adult female for Cornupalpatum burmanicum is associated with a dinosaur feather barb.

Parasitic nematodes devastate human and animal health. The limited number of anthelmintics available is concerning, especially because of increasing drug resistance. Anthelmintics are commonly derived from natural products, e.g. fungi and plants. This investigation aimed to develop a high-throughput whole organism screening method based on a motility assay using the wMicroTracker system. Anthelmintic activity of extracts from Hawaiian fungi was screened against third-stage larvae of the parasitic nematode Angiostrongylus cantonensis, categorized according to the degree of motility reduction. Of the 108 crude samples and fractionated products, 48 showed some level of activity, with 13 reducing motility to 0–25% of the maximum exhibited, including two pure compounds, emethacin B and epicoccin E, neither previously known to exhibit anthelmintic properties. The process of bioassay-guided fractionation is illustrated in detail based on analysis of one of the crude extracts, which led to isolation of lamellicolic anhydride, a compound with moderate activity. This study validates the wMicroTracker system as an economical and high-throughput option for testing large suites of natural products against A. cantonensis, adds to the short list of diverse parasites for which it has been validated and highlights the value of A. cantonensis and Hawaiian fungi for discovery of new anthelmintics.

Earth is rapidly losing free-living species. Is the same true for parasitic species? To reveal temporal trends in biodiversity, historical data are needed, but often such data do not exist for parasites. Here, parasite communities of the past were reconstructed by identifying parasites in fluid-preserved specimens held in natural history collections. Approximately 2500 macroparasites were counted from 109 English Sole (Parophrys vetulus) collected between 1930 and 2019 in the Salish Sea, Washington, USA. Alpha and beta diversity were measured to determine if and how diversity changed over time. Species richness of parasite infracommunities and community dispersion did not vary over time, but community composition of decadal component communities varied significantly over the study period. Community dissimilarity also varied: prior to the mid-20th century, parasites shifted in abundance in a seemingly stochastic manner and, after this time period, a canalization of community change was observed, where species' abundances began to shift in consistent directions. Further work is needed to elucidate potential drivers of these changes and to determine if these patterns are present in the parasite communities of other fishes of the Salish Sea.

Infection by malaria parasites (Plasmodium spp.) remains one of the leading causes of morbidity and mortality, especially in tropical regions of the world. Despite the availability of malaria control tools such as integrated vector management and effective therapeutics, these measures have been continuously undermined by the emergence of vector resistance to insecticides or parasite resistance to frontline antimalarial drugs. Whilst the recent pilot implementation of the RTS,S malaria vaccine is indeed a remarkable feat, highly effective vaccines against malaria remain elusive. The barriers to effective vaccines result from the complexity of both the malaria parasite lifecycle and the parasite as an organism itself with consequent major gaps in our understanding of their biology. Historically and due to the practical and ethical difficulties of working with human malaria infections, research into malaria parasite biology has been extensively facilitated by animal models. Animals have been used to study disease pathogenesis, host immune responses and their (dys)regulation and further disease processes such as transmission. Moreover, animal models remain at the forefront of pre-clinical evaluations of antimalarial drugs (drug efficacy, mode of action, mode of resistance) and vaccines. In this review, we discuss commonly used animal models of malaria, the parasite species used and their advantages and limitations which hinder their extrapolation to actual human disease. We also place into this context the most recent developments such as organoid technologies and humanized mice.

Within-year variation in infection is a ubiquitous feature of natural populations, but is determined by a complex interplay of environmental, parasitological and host factors. At the same time, co-infection is the norm in the wild. Longitudinal dynamics of co-infecting parasites may therefore be further complicated by covariation across multiple parasites. Here, we used fecal parasite egg and oocyst counts collected repeatedly from individually marked wild Soay sheep to investigate seasonal dynamics of six gastrointestinal parasite groups. Prevalence and abundance tended to be higher in spring and summer, and abundance was higher in lambs compared to adults. We found that within-year variation in highly prevalent strongyle nematode counts was dependent on adult reproductive status, where reproductive ewes had distinct dynamics compared to males and barren ewes. For similarly prevalent coccidia we found an overall peak in oocyst counts in spring but no differences among males, barren and pregnant ewes. Using multivariate mixed-effects models, we further show that apparent positive correlation between strongyle and coccidia counts was driven by short-term within-individual changes in both counts rather than long-term among-individual covariation. Overall, these results demonstrate that seasonality varies across demographic and parasite groups and highlight the value of investigating co-infection dynamics over time.