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Helminths
Terms modified by Helminths Selected AbstractsHelminths, allergic disorders and IgE-mediated immune responses: Where do we stand?EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2007Klaus Abstract Th2 responses induced by allergens or helminths share many common features. However, allergen-specific IgE can almost always be detected in atopic patients, whereas helminth-specific IgE is often not detectable and anaphylaxis often occurs in atopy but not helminth infections. This may be due to T regulatory responses induced by the helminths or the lack of helminth-specific IgE. Alternatively non-specific IgE induced by the helminths may protect from mast cell or basophil degranulation by saturating IgE binding sites. Both of these mechanisms have been implicated to be involved in helminth-induced protection from allergic responses. An article in the current issue of the European Journal of Immunology describes the generation of an anti- Nippostrongylus brasiliensis -specific IgE antibody which was used to identify a novel N. brasiliensis antigen (Nb-Ag1). The authors demonstrated that Nb-Ag1 specific IgE could only be detected for a short period of time during infection, and that these levels were sufficient to prime mast cells thereby leading to active cutaneous anaphylaxis after the application of Nb-Ag1. This is the first report clearly showing that a low level of helminth-specific IgE, transiently produced, is able to induce mast cell degranulation in the presence of large amounts of polyclonal IgE. See accompanying article: http://dx.doi/10.1002/eji.200737135 [source] WHEN SHOULD A TROPHICALLY TRANSMITTED PARASITE MANIPULATE ITS HOST?EVOLUTION, Issue 2 2009Geoffrey A. Parker We investigate evolution of two categories of adaptive host manipulation by trophically transmitted helminths: (1) predation suppression decreases the host's mortality before the helminth is capable of establishing in its next host; (2) predation enhancement increases the existing host's mortality after it can establish in its next host. If all parasite mortality is purely random (time-independent), enhancement must increase predation by the next host sufficiently more (depending on manipulative costs) than it increases the average for all forms of host mortality; thus if host and parasite die only through random predation, manipulation must increase the "right" predation more than the "wrong" predation. But if almost all parasites die in their intermediate host through reaching the end of a fixed life span, enhancement can evolve if it increases the right predation, regardless of how much it attracts wrong predators. Although enhancement is always most favorable when it targets the right host, suppression aids survival to the time when establishment in the next host is possible: it is most favorable if it reduces all aspects of host (and hence parasite) mortality. If constrained to have selective effects, suppression should reduce the commonest form of mortality. [source] Associations Between Helicobacter pylori Infection, Co-Morbid Infections, Gastrointestinal Symptoms, and Circulating Cytokines in African ChildrenHELICOBACTER, Issue 2 2010Sarah Cherian Abstract Background:, Refugee children have complex medical needs and often have multiple infections. The relationship between infection, gastrointestinal symptoms, and systemic inflammation is poorly understood. We investigated these parameters in refugee children with a high prevalence of Helicobacter pylori, helminth, and malaria infection. Materials and Methods:, African refugee children were recruited at resettlement health screening. Data were collected on demography, gastrointestinal symptoms, co-morbid infection, and serum for peripheral cytokine levels. Helicobacter pylori infection was diagnosed by a fecal-based immunoassay. Results:, Data from 163 children were analyzed, of which 84.0% were positive for H. pylori. Infected children were significantly older (9.2 years ± 3.7 vs 7.1 years ± 3.9, p = .01). Half the cohort (84/163, 51.5%) described gastrointestinal symptoms but these were not strongly associated with co-morbid infections. Helicobacter pylori -infected children had significantly lower circulating log-interleukin-8 (IL-8) (odds ratio 0.61, 95% confidence interval (CI) 0.40, 0.94, p = .025). Helminth infections were common (75/163, 46%) and associated with elevated log-IL-5 (,: 0.42, 95% CI 0.077, 0.76). Children with malaria (15/163, 9.2%) had elevated log-tumor necrosis factor-, (TNF,) and log-IL-10 (,: 0.67, 95% CI 0.34, 1.0 and ,: 1.3, 95% CI 0.67, 1.9, respectively). IL-10 : IL-12 ratios were increased in H. pylori- infected children with malaria or helminth infections. Symptoms were generally not associated with levels of circulating peripheral cytokines irrespective of co-morbid infection diagnosis. Conclusions:, There is a high prevalence of asymptomatic H. pylori infection in recently resettled African refugee children. Gastrointestinal symptoms were not predictive of H. pylori nor of helminth infections. Serum cytokines, particularly IL-5, IL-10, and TNF,, were significantly elevated in children with malaria and helminth infections but not in those with H. pylori infection. [source] Gastrointestinal parasites of the grasscutter (Thryonomys swinderianus, Temminck 1827) on the Accra Plains of GhanaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009Theodora Kankam Abstract The gastrointestinal parasites of the grasscutter were