The Journal of Helminthology (JHL) was first published in 1923 and was originally created as a house journal of the London School of Hygiene and Tropical Medicine. The JHL was devised by its first Editor, Robert Leiper, to allow for rapid publication of results from the Department of Helminthology and its offshoot the Institute of Agricultural Parasitology. From this initial narrow focus the JHL has subsequently become not only internationally recognized but also retained its original emphasis on morphological, taxonomic and life cycle studies while embracing the emergence of new fields and technological advancements. The present review covers the historical development of the JHL over the last century from 1923 to 2023.

Fish parasitological research associated with fisheries and aquaculture has expanded remarkably over the past century. The application of parasites as biological tags has been one of the fields in which fish parasitology has generated new insight into fish migration and stock assessments worldwide. It is a well-established discipline whose methodological issues are regularly reviewed and updated. Therefore, no concepts or case-studies will be repeated here; instead, we summarize some of the main recent findings and achievements of this methodology. These include the extension of its use in hosts other than bony fishes; the improvements in the selection of parasite tags; the recognition of the host traits affecting the use of parasite tags; and the increasingly recognized need for integrative, multidisciplinary studies combining parasites with classical methods and modern techniques, such as otolith microchemistry and genetics. Archaeological evidence points to the existence of parasitic problems associated with aquaculture activities more than a thousand years ago. However, the main surge of research within aquaculture parasitology occurred with the impressive development of aquaculture over the past century. Protozoan and metazoan parasites, causing disease in domesticated fish in confined environments, have attracted the interest of parasitologists and, due to their economic importance, funding was made available for basic and applied research. This has resulted in a profusion of basic knowledge about parasite biology, physiology, parasite–host interactions, life cycles and biochemistry. Due to the need for effective control methods, various solutions targeting host–parasite interactions (immune responses and host finding), genetics and pharmacological aspects have been in focus.

Many of the most contentious questions that concern the ecology of helminths could be resolved with data on helminth abundance over the past few decades or centuries, but unfortunately these data are rare. A new sub-discipline – the historical ecology of parasitism – is resurrecting long-term data on the abundance of parasites, an advancement facilitated by the use of biological natural history collections. Because the world's museums hold billions of suitable specimens collected over more than a century, these potential parasitological datasets are broad in scope and finely resolved in taxonomic, temporal and spatial dimensions. Here, we set out best practices for the extraction of parasitological information from natural history collections, including how to conceive of a project, how to select specimens, how to engage curators and receive permission for proposed projects, standard operating protocols for dissections and how to manage data. Our hope is that other helminthologists will use this paper as a reference to expand their own research programmes along the dimension of time.

Schistosomiasis remains a major neglected tropical disease that afflicts over 200 million people globally. Schistosomes, the aetiological agent of schistosomiasis, are parasitic flatworms that propagate between molluscan and mammalian hosts. Inside the mammalian host, schistosomes rapidly grow over 100-fold in size and develop into a sexually mature male or female that thrives in the bloodstream for several decades. Recent work has identified schistosome stem cells as the source that drives parasite transmission, reproduction and longevity. Moreover, studies have begun to uncover molecular programmes deployed by stem cells that are essential for tissue development and maintenance, parasite survival and immune evasion. Such programmes are reminiscent of neoblast-driven development and regeneration of planarians, the free-living flatworm relative of schistosomes. Over the last few decades, research in planarians has employed modern functional genomic tools that significantly enhanced our understanding of stem cell-driven animal development and regeneration. In this review, we take a broad stroke overview of major flatworm organ systems at the cellular and molecular levels. We summarize recent advances on genetic regulators that play critical roles in differentiation and maintenance of flatworm cell types. Finally, we provide perspectives on how investigation of basic parasite biology is critical to discovering new approaches to battle schistosomiasis.

Helminth zoonoses remain a global problem to public health and the economy of many countries. Polymerase chain reaction-based techniques and sequencing have resolved many taxonomic issues and are now essential to understanding the epidemiology of helminth zoonotic infections and the ecology of the causative agents. This is clearly demonstrated from research on Echinococcus (echinococcosis) and Trichinella (trichinosis). Unfortunately, a variety of anthropogenic factors are worsening the problems caused by helminth zoonoses. These include cultural factors, urbanization and climate change. Wildlife plays an increasingly important role in the maintenance of many helminth zoonoses making surveillance and control increasingly difficult. The emergence or re-emergence of helminth zoonoses such as Ancylostoma ceylanicum, Toxocara, Dracunculus and Thelazia exacerbate an already discouraging scenario compounding the control of a group of long neglected diseases.

