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The identification of gastrointestinal helminth infections of humans and livestock almost exclusively relies on the detection of eggs or larvae in faeces, followed by manual counting and morphological characterisation to differentiate species using microscopy-based techniques. However, molecular approaches based on the detection and quantification of parasite DNA are becoming more prevalent, increasing the sensitivity, specificity and throughput of diagnostic assays. High-throughput sequencing, from single PCR targets through to the analysis of whole genomes, offers significant promise towards providing information-rich data that may add value beyond traditional and conventional molecular approaches; however, thus far, its utility has not been fully explored to detect helminths in faecal samples. In this study, low-depth whole genome sequencing, i.e. genome skimming, has been applied to detect and characterise helminth diversity in a set of helminth-infected human and livestock faecal material. The strengths and limitations of this approach are evaluated using three methods to characterise and differentiate metagenomic sequencing data based on (i) mapping to whole mitochondrial genomes, (ii) whole genome assemblies, and (iii) a comprehensive internal transcribed spacer 2 (ITS2) database, together with validation using quantitative PCR (qPCR). Our analyses suggest that genome skimming can successfully identify most single and multi-species infections reported by qPCR and can provide sufficient coverage within some samples to resolve consensus mitochondrial genomes, thus facilitating phylogenetic analyses of selected genera, e.g. Ascaris spp. Key to this approach is both the availability and integrity of helminth reference genomes, some of which are currently contaminated with bacterial and host sequences. The success of genome skimming of faecal DNA is dependent on the availability of vouchered sequences of helminths spanning both taxonomic and geographic diversity, together with methods to detect or amplify minute quantities of parasite nucleic acids in mixed samples., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Gender inequity in Science, Technology, Engineering, and Medicine (STEM) fields, including parasitology, continues to limit the participation of women in scientific leadership and development. Here we highlight the aims and activities of Herminthology, an initiative promoting the work of women in parasitology, alongside the current status quo of men and women scientists in the discipline., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Infections by gastrointestinal (GI) helminths have been associated with significant alterations of the structure of microbial communities inhabiting the host gut. However, current understanding of the biological mechanisms that regulate these relationships is still lacking. We propose that helminth-derived extracellular vesicles (EVs) likely represent key players in helminth-microbiota crosstalk. Here, we explore knowledge of helminth EVs with an emphasis on their putative antimicrobial properties, and we argue that (i) an enhanced understanding of the mechanisms governing such interactions might assist the discovery and development of novel strategies of parasite control, and that (ii) the identification and characterisation of helminth molecules with antimicrobial properties might pave the way towards the discovery of novel antibiotics, thus aiding the global fight against antimicrobial resistance., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Helminth infections impact the composition of the mammalian gut microbiota; however, the mechanisms underpinning these interactions are, thus far, unknown. In this article, we propose that microbiota-derived extracellular vesicles might represent key players in host-helminth-microbiome crosstalk, and outline future directions to elucidate their role(s) in host-parasite relationships., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

There is increasing attention on the complex interactions occurring between gastrointestinal parasitic helminths and the microbial flora (microbiota) inhabiting the host gut. However, little is known about the occurrence, structure, and function of microbial populations residing within parasite organs and tissues. In this article, we argue that an in-depth understanding of the interplay between parasites and their microbiomes may significantly enhance current knowledge of parasite biology and physiology, and may lead to the discovery of entirely novel, anthelmintic-independent interventions against parasites and parasitic diseases., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Whilst a wealth of data indicate that infections by gastrointestinal helminths are accompanied by significant alterations in the composition of the vertebrate gut flora, little is known of the immune-molecular mechanisms that regulate host-parasite-microbiota interactions. 