investigated between 1996 and 2006 using 180 grasscutters from the Accra Plains. The aim of the study was to develop strategies for the control of the parasites under captive management. The gastrointestinal tracts of the animals were examined for the presence of both helminth and protozoan parasites with the aid of a hand lens, the direct smear and Willis Flotation techniques. In all, fourteen species of helminths were found including twelve nematodes and two cestodes. Trichuris muris was the most common nematode encountered, whilst Hepatocola hepatica was the least commonly encountered nematode. Three genera of protozoans, viz, Trichomonas spp, Giardia spp and Eimeria spp were also encountered, with Giardia spp and Trichomonas spp being reported for the first time in the grasscutter. Eimeria spp were the most prevalent protozoa. The widespread occurrence of protozoal and helminthic parasites in the grasscutter suggests that routine treatment of grasscutters with coccidiostats, anti-flagellates and anthelminthics such as dimetridazole and albendazole may contribute significantly to improve productivity of animals and reduce the pressure on wild populations. Résumé Les parasites gastro-intestinaux de l'aulacode ont étéétudiés entre 1996 et 2006 sur 180 animaux des plaines d'Accra. Le but de l'étude était de mettre au point des stratégies pour le contrôle des parasites en captivité. Le tractus gastro-intestinal des animaux fut examiné pour détecter la présence d'helminthes et de protozoaires parasites au moyen d'une lentille à main, par prélèvement direct et par la technique de flottaison de Willis. En tout, on a trouvé 14 espèces d'helminthes, y compris 12 nématodes et deux cestodes. Trichuris murisétait le nématode le plus commun tandis que Hepatocola hepaticaétait le nématode le moins observé. Trois genres de protozoaires, c.-à-d. Trichomonas spp, Giardia spp et Eimeriaspp furent aussi observés, Giardia spp et Trichomonas spp étant rapportés pour la première fois chez l'aulacode. Eimeria spp était le protozoaire le plus répandu. La large présence de protozoaires et d'helminthes parasites chez l'aulacode suggère que le traitement de routine des aulacodes avec des coccidiostats, des antiflagellés et des antihelmintiques tels que le dimétridazole et l'albendazole peut contribuer significativement à améliorer la productivité des animaux et à réduire la pression sur les populations sauvages. [source] Regulatory T Cells in children with intestinal parasite infectionPARASITE IMMUNOLOGY, Issue 10 2009M. H. GARCÍA-HERNÁNDEZ Summary Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4+ CD25high and CD4+ Foxp3+ cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3+ CD69+, CD4+ CTLA-4+, and CD8+ CD28, T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3+ CD69+, CD4+ CTLA-4+ and CD8+ CD28, lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children. [source] ORIGINAL ARTICLE: Chronic urticaria is associated with a differential helminth,arthropod-related atopy phenotypeTHE JOURNAL OF DERMATOLOGY, Issue 9 2010Alvaro DASCHNER Abstract The relationship between atopic sensitization and chronic urticaria is still controversial. In this study, we aimed to compare the prevalence of aeroallergen sensitization in chronic urticaria patients with (CU/As+) and without (CU/As,) sensitization against Anisakis simplex. Forty-nine CU/As+ and 80 CU/As, patients were studied and skin prick tests (SPT) were performed against aeroallergens. We assessed sensitization in a subgroup of patients with allergic rhinoconjunctivitis and/or bronchial asthma (RCBA) and compared the prevalence with a control group of 522 non-urticaria patients with RCBA. Forty-five percent of CU/As, and 60.4% of CU/As+ patients displayed positive SPT to at least one aeroallergen. CU/As+ patients had a higher prevalence of sensitization against pollen, mould or dander (PMD) (52.2% vs 29.1%, P < 0.01), whereas the prevalence of house dust mite (HDM) sensitization was not statistically different (26.3% in CU/As, and 36.7% in CU/As+). However, in chronic urticaria patients with RCBA, 53.8% of CU/As, and 57.9% of CU/As+ patients differed in the prevalence of HDM sensitization compared to the control group (33.5%, P = 0.03), whereas no difference could be stated for PMD sensitization. Compared to RCBA patients, both CU/As+ and CU/As, patients have a higher clinically relevant sensitization rate against HDM, thus displaying a differential atopy phenotype. [source] X-ray structure of glutathione S -transferase from Schistosoma japonicum in a new crystal form reveals flexibility of the substrate-binding siteACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2005Arne Christian Rufer The crystal structure of the 26,kDa glutathione S -transferase from Schistosoma japonicum (SjGST) was determined at 3,Å resolution in the new space group P212121. The structure of orthorhombic SjGST reveals unique features of the ligand-binding site and dimer interface when compared with previously reported structures. SjGST is recognized as the major detoxification enzyme of S. japonicum, a pathogenic helminth causing schistosomiasis. As resistance against the established inhibitor of SjGST, praziquantel, has been reported these results might prove to be valuable for the development of novel drugs. [source] Gross anatomy of the musculature and a new description of the reproductive system of Tanaisia bragai and Tanaisia inopina (Trematoda: Eucotylidae) analysed by confocal laser scanning microscopyACTA ZOOLOGICA, Issue 2 2010Sthefane