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Seminars in Immunopathology Jun 2020Schistosomiasis (bilharzia) is a neglected tropical disease caused by trematode worms of the genus Schistosoma. The transmission cycle involves human (or other... (Review)
Review
Schistosomiasis (bilharzia) is a neglected tropical disease caused by trematode worms of the genus Schistosoma. The transmission cycle involves human (or other mammalian) water contact with surface water contaminated by faeces or urine, as well as specific freshwater snails acting as intermediate hosts. The main disease-causing species are S. haematobium, S. mansoni and S. japonicum. According to the World Health Organisation, over 250 million people are infected worldwide, leading to considerable morbidity and the estimated loss of 1.9 million disability-adjusted life years (DALYs), a likely underestimated figure. Schistosomiasis is characterised by focal epidemiology and an over-dispersed population distribution, with higher infection rates in children. Complex immune mechanisms lead to the slow acquisition of immune resistance, but innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is most evident in travellers following a primary infection. Chronic schistosomiasis affects mainly individuals with long-standing infections residing in poor rural areas. Immunopathological reactions against schistosome eggs trapped in host tissues lead to inflammatory and obstructive disease in the urinary system (S. haematobium) or intestinal disease, hepatosplenic inflammation and liver fibrosis (S. mansoni and S. japonicum). An effective drug-praziquantel-is available for treatment but, despite intensive efforts, no schistosomiasis vaccines have yet been accepted for public use. In this review, we briefly introduce the schistosome parasites and the immunopathogenic manifestations resulting from schistosomiasis. We then explore aspects of the immunology and host-parasite interplay in schistosome infections paying special attention to the current status of schistosomiasis vaccine development highlighting the advancement of a new controlled human challenge infection model for testing schistosomiasis vaccines.
Topics: Animals; Anthelmintics; Child; Humans; Schistosoma haematobium; Schistosoma mansoni; Schistosomiasis; Vaccines
PubMed: 32076812
DOI: 10.1007/s00281-020-00789-x -
Veterinary Parasitology Jun 2023The faecal egg count reduction test (FECRT) remains the method of choice for establishing the efficacy of anthelmintic compounds in the field, including the diagnosis of... (Review)
Review
World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guideline for diagnosing anthelmintic resistance using the faecal egg count reduction test in ruminants, horses and swine.
The faecal egg count reduction test (FECRT) remains the method of choice for establishing the efficacy of anthelmintic compounds in the field, including the diagnosis of anthelmintic resistance. We present a guideline for improving the standardization and performance of the FECRT that has four sections. In the first section, we address the major issues relevant to experimental design, choice of faecal egg count (FEC) method, statistical analysis, and interpretation of the FECRT results. In the second section, we make a series of general recommendations that are applicable across all animals addressed in this guideline. In the third section, we provide separate guidance details for cattle, small ruminants (sheep and goats), horses and pigs to address the issues that are specific to the different animal types. Finally, we provide overviews of the specific details required to conduct an FECRT for each of the different host species. To address the issues of statistical power vs. practicality, we also provide two separate options for each animal species; (i) a version designed to detect small changes in efficacy that is intended for use in scientific studies, and (ii) a less resource-intensive version intended for routine use by veterinarians and livestock owners to detect larger changes in efficacy. Compared to the previous FECRT recommendations, four important differences are noted. First, it is now generally recommended to perform the FECRT based on pre- and post-treatment FEC of the same animals (paired study design), rather than on post-treatment FEC of both treated and untreated (control) animals (unpaired study design). Second, instead of requiring a minimum mean FEC (expressed in eggs per gram (EPG)) of the group to be tested, the new requirement is for a minimum total number of eggs to be counted under the microscope (cumulative number of eggs counted before the application of a conversion factor). Third, we provide flexibility in the required size of the treatment group by presenting three separate options that depend on the (expected) number of eggs counted. Finally, these guidelines address all major livestock species, and the thresholds for defining reduced efficacy are adapted and aligned to host species, anthelmintic drug and parasite species. In conclusion, these new guidelines provide improved methodology and standardization of the FECRT for all major livestock species.