'Traditional' experimental models of gastrointestinal helminthiases, in which the role(s) of each of the components of this triad can be tested, provide an opportunity to advance research in this area. In this article, we propose the Echinostoma caproni-mouse system as a potentially useful tool for studies of the role of the host gut microbiota in preventing pathology and inducing parasite clearance via interleukin (IL)-25, an epithelial-derived alarmin with key roles in antihelminth immunity and maintenance of gut homeostasis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A growing body of evidence, particularly in humans and rodents, supports the existence of a complex network of interactions occurring between gastrointestinal (GI) helminth parasites and the gut commensal bacteria, with substantial effects on both host immunity and metabolic potential. However, little is known of the fundamental biology of such interactions in other animal species; nonetheless, given the considerable economic losses associated with GI parasites, particularly in livestock and equines, as well as the global threat of emerging anthelmintic resistance, further explorations of the complexities of host-helminth-microbiota interactions in these species are needed. This study characterises the composition of the equine gut commensal flora associated with the presence, in faecal samples, of low (Clow) and high (Chigh) numbers of eggs of an important group of GI parasites (i.e. the cyathostomins), prior to and following anthelmintic treatment. High-throughput sequencing of bacterial 16S rRNA amplicons and associated bioinformatics and statistical analyses of sequence data revealed strong clustering according to faecal egg counts (P = 0.003). A trend towards increased populations of Methanomicrobia (class) and Dehalobacterium (genus) was observed in Clow in comparison with Chigh. Anthelmintic treatment in Chigh was associated with a significant reduction of the bacterial Phylum TM7 14 days post-ivermectin administration, as well as a transient expansion of Adlercreutzia spp. at 2 days post-treatment. This study provides a first known insight into the discovery of the intimate mechanisms governing host-parasite-microbiota interactions in equines, and sets a basis for the development of novel, biology-based intervention strategies against equine GI helminths based on the manipulation of the commensal gut flora., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

With the exception of Aelurostrongylus abstrusus, feline lungworms have been poorly studied. Information on their distribution is patchy and mostly limited to case reports. In this study, the occurrence of feline lungworms and co-infecting gastrointestinal parasites has been investigated in 12 European countries (i.e. Austria, Belgium, Bulgaria, France, Greece, Hungary, Italy, Portugal, Romania, Spain, Switzerland and the United Kingdom). An average of 10 domestic cats, with regular outdoor access, was sampled each month for 12months, and freshly passed faeces were collected. Stools were processed using a McMaster assay and a quantitative Baermann-Wetzel method. Animals positive for lungworms and/or gastrointestinal parasites were treated with a formulation containing fipronil, (S)-methoprene, eprinomectin, and praziquantel (Broadline®, Merial), and re-sampled 28days post-treatment. The association between lungworm infection and risk factors was analysed using statistical medians/means and the efficacy of the treatment against each lungworm species was assessed. Of 1990 cats sampled, 613 (30.8%) were positive for at least one parasite, while 210 (10.6%) were infected by lungworms. The prevalence of lungworm infection varied between the sampled sites, with the highest recorded in Bulgaria (35.8%) and the lowest in Switzerland (0.8%). None of the cats from Austria or the United Kingdom were infected by lungworms. Aelurostrongylus abstrusus was the species most frequently detected (78.1%), followed by Troglostrongylus brevior (19.5%), Eucoleus aerophilus (14.8%) and Oslerus rostratus (3.8%). The overall efficacy of the treatment was 99% for A. abstrusus and 100% for T. brevior, O. rostratus and E. aerophilus. Data presented provide a comprehensive account of the diagnosis, epidemiology and treatment of feline lungworms in Europe, as well as of the occurrence of co-infections by gastrointestinal parasites., (Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Gastrointestinal helminth parasites share their habitat with a myriad of other organisms, that is, the commensal microbiota. Increasing evidence, particularly in humans and rodent models of helminth infection, points towards a multitude of interactions occurring between parasites and the gut microbiota, with a profound impact on both host immunity and metabolic potential. Despite this information, the exploration of the effects that parasite infections exert on populations of commensal gut microbes of veterinary species is a field of research in its infancy. In this article, we summarise studies that have contributed to current knowledge of helminth-microbiota interactions in species of veterinary interest, and identify possible avenues for future research in this area, which could include the exploitation of such relationships to improve parasite control and delay or prevent the development of anthelmintic resistance., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

