Population genomics of helminth parasites.

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.

Is the world wormier than it used to be? We'll never know without natural history collections.

Many disease ecologists and conservation biologists believe that the world is wormier than it used to be-that is, that parasites are increasing in abundance through time. This argument is intuitively appealing. Ecologists typically see parasitic infections, through their association with disease, as a negative endpoint, and are accustomed to attributing negative outcomes to human interference in the environment, so it slots neatly into our worldview that habitat destruction, biodiversity loss and climate change should have the collateral consequence of causing outbreaks of parasites. But surprisingly, the hypothesis that parasites are increasing in abundance through time remains entirely untested for the vast majority of wildlife parasite species. Historical data on parasites are nearly impossible to find, which leaves no baseline against which to compare contemporary parasite burdens. If we want to know whether the world is wormier than it used to be, there is only one major research avenue that will lead to an answer: parasitological examination of specimens preserved in natural history collections. Recent advances demonstrate that, for many specimen types, it is possible to extract reliable data on parasite presence and abundance. There are millions of suitable specimens that exist in collections around the world. When paired with contemporaneous environmental data, these parasitological data could even point to potential drivers of change in parasite abundance, including climate, pollution or host density change. We explain how to use preserved specimens to address pressing questions in parasite ecology, give a few key examples of how collections-based parasite ecology can resolve these questions, identify some pitfalls and workarounds, and suggest promising areas for research. Natural history specimens are 'parasite time capsules' that give ecologists the opportunity to test whether infectious disease is on the rise and to identify what forces might be driving these changes over time. This approach will facilitate major advances in a new sub-discipline: the historical ecology of parasitism.

What is in a name? Anopheles darlingi versus Nyssorhynchus darlingi.

Taxonomic reassignments were suggested for Neotropical anopheline malaria vectors, elevating four monophyletic groups Kerteszia, Lophopodomyia, Nyssorhynchus, and Stethomyia to the genus level, upending their conventional status as subgenera of the genus Anopheles. Two questions are proposed. Do the advantages of reclassification outweigh its disadvantages? Is the reclassification generally accepted and/or scientifically imperative?

Centering the Voices of Black Parasitologists During America's Racial Awakening.

During the fall of 2020, several panel discussions were held to highlight the perspectives of Black parasitologists. Here, I summarize the themes from three such discussions, held at the Molecular Parasitology Meeting, Black in Microbiology Week, and the Annual Meeting of the American Society of Tropical Medicine & Hygiene, respectively.

Network Analysis: Ten Years Shining Light on Host-Parasite Interactions.

Biological interactions are key drivers of ecological and evolutionary processes. The complexity of such interactions hinders our understanding of ecological systems and our ability to make effective predictions in changing environments. However, network analysis allows us to better tackle the complexity of ecosystems because it extracts the properties of an ecological system according to the number and distribution of links among interacting entities. The number of studies using network analysis to solve ecological and evolutionary questions in parasitology has increased over the past decade. Here, we synthesise the contribution of network analysis toward disentangling host-parasite processes. Furthermore, we identify current trends in mainstream ecology and novel applications of network analysis that present opportunities for research on host-parasite interactions.

iParasitology: Mining the Internet to Test Parasitological Hypotheses.

Digital data (internet queries, page views, social media posts, images) are accumulating online at increasing rates. Tools for compiling these data and extracting their metadata are now readily available. We highlight the possibilities and limitations of internet data to reveal patterns in host-parasite interactions and encourage parasitologists to embrace iParasitology.

Molecular Epidemiology of Giardia Infections in the Genomic Era.

Giardia duodenalis is a major gastrointestinal parasite of humans and animals across the globe. It is also of interest from an evolutionary perspective as it possesses many features that are unique among the eukaryotes, including its distinctive binucleate cell structure. While genomic analysis of a small number of isolates has provided valuable insights, efforts to understand the epidemiology of the disease and the population biology of the parasite have been limited by the molecular tools currently available. We review these tools and assess the impact of affordable and rapid genome sequencing systems increasingly being deployed in diagnostic settings. While these technologies have direct implications for public and veterinary health, they will also improve our understanding of the unique biology of this fascinating parasite.