Topics: Animals; Horses; Cattle; Sheep; Swine; Parasite Egg Count; Ovum; Anthelmintics; Feces; Goats; Drug Resistance
PubMed: 37121092
DOI: 10.1016/j.vetpar.2023.109936 -
Trends in Parasitology Jan 2021Here we tell the story of ivermectin, describing its anthelmintic and insecticidal actions and recent studies that have sought to reposition ivermectin for the treatment... (Review)
Review
Here we tell the story of ivermectin, describing its anthelmintic and insecticidal actions and recent studies that have sought to reposition ivermectin for the treatment of other diseases that are not caused by helminth and insect parasites. The standard theory of its anthelmintic and insecticidal mode of action is that it is a selective positive allosteric modulator of glutamate-gated chloride channels found in nematodes and insects. At higher concentrations, ivermectin also acts as an allosteric modulator of ion channels found in host central nervous systems. In addition, in tissue culture, at concentrations higher than anthelmintic concentrations, ivermectin shows antiviral, antimalarial, antimetabolic, and anticancer effects. Caution is required before extrapolating from these preliminary repositioning experiments to clinical use, particularly for Covid-19 treatment, because of the high concentrations of ivermectin used in tissue-culture experiments.
Topics: Animals; Anthelmintics; Antimalarials; Antineoplastic Agents; Antiviral Agents; Cell Line; Chloride Channels; Dengue Virus; Insecticides; Ion Channels; Ivermectin; Nematoda; SARS-CoV-2; COVID-19 Drug Treatment
PubMed: 33189582
DOI: 10.1016/j.pt.2020.10.005 -
Journal of Traditional Chinese Medicine... Aug 2022Helminths or Parasitic worms of humans may cause chronic and sometimes deadly diseases, considered as neglected tropical diseases (NTDs) that infect around two billion... (Review)
Review
Helminths or Parasitic worms of humans may cause chronic and sometimes deadly diseases, considered as neglected tropical diseases (NTDs) that infect around two billion people worldwide. Plants have been used as anthelmintics from ancient times. This review is a compilation of plants as source of anthelmintic drug. All information presented in this review article regarding the anthelmintic activities of plants from 2005 and has been acquired by approaching various electronic databases, including Scopus, Google scholar, Web of science and PubMed. Literature was surveyed for anthelmintic activity of plants which showed that secondary metabolites of plants like terpenes, glycosides, saponins, flavonoids, tannins and alkaloids were having anthelmintic activity. Since this review is a compilation of anthelmintic activity of plants from the year 2005, it will definitely be a fruitful study for researchers working in this field.
Topics: Anthelmintics; Flavonoids; Humans; Plant Extracts; Saponins
PubMed: 35848982
DOI: 10.19852/j.cnki.jtcm.2022.04.007 -
Molecules (Basel, Switzerland) Nov 2022Helminths, with an estimated 1.5 billion annual global infections, are one of the major health challenges worldwide. The current strategy of the World Health... (Review)
Review
Helminths, with an estimated 1.5 billion annual global infections, are one of the major health challenges worldwide. The current strategy of the World Health Organization to prevent helminth infection includes increasing hygienic awareness, providing better sanitation and preventative anthelmintic drug therapy in vulnerable populations. Nowadays, anthelmintic drugs are used heavily in livestock, both in case of infection and as a preventative measure. However, this has led to the development of resistance against several of the most common drugs, such as levamisole, ivermectin and thiabendazole. As many as 70% of the livestock in developed countries now has helminths that are drug resistant, and multiple resistance is common. Because of this, novel anthelmintics are urgently needed to help combat large-scale production losses. Prior to this review, no comprehensive review of the anthelmintic effects of essential oils and their components existed. Multiple review articles have been published on the uses of a single plant and its extracts that only briefly touch upon their anthelmintic activity. This review aims to provide a detailed overview of essential oils and their components as anthelmintic treatment against a wider variety of helminths.