More than 300 million people suffer from a range of diseases caused by gastropod-borne helminths, predominantly flatworms and roundworms, whose life cycles are characterized by a diversified ecology and epidemiology. Despite the plethora of data on these parasites, very little is known of the fundamental biology of their gastropod intermediate hosts, or of the interactions occurring at the snail-helminth interface. In this article, we focus on schistosomes and metastrongylids of human and animal significance, and review current knowledge of snail-parasite interplay. Future efforts aimed at elucidating key elements of the biology and ecology of the snail intermediate hosts, together with an improved understanding of snail-parasite interactions, will aid to identify, plan, and develop new strategies for disease control focused on gastropod intermediate hosts., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

It has been nearly 10 years since the completion of the first entire genome sequence of a Leishmania parasite. Genomic and transcriptomic analyses have advanced our understanding of the biology of Leishmania, and shed new light on the complex interactions occurring within the parasite-host-vector triangle. Here, we review these advances and examine potential avenues for translation of these discoveries into treatment and control programs. In addition, we argue for a strong need to explore how disease in dogs relates to that in humans, and how an improved understanding in line with the 'One Health' concept may open new avenues for the control of these devastating diseases., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Compounded by a massive global food shortage, many parasitic diseases have a devastating, long-term impact on animal and human health and welfare worldwide. Parasitic helminths (worms) affect the health of billions of animals. Unlocking the systems biology of these neglected pathogens will underpin the design of new and improved interventions against them. Currently, the functional annotation of genomic and transcriptomic sequence data for socio-economically important parasitic worms relies almost exclusively on comparative bioinformatic analyses using model organism- and other databases. However, many genes and gene products of parasitic helminths (often >50%) cannot be annotated using this approach, because they are specific to parasites and/or do not have identifiable homologs in other organisms for which sequence data are available. This inability to fully annotate transcriptomes and predicted proteomes is a major challenge and constrains our understanding of the biology of parasites, interactions with their hosts and of parasitism and the pathogenesis of disease on a molecular level. In the present article, we compiled transcriptomic data sets of key, socioeconomically important parasitic helminths, and constructed and validated a curated database, called HelmDB (www.helmdb.org). We demonstrate how this database can be used effectively for the improvement of functional annotation by employing data integration and clustering. Importantly, HelmDB provides a practical and user-friendly toolkit for sequence browsing and comparative analyses among divergent helminth groups (including nematodes and trematodes), and should be readily adaptable and applicable to a wide range of other organisms. This web-based, integrative database should assist 'systems biology' studies of parasitic helminths, and the discovery and prioritization of novel drug and vaccine targets. This focus provides a pathway toward developing new and improved approaches for the treatment and control of parasitic diseases, with the potential for important biotechnological outcomes., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The genus Rhipicephalus (Acari: Ixodidae) comprises a large number of vectors of pathogens of substantial medical and veterinary concern; however, species identification based solely on morphological features is often challenging. In the present study, genetic distance within selected Rhipicephalus species (i.e., Rhipicephalus bursa, Rhipicephalus guilhoni, Rhipicephalus muhsamae, Rhipicephalus sanguineus sensu lato and Rhipicephalus turanicus), were investigated based on molecular and phylogenetic analyses of fragments of the mitochondrial 16S, 12S and cytochrome c oxidase subunit 1 (cox1) genes, as well as of the whole sequences of the ribosomal internal transcribed spacer-2 (ITS-2) region. Mean values of inter-specific genetic distance (e.g., up to 12.6%, 11.1% and 15.2%), as well as of intra-specific genetic distance (e.g., 0.9%, 0.9% and 1%), calculated using the Kimura-2 parameter substitution model with uniform rates among sites for 16S, 12S and cox1 genes, respectively, confirmed the differentiation of the rhipicephaline species herein examined. The molecular identification was also supported by the distinct separation of species-specific clades inferred from the phylogenetic analyses of all mitochondrial sequences. Conversely, little interspecific divergence was detected amongst ribosomal ITS-2 sequences (i.e., up to 2.8%) for species belonging to the R. sanguineus complex, which resulted in the ambiguous placement of selected R. sanguineus s.l. and