Recent Advances in the Roles of Neutrophils in Toxoplasmosis.

Neutrophils are now recognized as major components of the response to Toxoplasma gondii by their contribution to parasite elimination by a number of mechanisms. This article focuses on recent advances in the understanding of the mechanisms of migration, cytokine release, and formation of extracellular traps by neutrophils during toxoplasmosis.

30 years of parasitology research analysed by text mining.

Bibliometric methods were used to analyse the major research trends, themes and topics over the last 30 years in the parasitology discipline. The tools used were SciMAT, VOSviewer and SWIFT-Review in conjunction with the parasitology literature contained in the MEDLINE, Web of Science, Scopus and Dimensions databases. The analyses show that the major research themes are dynamic and continually changing with time, although some themes identified based on keywords such as malaria, nematode, epidemiology and phylogeny are consistently referenced over time. We note the major impact of countries like Brazil has had on the literature of parasitology research. The increase in recent times of research productivity on 'antiparasitics' is discussed, as well as the change in emphasis on different antiparasitic drugs and insecticides over time. In summary, innovation in parasitology is global, extensive, multidisciplinary, constantly evolving and closely aligned with the availability of technology.

Humanized Mice and the Rebirth of Malaria Genetic Crosses.

The first experimental crosses carried out with the human malaria parasite Plasmodium falciparum played a key role in determining the genetic loci responsible for drug resistance, virulence, invasion, growth rate, and transmission. These crosses relied on splenectomized chimpanzees to complete the liver stage of the parasite's life cycle and the subsequent transition to asexual blood stage culture followed by cloning of recombinant progeny in vitro. Crosses can now be routinely carried out using human-liver-chimeric mice infused with human erythrocytes to generate hundreds of unique recombinant progeny for genetic linkage mapping, bulk segregant analysis, and high-throughput 'omics readouts. The high number of recombinant progeny should allow for unprecedented power and efficiency in the execution of a systems genetics approach to study P. falciparum biology.

Gene Editing in Trypanosomatids: Tips and Tricks in the CRISPR-Cas9 Era.

Gene editing in trypanosomatids has long been proven difficult. The development of CRISPR-Cas9 has improved this issue, opening the way to a better understanding of biological processes and drug-resistance mechanisms, and screening of drug targets. Different strategies have now been developed: either PCR- or plasmid-based, differing mainly in the nature of the donor DNA and the single guide RNA transcription. Here we review the main genetic tools available for Leishmania spp., Trypanosoma cruzi, and Trypanosoma brucei for gene tagging, single-base editing, and deletion of nonessential and essential genes. We discuss the main advantages and challenges of different strategies and how to choose 'the right cut' depending on the importance of untranslated regions. These considerations allow selection of the most accurate gene editing approach for a given functional analysis.

Towards a mechanistic understanding of competence: a missing link in diversity-disease research.

Biodiversity loss may increase the risk of infectious disease in a phenomenon known as the dilution effect. Circumstances that increase the likelihood of disease dilution are: (i) when hosts vary in their competence, and (ii) when communities disassemble predictably, such that the least competent hosts are the most likely to go extinct. Despite the central role of competence in diversity-disease theory, we lack a clear understanding of the factors underlying competence, as well as the drivers and extent of its variation. Our perspective piece encourages a mechanistic understanding of competence and a deeper consideration of its role in diversity-disease relationships. We outline current evidence, emerging questions and future directions regarding the basis of competence, its definition and measurement, the roots of its variation and its role in the community ecology of infectious disease.

[Update on the diagnosis of parasitic and fungal infections]. / Actualités du diagnostic des infections parasitaires et fongiques.

