Advances in Parasitology最新文献

The use of chemotherapeutic drugs is the main resource against clinical giardiasis due to the lack of approved vaccines. Resistance of G. duodenalis to the most used drugs to treat giardiasis, metronidazole and albendazole, is a clinical issue of growing concern and yet unknown impact, respectively. In the search of new drugs, the completion of the Giardia genome project and the use of biochemical, molecular and bioinformatics tools allowed the identification of ligands/inhibitors for about one tenth of ≈150 potential drug targets in this parasite. Further, the synthesis of second generation nitroimidazoles and benzimidazoles along with high-throughput technologies have allowed not only to define overall mechanisms of resistance to metronidazole but to screen libraries of repurposed drugs and new pharmacophores, thereby increasing the known arsenal of anti-giardial compounds to some hundreds, with most demonstrating activity against metronidazole or albendazole-resistant Giardia. In particular, cysteine-modifying agents which include omeprazole, disulfiram, allicin and auranofin outstand due to their pleiotropic activity based on the extensive repertoire of thiol-containing proteins and the microaerophilic metabolism of this parasite. Other promising agents derived from higher organisms including phytochemicals, lactoferrin and propolis as well as probiotic bacteria/fungi have also demonstrated significant potential for therapeutic and prophylactic purposes in giardiasis. In this context the present chapter offers a comprehensive review of the current knowledge, including commonly prescribed drugs, causes of therapeutic failures, drug resistance mechanisms, strategies for the discovery of new agents and alternative drug therapies.

The toxocariasis incidence in Russia is relatively low (1.8 cases per 100,000 individuals) and the parasite is not a major healthcare concern. However, the proportion of primary hosts testing positive for the parasite is high and varies between 3% and 100% in dogs (on average 33%), and between 6% and 52% in cats. Higher prevalence was observed in Volga, Urals and Siberia regions. Levels of contamination of soil, children's playgrounds and sandboxes is also high, with up to 100% contamination rates determined in some studies, but more commonly prevalence of contamination around 40% was reported. There is a pronounced seasonality in the prevalence of Toxocara in primary hosts and the soil, with peaks in the summer and autumn. Most likely, a lack of permissive conditions for the development of eggs in the winter determines observed seasonal patterns, which are different than those observed in most other countries. Toxocara eggs were found in 4-10% of vegetables and greenery samples tested, suggesting that they can contribute to the transmission of Toxocara.

Toxocariasis is one of the most neglected worldwide zoonoses that is caused by larval nematode parasites of the genus Toxocara, Toxocara canis, and to a lesser extent, Toxocara cati, whose migration mechanism is still largely unknown. Fortunately, some advanced tools have been employed, such as genomics, transcriptomics, and proteomics, to better understand the molecular biology and regulatory mechanisms of Toxocara. Using genomics and transcriptomics, we can identify a large number of genes that participate in the development of Toxocara and the interaction of parasites and their hosts and can predict the functions of unknown genes by comparing them with other relevant species. Using proteomics, we can identify somatic proteins and excretory and secretory (ES) proteins that perform specific biological functions in tissue degradation, pathogen invasion, immune evasion or modulation. These "omics" techniques also can contribute enormously to the development of new drugs, vaccines and diagnostic tools for toxocariasis. In a word, by utilizing "omics", we can better understand the Toxocara and toxocariasis. In this review, we summarized the representative achievements in Toxocara and the interaction between Toxocara spp. and their hosts based on expressed sequence tags (ESTs), microarray gene expression, next-generation sequencing (NGS) technologies and liquid chromatography-tandem mass spectrometry (LC-MS/MS), hoping to better understand the molecular biology of Toxocara, and contribute to new progress in the application areas of new drugs, vaccines and diagnostic tool for toxocariasis in the future.

Overall incidence of toxocariasis in Russia is low and varies between 1.6 and 2.7 per 100,000, while in several hyper-endemic regions, such as Altay, Kurgan, Perm and Udmurtia, it reaches 43 per 100,000. The seroprevalence of toxocariasis in published references was on average 16% and varied across the regions of Russia from negligible in North Siberia to 40% in southern regions of West Siberia. Seroprevalence in adults in five regions of Russia identified in this study was on average 20%, and varied from 3% in Yakutia (north of East Siberia) to 36% in Rostov-on-Don, South Russia. There was no correlation between seroprevalence and reported incidence of toxocariasis; however, the pattern of seroprevalence variation could be linked to Toxocara prevalence in dogs. Toxocariasis seroprevalence has more than doubled over the last 20 years. Diagnostic antibody titres (1:800 or more) were found in 3.6% of sera, suggesting about five million of acute Toxocara invasions per year.