R. turanicus sequences in the corresponding phylogenetic tree. Results from this study confirm the suitability of mtDNA markers for the reliable identification of ticks within the Rhipicephalus genus and provide a framework for future studies of taxonomy, speciation history and evolution of this group of ticks., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The advent and integration of high-throughput 'omic technologies (e.g., genomics, transcriptomics, proteomics and metabolomics) are becoming instrumental to assist fundamental explorations of the systems biology of organisms. In particular, these technologies now provide unique opportunities for global, molecular investigations of parasites. For example, studies of the transcriptomes (all transcripts in an organism, tissue or cell) of different species and/or developmental stages of parasitic nematodes provide insights into aspects of gene expression, regulation and function, which is a major step to understanding their biology. The purpose of this article was to review salient aspects of the systematics and biology of selected species of parasitic nematodes (particularly key species of the order Strongylida) of socio-economic importance, to describe conventional and advanced sequencing technologies and bioinformatic tools for large-scale investigations of the transcriptomes of these parasites and to highlight the prospects and implications of these explorations for developing novel methods of parasite intervention., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Bovine theileriosis is an arthropod-borne disease caused by one or more haemoprotozoan parasites of the genus Theileria. Traditionally, Theileria infection in cattle in Australia was largely asymptomatic and recognized to be associated with Theileria buffeli, now assigned to the Theileria orientalis-group. There have been some recent outbreaks of theileriosis in dairy and beef cattle, mainly in subtropical climatic zone (New South Wales) of Australia. Here, we provide the first published evidence of an outbreak of bovine theileriosis in the south-eastern Australia (state of Victoria) linked to the ikeda and chitose genotypes of T. orientalis. Future investigations should focus sharply on the elucidating the epidemiology and ecology of Theileria in this region to subvert the possible impact on the cattle industry., (Copyright © 2011. Published by Elsevier B.V.)

The lungworm, Dictyocaulus viviparus, causes parasitic bronchitis in cattle, and is responsible for substantial economic losses in temperate regions of the world. Here, we undertake the first large-scale exploration of available transcriptomic data for this lungworm, examine differences in transcription between different stages/both genders and identify and prioritize essential molecules linked to fundamental metabolic pathways, which could represent novel drug targets. Approximately 3 million expressed sequence tags (ESTs), generated by 454 sequencing from third-stage larvae (L3s) as well as adult females and males of D. viviparus, were assembled and annotated. The assembly of these sequences yielded ~61,000 contigs, of which relatively large proportions encoded collagens (4.3%), ubiquitins (2.1%) and serine/threonine protein kinases (1.9%). Subtractive analysis in silico identified 6928 nucleotide sequences as being uniquely transcribed in L3, and 5203 and 7889 transcripts as being exclusive to the adult female and male, respectively. Most peptides predicted from the conceptual translations were nucleoplasmins (L3), serine/threonine protein kinases (female) and major sperm proteins (male). Additional analyses allowed the prediction of three drug target candidates, whose Caenorhabditis elegans homologues were linked to a lethal RNA interference phenotype. This detailed exploration, combined with future transcriptomic sequencing of all developmental stages of D. viviparus, will facilitate future investigations of the molecular biology of this parasitic nematode as well as genomic sequencing. These advances will underpin the discovery of new drug and/or vaccine targets, focused on biotechnological outcomes., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Almost nothing is known about atypical kinases in multicellular organisms, including parasites. Supported by information and data available for the free-living nematode, Caenorhabditis elegans, and other eukaryotes, the present article describes three RIO kinase genes, riok-1, riok-2 and riok-3, from Haemonchus contortus, one of the most important parasitic nematodes of small ruminants. Analyses of these genes and their products predict that they each play critical roles in the developmental pathways of parasitic nematodes. The findings of this review indicate prospects for functional studies of these genes in C. elegans (as a surrogate) and opportunities for the design of a novel class of nematode-specific inhibitors of RIO kinases. The latter aspect is of paramount importance, given the serious problems linked to anthelmintic resistance in parasitic nematode populations of livestock., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Trichostrongylus colubriformis (Strongylida), a small intestinal nematode of small ruminants, is