Topics: Animals; Humans; Oils, Volatile; Anthelmintics; Helminths; Helminthiasis; Levamisole; Drug Resistance
PubMed: 36500419
DOI: 10.3390/molecules27238327 -
Trends in Parasitology Mar 2021Anthelmintic drugs are the major line of defense against parasitic nematode infections, but the arsenal is limited and resistance threatens sustained efficacy of the... (Review)
Review
Anthelmintic drugs are the major line of defense against parasitic nematode infections, but the arsenal is limited and resistance threatens sustained efficacy of the available drugs. Discoveries of the modes of action of these drugs and mechanisms of resistance have predominantly come from studies of a related nonparasitic nematode species, Caenorhabditis elegans, and the parasitic nematode Haemonchus contortus. Here, we discuss how our understanding of anthelmintic resistance and modes of action came from the interplay of results from each of these species. We argue that this 'cycle of discovery', where results from one species inform the design of experiments in the other, can use the complementary strengths of both to understand anthelmintic modes of action and mechanisms of resistance.
Topics: Animals; Anthelmintics; Caenorhabditis elegans; Drug Resistance; Haemonchus; Nematoda; Nematode Infections; Research
PubMed: 33317926
DOI: 10.1016/j.pt.2020.11.008 -
International Journal For Parasitology.... Aug 2019Anthelmintic resistance is a threat to global food security. In order to alleviate the selection pressure for resistance and maintain drug efficacy, management... (Review)
Review
Anthelmintic resistance is a threat to global food security. In order to alleviate the selection pressure for resistance and maintain drug efficacy, management strategies increasingly aim to preserve a proportion of the parasite population in 'refugia', unexposed to treatment. While persuasive in its logic, and widely advocated as best practice, evidence for the ability of refugia-based approaches to slow the development of drug resistance in parasitic helminths is currently limited. Moreover, the conditions needed for refugia to work, or how transferable those are between parasite-host systems, are not known. This review, born of an international workshop, seeks to deconstruct the concept of refugia and examine its assumptions and applicability in different situations. We conclude that factors potentially important to refugia, such as the fitness cost of drug resistance, the degree of mixing between parasite sub-populations selected through treatment or not, and the impact of parasite life-history, genetics and environment on the population dynamics of resistance, vary widely between systems. The success of attempts to generate refugia to limit anthelmintic drug resistance are therefore likely to be highly dependent on the system in hand. Additional research is needed on the concept of refugia and the underlying principles for its application across systems, as well as empirical studies within systems that prove and optimise its usefulness.
Topics: Animals; Anthelmintics; Drug Resistance; Helminthiasis; Helminths; Humans; Refugium
PubMed: 31125837
DOI: 10.1016/j.ijpddr.2019.05.001 -
International Journal For Parasitology.... Dec 2020For more than four decades, the free-living nematode Caenorhabditis elegans has been extensively used in anthelmintic research. Classic genetic screens and heterologous... (Review)
Review
For more than four decades, the free-living nematode Caenorhabditis elegans has been extensively used in anthelmintic research. Classic genetic screens and heterologous expression in the C. elegans model enormously contributed to the identification and characterization of molecular targets of all major anthelmintic drug classes. Although these findings provided substantial insights into common anthelmintic mechanisms, a breakthrough in the treatment and control of parasitic nematodes is still not in sight. Instead, we are facing increasing evidence that the enormous diversity within the phylum Nematoda cannot be recapitulated by any single free-living or parasitic species and the development of novel broad-spectrum anthelmintics is not be a simple goal. In the present review, we summarize certain milestones and challenges of the C. elegans model with focus on drug target identification, anthelmintic drug discovery and identification of resistance mechanisms. Furthermore, we present new perspectives and strategies on how current progress in C. elegans research will support future anthelmintic research.
Topics: Animals; Anthelmintics; Caenorhabditis elegans; Drug Discovery; Nematoda
PubMed: 33249235
DOI: 10.1016/j.ijpddr.2020.09.005 -
Parasitology Jul 2020Helminth parasitology is an important discipline, which poses often unique technical challenges. One challenge is that helminth parasites, particularly those in humans,... (Review)
Review
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.
Topics: Animals; Anthelmintics; CRISPR-Cas Systems; Drug Resistance; Genome, Helminth; Genomics; Helminthiasis; Helminths; Humans; Parasitology; Pathology, Molecular; Proteomics; RNA Interference; Transcriptome
PubMed: 32252832
DOI: 10.1017/S0031182020000591 -
The Lancet. Microbe Feb 2022
Topics: Anthelmintics; Female; Helminthiasis; Humans
PubMed: 35544044
DOI: 10.1016/S2666-5247(22)00008-8