The diagnosis of parasitic and fungal infections, historically based on the detection of these pathogens using direct diagnosis (macro/microscopic examination, culture) or serological methods, has considerably evolved in the last decades, especially with the development of molecular approaches and mass spectrometry. These techniques, as well as most analyses of parasitic and fungal serology, are mostly the preserve of Hospital University Centers Parasitology-Mycology laboratories. In 2016, the French association of medical parasitology and mycology teachers and hospital practitioners (Anofel) has provided a Catalogue of rare analyses, regularly updated and freely accessible on the Anofel website (https://anofel.net/). This tool, which hinges on 4 parts (parasitology, parasitic serology, mycology, and fungal serology), aims to provide information on all available analyses, and a list of hospital laboratories able to undertake them. It is complementary to the other reference works that were developed by our association, including the Guide of analyses and methods in parasitology and mycology, published in 2018, and the eANOFEL pictures and videos database, freely accessible online (http://www.eanofel.fr). In this article, we draw-up a state-of-the-art of the most specialized techniques available in the parasitology-mycology laboratories and presented in the Catalogue of rare analyses of the Anofel collegium, and their interest for the diagnosis of these infections.

Building Parasitology Communities to Promote Gender Equality.

In an ideal world, there are equal opportunities for women to enter and progress in all scientific disciplines without bias or prejudice. Here, we share our experiences in building communities of women parasitology and offer easy-to-implement guidelines for scientists and institutions to overcome unconscious bias and create environments with better gender equality and diversity.

Post-genomic progress in helminth parasitology.

Helminth parasitology is an important discipline, which poses often unique technical challenges. One challenge is that helminth parasites, particularly those in humans, are often difficult to obtain alive and in sufficient quantities for study; another is the challenge of studying these organisms in vitro - no helminth parasite life cycle has been fully recapitulated outside of a host. Arguably, the key issue retarding progress in helminth parasitology has been a lack of experimental tools and resources, certainly relative to the riches that have driven many parasitologists to adopt free-living model organisms as surrogate systems. In response to these needs, the past 10-12 years have seen the beginnings of helminth parasitology's journey into the 'omics' era, with the release of abundant sequencing resources, and the functional genomics tools with which to test biological hypotheses. To reflect this progress, the 2019 Autumn Symposium of the British Society for Parasitology was held in Queen's University Belfast on the topic of 'post-genomic progress in helminth parasitology'. This issue presents examples of the current state of play in the field, while this editorial summarizes how genomic datasets and functional genomic tools have stimulated impressive recent progress in our understanding of parasite biology.

Update on BEI Resources for Parasitology and Arthropod Vector Research.

BEI Resources has contributed to the advancement of parasitic diseases research for over 16 years. The accessibility of our reference strains and reagents is relevant to the development of new therapeutics and vaccines. Here we provide a resource update with emphasis on the new assets for toxoplasmosis and vector research.

Parasites and Parasitology in this SARS-CoV-2, COVID-19 World: An American Society of Parasitologists Presidential Address.

The novel coronavirus disease 2019 (COVID-19) is one of the worst global health crises of this generation. The core of this pandemic is the rapid transmissibility of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, its high morbidity and mortality, and the presence of infectious asymptomatic carriers. As a result, COVID-19 has dominated this year's headlines and commanded significant research attention. As we consider SARS-CoV-2 and the COVID-19 pandemic, it is essential that scientists, governments, the media, and the general population also come to grips with the everyday cost of parasitic diseases. Plasmodium (malaria), schistosomes, filarial worms, hookworms, Ascaris, whipworms, and other protozoan and metazoan parasites take a tremendous toll on local communities. Yet, because most of these diseases are no longer endemic to developed countries, their research and intervention are not funded at levels that are proportional to their global morbidity and mortality. The scientific and public health communities must indeed vigorously fight SARS-CoV-2 and COVID-19, but while doing so and beyond, it will be essential to demonstrate steadfast resolve toward understanding and combating the parasitic diseases that for centuries have haunted humankind.

Organoids for Liver Stage Malaria Research.

Plasmodium parasites cause malaria and are maintained between Anopheles mosquitoes and mammalian hosts in a complex life cycle. Malaria parasites occupy tissue niches that can be difficult to access, and models to study them can be challenging to recapitulate experimentally, particularly for Plasmodium species that infect humans. 2D culture models provide extremely beneficial tools to investigate Plasmodium biology but they have limitations. More complex 3D structural networks, such as organoids, have unveiled new avenues for developing more physiological tissue models, and their application to malaria research offers great promise. Here, we review current models for studying Plasmodium infection with a key focus on the obligate pre-erythrocytic stage that culminates in blood infection, causing malaria, and discuss how organoids should fulfil an important and unmet need.