a major cause of production and economic losses in many countries. The aims of the present study were to define the transcriptome of the adult stage of T. colubriformis, using 454 sequencing technology and bioinformatic analyses, and to predict the main pathways that key groups of molecules are linked to in this nematode. A total of 21,259 contigs were assembled from the sequence data produced from a normalized cDNA library; 7876 of these contigs had known orthologues in the free-living nematode Caenorhabditis elegans, and encoded, amongst others, proteins with 'transthyretin-like' (8.8%), 'RNA recognition' (8.4%) and 'metridin-like ShK toxin' (7.6%) motifs. Bioinformatic analyses inferred that relatively high proportions of the C. elegans homologues are involved in biological pathways linked to 'peptidases' (4%), 'ribosome' (3.6%) and 'oxidative phosphorylation' (3%). Highly represented were peptides predicted to be associated with the nervous system, digestion of host proteins or inhibition of host proteases. Probabilistic functional gene networking of the complement of C. elegans orthologues (n=2126) assigned significance to particular subsets of molecules, such as protein kinases and serine/threonine phosphatases. The present study represents the first, comprehensive insight into the transcriptome of adult T. colubriformis, which provides a foundation for fundamental studies of the molecular biology and biochemistry of this parasitic nematode as well as prospects for identifying targets for novel nematocides. Future investigations should focus on comparing the transcriptomes of different developmental stages, both genders and various tissues of this parasitic nematode for the prediction of essential genes/gene products that are specific to nematodes., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Liver flukes, such as Clonorchis sinensis and Opisthorchis viverrini, are food-borne parasites that have a major impact on the health of humans and animals, particularly in Asia. However, the impact of C. sinensis and O. viverrini, in particular, is exacerbated in that these parasites can induce a malignant, untreatable cancer (cholangiocarcinoma, CCA) in chronically infected people. As a result, these flukes are classified as Group 1 carcinogens. Despite their substantial socio-economic importance, little is known about these parasites and their relationship with the definitive hosts at the molecular level. Here, we provide a background on these two carcinogenic flukes and review recent progress on characterizing their transcriptomes using next-generation technologies. We also describe the prospects that the transcriptomes of C. sinensis and O. viverrini provide as a resource for future -omic explorations and efforts to develop improved methods of intervention and control against these important pathogens and CCA, leading to biotechnological outcomes., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Liver flukes of animals are parasitic flatworms (Platyhelminthes: Digenea) of major socioeconomic importance in many countries. Key representatives, such as Fasciola hepatica and F. gigantica, cause "liver fluke disease" (= fascioliasis), which is of major animal health significance worldwide. In particular, F. hepatica is a leading cause of production losses to the livestock (mainly sheep and cattle) and meat industries due to clinical disease, reduced weight gain and milk production, and deaths. This parasite is also a major food-borne pathogen of humans throughout parts of the Middle East, Asia and South America. Currently, there is a significant focus on the development of new approaches for the prevention and control of fascioliasis in livestock. Recent technological advances in genomics and bioinformatics provide unique opportunities for the identification and prevalidation of drug targets and vaccines through a better understanding of the biology of F. hepatica and related species as well as their relationship with their hosts at the molecular level. Surprisingly, despite the widespread socioeconomic impact of fascioliasis, genomic datasets for F. hepatica are scant, limiting the molecular biological research of this parasite. The present article explores specifically the transcriptome of the adult stage of F. hepatica using an integrated genomic-bioinformatic platform. The analysis of the current data reveals numerous molecules of biological relevance, some of which are inferred to be involved in key biological processes or pathways that could serve as targets for new trematocidal drugs or vaccines. Improved insights into the transcriptome of F. hepatica should pave the way for future, comparative analysis of the transcriptomes of other developmental stages of this and related parasites, such as F. gigantica, cancer-causing flatworms (Clonorchis sinensis and Opisthorchis viverrini) and blood flukes (Schistosoma mansoni and S. japonicum). Prediction of the essentiality of genes and their products, molecular network connectivity of trematode genes as well as experimental exploration of function should also add value to the genomic discovery efforts in the future, focused on biotechnological outcomes., (Copyright 2009 Elsevier Inc. All rights reserved.)