The evolution of helminth parasites has long been seen as an interplay between host resistance to infection and the parasite's capacity to bypass such resistance. However, there has recently been an increasing appreciation of the role of symbiotic microbes in the interaction of helminth parasites and their hosts. It is now clear that helminths have a different microbiome from the organisms they parasitize, and sometimes amid large variability, components of the microbiome are shared among different life stages or among populations of the parasite. Helminths have been shown to acquire microbes from their parent generations (vertical transmission) and from their surroundings (horizontal transmission). In this latter case, natural selection has been strongly linked to the fact that helminth-associated microbiota is not simply a random assemblage of the pool of microbes available from their organismal hosts or environments. Indeed, some helminth parasites and specific microbial taxa have evolved complex ecological relationships, ranging from obligate mutualism to reproductive manipulation of the helminth by associated microbes. However, our understanding is still very elementary regarding the net effect of all microbiome components in the eco-evolution of helminths and their interaction with hosts. In this non-exhaustible review, we focus on the bacterial microbiome associated with helminths (as opposed to the microbiome of their hosts) and highlight relevant concepts and key findings in bacterial transmission, ecological associations, and taxonomic and functional diversity of the bacteriome. We integrate the microbiome dimension in a discussion of the evolution of helminth parasites and identify fundamental knowledge gaps, finally suggesting research avenues for understanding the eco-evolutionary impacts of the microbiome in host–parasite interactions in light of new technological developments.

Next generation sequencing technologies have facilitated a shift from a few targeted loci in population genetic studies to whole genome approaches. Here, we review the types of questions and inferences regarding the population biology and evolution of parasitic helminths being addressed within the field of population genomics. Topics include parabiome, hybridization, population structure, loci under selection and linkage mapping. We highlight various advances, and note the current trends in the field, particularly a focus on human-related parasites despite the inherent biodiversity of helminth species. We conclude by advocating for a broader application of population genomics to reflect the taxonomic and life history breadth displayed by helminth parasites. As such, our basic knowledge about helminth population biology and evolution would be enhanced while the diversity of helminths in itself would facilitate population genomic comparative studies to address broader ecological and evolutionary concepts.

Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as well as for pathogen transmission and infectious disease dynamics. This has been particularly well-documented for the cercaria free-living stage of digenean trematode parasites within the Phylum Platyhelminthes. Here, we aim to synthesize the current state of knowledge regarding cercariae consumption by examining: (a) approaches for studying cercariae consumption; (b) the range of consumers and trematode prey documented thus far; (c) factors influencing the likelihood of cercariae consumption; (d) consequences of cercariae consumption for individual predators (e.g. their viability as a food source); and (e) implications of cercariae consumption for entire communities and ecosystems (e.g. transmission, nutrient cycling and influences on other prey). We detected 121 unique consumer-by-cercaria combinations that spanned 60 species of consumer and 35 trematode species. Meaningful reductions in transmission were seen for 31 of 36 combinations that considered this; however, separate studies with the same cercaria and consumer sometimes showed different results. Along with addressing knowledge gaps and suggesting future research directions, we highlight how the conceptual and empirical approaches discussed here for consumption of cercariae are relevant for the infectious stages of other parasites and pathogens, illustrating the use of cercariae as a model system to help advance our knowledge regarding the general importance of parasite consumption.

The world's biodiversity is in peril. The major threats to biodiversity globally are habitat change, overexploitation, climate change, invasive species and pollution. Not only do these stressors impact free-living organisms, but they affect parasitic ones as well. Herein, this perspective examines the potential consequences of these anthropogenic perturbations on helminth populations and communities, with emphasis on significant developments over the past decade. Furthermore, several case studies are examined in more detail for each of these threats to biodiversity. While effects are widespread and diverse, for the most part all these environmental stressors have negative effects on parasite populations and communities. Those parasites with complex life cycles that are trophically transmitted are often more at risk, although larval parasites with a wide host spectrum, and directly transmitted ectoparasites, appear less threatened and may even benefit. However, differential effects on hosts and parasites, on parasite life cycle stages and on host–parasite interactions made specific predictions difficult and context-dependent. Experimental laboratory and mesocosm studies on specific parasites that test effects on the different life cycle stages, hosts and host–parasite interactions, permitting the determination of net effects of an environmental stressor, yield insightful and sometimes counterintuitive results, although they remain a simplification of real-world complexity. Recent advances in the use of parasites as bioindicators of effects also are discussed.