In Mexico, toxocariasis, like some other parasitosis in humans, is not a disease of conventional surveillance or immediate notification. Seroprevalence studies are scarce, six dealing with paediatric populations and eight dealing with adults; the reports were only from four states in Mexico. There were 1596 children, and the seroprevalence was 13.8%. In the case of adults, there were 1827 subjects, and seroprevalence was 4.7%. There is a significant positive association between seroprevalence and the paediatric population P<0.0001 (OR, 3.285; 95% CI, 2.541-4.279). It is advisable to perform competitive ELISAs and add another diagnostic test, such as Western blot or the detection of circulating antigens to reduce diagnostic uncertainty. This neglected parasitosis can be confused with retinoblastoma. Therefore, there is a risk of ocular enucleation. It is necessary to sensitise the authorities of the Ministry of Health and decision-makers, to provide economic support for epidemiological surveillance of this zoonotic parasite.

In the past two decades, significant progress has been made in the sequencing, assembly, annotation and analyses of genomes and transcriptomes of parasitic worms of socioeconomic importance. This progress has somewhat improved our knowledge and understanding of these pathogens at the molecular level. However, compared with the free-living nematode Caenorhabditis elegans, the areas of functional genomics, transcriptomics, proteomics and metabolomics of parasitic nematodes are still in their infancy, and there are major gaps in our knowledge and understanding of the molecular biology of parasitic nematodes. The information on signalling molecules, molecular pathways and microRNAs (miRNAs) that are known to be involved in developmental processes in C. elegans and the availability of some molecular resources (draft genomes, transcriptomes and some proteomes) for selected parasitic nematodes provide a basis to start exploring the developmental biology of parasitic nematodes. Indeed, some studies have identified molecules and pathways that might associate with developmental processes in related, parasitic nematodes, such as Haemonchus contortus (barber's pole worm). However, detailed information is often scant and 'omics resources are limited, preventing a proper integration of 'omic data sets and comprehensive analyses. Moreover, little is known about the functional roles of pheromones, hormones, signalling pathways and post-transcriptional/post-translational regulations in the development of key parasitic nematodes throughout their entire life cycles. Although C. elegans is an excellent model to assist molecular studies of parasitic nematodes, its use is limited when it comes to explorations of processes that are specific to parasitism within host animals. A deep understanding of parasitic nematodes, such as H. contortus, requires substantially enhanced resources and the use of integrative 'omics approaches for analyses. The improved genome and well-established in vitro larval culture system for H. contortus provide unprecedented opportunities for comprehensive studies of the transcriptomes (mRNA and miRNA), proteomes (somatic, excretory/secretory and phosphorylated proteins) and lipidomes (e.g., polar and neutral lipids) of this nematode. Such resources should enable in-depth explorations of its developmental biology at a level, not previously possible. The main aims of this review are (i) to provide a background on the development of nematodes, with a particular emphasis on the molecular aspects involved in the dauer formation and exit in C. elegans; (ii) to critically appraise the current state of knowledge of the developmental biology of parasitic nematodes and identify key knowledge gaps; (iii) to cover salient aspects of H. contortus, with a focus on the recent advances in genomics, transcriptomics, proteomics and lipidomics as well as in vitro culturing systems; (iv) to review recent advances in our knowledge and understanding of the mol

Toxocariosis is an important neglected tropical helminth disease of zoonotic significance for which canids are the definitive hosts. Dogs are also considered the sentinel host for the occurrence of T. canis infections in humans. Therefore, understanding its prevalence in canine population is imperative for any effective disease control in humans. A comprehensive review of literature on the prevalence of T. canis in canids was lacking from the Indian subcontinent which necessitated our efforts to compile available data published on this topic. Data on prevalence, incidence and occurrence of this helminths in canids were presented in this review as tabular format for easy comprehension. Moreover, the data were categorized based on the region where the studies were conducted with an aim to understand the spatial distribution of this parasite in the subcontinent. Factors influencing the regional prevalence/occurrence of T. canis such as type of canids (stray or pet), age, sex, breed, season and the choice of analytical methods were also discussed. In addition, data on the prevalence of T. canis in environmental samples and in zoo canids were also compiled and presented. We anticipate such an exhaustive review of literature available mostly in the journals published from the subcontinent would become a point source of information necessary for prioritizing future surveillance efforts in this region and for making informed policy decision to control this zoonotic helminth infection.