A wide range of proteins belonging to the SCP/TAPS "family" has been described for various eukaryotic organisms, including plants and animals (vertebrates and invertebrates, such as helminths). Although SCP/TAPS proteins have been proposed to play key roles in a number of fundamental biological processes, such as host-pathogen interactions and defence mechanisms, there is a paucity of information on their genetic relationships, structures and functions, and there is no standardised nomenclature for these proteins. A detailed analysis of the relationships of members of the SCP/TAPS family of proteins, based on key protein signatures, could provide a foundation for investigating these areas. In this article, we review the current state of knowledge of key SCP/TAPS proteins of eukaryotes, with an emphasis on those from parasitic helminths, and undertake a comprehensive, systematic phylogenetic analysis of currently available full-length protein sequence data (considering characteristic protein signatures or motifs) to infer relationships and provide a framework (based on statistical support) for the naming of these proteins. This framework is intended to guide genomic and molecular biological explorations of key SCP/TAPS molecules associated with infectious diseases of plants and animals. In particular, fundamental investigations of these molecules in parasites and the integration of structural and functional data could lead to new and innovative approaches for the control of parasitic diseases, with important biotechnological outcomes.

Understanding the relationship between the gender of insects and their ability to act as vectors of insect-borne diseases (IBDs) could provide clues as to the origin of the intimate interplay among insect, pathogen and vertebrate hosts. The vector activity of several species of blood-feeding insects is linked to adult females. Interestingly, the only known exception is the transmission of canine and human thelaziosis by a male dipteran fly. This biological difference raises the question as to whether the parasitic behaviour of male and female insects transmitting IBDs is an expression of a co-evolution of vectors and pathogens.

Blood-feeding hookworms are parasitic nematodes of major human health importance. Currently, it is estimated that 740 million people are infected worldwide, and more than 80 million of them are severely affected clinically by hookworm disease. In spite of the health problems caused and the advances toward the development of vaccines against some hookworms, limited attention has been paid to the need for improved, practical methods of diagnosis. Accurate diagnosis and genetic characterization of hookworms is central to their effective control. While traditional diagnostic methods have considerable limitations, there has been some progress toward the development of molecular-diagnostic tools. The present article provides a brief background on hookworm disease of humans, reviews the main methods that have been used for diagnosis and describes progress in establishing polymerase chain reaction (PCR)-based methods for the specific diagnosis of hookworm infection and the genetic characterisation of the causative agents. This progress provides a foundation for the rapid development of practical, highly sensitive and specific diagnostic and analytical tools to be used in improved hookworm prevention and control programmes.

Knowledge about Phortica variegata (Drosophilidae, Steganinae), the intermediate host of the eyeworm Thelazia callipaeda (Spirurida, Thelaziidae), is confined to experimental studies. To investigate the role P. variegata plays in the transmission of T. callipaeda under natural conditions, the population dynamics of these flies in the natural environment and their feeding preferences (on vegetables and/or animal lachrymal secretions) were examined. From April to November 2005, a total number of 969 (557 males and 412 females) P. variegata flies were collected weekly in a region of southern Italy with a history of canine thelaziosis. The flies were identified and dissected or subjected to a PCR assay specific for a region within the ribosomal ITS-1 DNA of T. callipaeda. The zoophilic preferences of P. variegata were assessed by collecting flies around the eyes of a person or around a fruit bait. Seven hundred and twenty flies (398 males and 322 females) were dissected under a stereomicroscope; 249 flies (158 males and 91 females) that died prior to the dissection were subjected to molecular investigation. Only P. variegata males were infected with larval T. callipaeda both at dissection (six, 0.83%) and with the specific PCR (seven, 2.81%), representing a total percentage of 1.34% flies infected. Interestingly, only males were collected around the eyes, compared with a male/female ratio of 1:4 around the fruit. This survey indicated that P. variegata males act as intermediate hosts of T. callipaeda under natural conditions in Europe. Both the zoophilic behaviour of P. variegata males on lachrymal secretions and their role as vector of T. callipaeda have been discussed as they represent a peculiarity in medical and veterinary entomology. The synchrony between the fly population dynamics and the biology of the nematode in the definitive host provides an interesting model for exploring the co-evolution of Thelazia spp. with their hosts.