D'ávila Abstract D'ávila, S., Manso, P. P. A., Bessa, E. C. A., Rodrigues, M. L. A. and Dias, R. J. P. 2010. Gross anatomy of the musculature and a new description of the reproductive system of Tanaisia bragai and Tanaisia inopina (Trematoda: Eucotylidae) analysed by confocal laser scanning microscopy. ,Acta Zoologica (Stockholm) 91: 139,149 Confocal scanning laser microscopy has become an important tool to clarify the organization of the musculature and innervation, as well as the morphology of the reproductive and alimentary tract of various helminth species. The goal of this work was to describe the morphology of the reproductive system and the gross anatomy of the musculature of adults of the species Tanaisia bragai and Tanaisia inopina by means of confocal scanning laser microscopy. The helminths were found parasitizing the kidney collection ducts of Columba livia, in the municipality of Juiz de Fora, Brazil. These helminths were stained with Mayer's carmalum, mounted on permanent slides and observed through a confocal scanning laser microscope. The tomographic images showed the morphology of the organs and glands of the reproductive system, along with the general morphology of the musculature of the body wall, oral sucker, acetabulum, pharynx, intestinal caeca, oesophagus and reproductive system ducts. The present work is the first re-characterization of the reproductive tract of T. bragai and T. inopina. We also present the first description of the general morphology of the gametes and cells of the glands associated with the reproductive apparatus of these species. [source] Species richness of helminth parasites in Mexican amphibians and reptilesDIVERSITY AND DISTRIBUTIONS, Issue 4 2002Gerardo Pérez-Ponce de León Abstract. Amphibians and reptiles represent an important group of vertebrates in Mexico; on a global scale 10% of the biodiversity of these groups is found in the country, attaining extraordinarily high levels of endemism (60.7% and 53.7%, respectively). However, fewer than 20% of the known species of amphibians and reptiles in Mexico have been surveyed for helminths, so the inventory is far from complete. We assembled a data base that includes a total of 1246 records (entries) of which 460 correspond to helminths in amphibians and 786 to helminths in reptiles. In total, only 41 species of amphibians (14% of those occurring in Mexico) and only 118 species of reptiles (17% of those occurring in Mexico) have been studied for helminth parasites. From amphibians, 119 species of helminths belonging to 60 genera have been recorded, while 239 species of helminths representing 113 genera have been described from Mexican reptiles. One feature of the distribution of helminths of Mexican amphibians and reptiles is its asymmetry, as seen in representation of helminth groups, host groups and geographical range. However, such statistical asymmetry might be an artefact of sampling effort. Based on our data, we estimate that if all the herpetofauna of Mexico could be studied in the following years, approximately 827 additional species of helminths from amphibians and approximately 1403 from reptiles would be described. [source] Testing the energetic equivalence rule with helminth endoparasites of vertebratesECOLOGY LETTERS, Issue 7 2004Mario George-Nascimento Abstract As a general test of the energetic equivalence rule, we examined macroecological relationships among abundance, density and host body mass in a comparative analysis of the assemblages of trophically transmitted endoparasitic helminths of 131 species of vertebrate hosts. Both the numbers and total volume of parasites per gram of host decreased allometrically with host body mass, with slopes roughly consistent with those expected from the allometric relationship between host basal metabolic rate and body mass. From an evolutionary perspective, large body size may therefore allow hosts to escape from the deleterious effects of parasitism. [source] Chitin induces upregulation of B7-H1 on macrophages and inhibits T-cell proliferationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2010Claudia J. Wagner Abstract Chitin is a highly abundant glycopolymer, which serves as structural component in fungi, arthropods and crustaceans but is not synthesized by vertebrates. However, vertebrates express chitinases and chitinase-like proteins, some of which are induced by infection with helminths suggesting that chitinous structures may be targets of the immune system. The chitin-induced modulations of the innate and adaptive immune responses are not well understood. Here, we demonstrate that intranasal administration of OVA and chitin resulted in diminished T-cell expansion and Th2 polarization as compared with OVA administration alone. Chitin did not promote nor attenuate Th2 polarization in vitro. Chitin-exposed macrophages inhibited proliferation of CD4+ T cells in a cell,cell contact-dependent manner. Chitin induced upregulation of the inhibitory ligand B7-H1 (PD-L1) on macrophages independently of MyD88, TRIF, TLR2, TLR3, TLR4 and Stat6. Inhibition of T-cell proliferation was largely dependent on B7-H1, as the effect was not observed in cocultures with cells from B7-H1-deficient mice. [source] Mapping immune response profiles: The emerging scenario from helminth immunologyEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2007Alvaro Díaz Abstract Metazoan parasites of mammals (helminths) belong to highly divergent animal groups and yet induce a stereotypical host response: Th2-type immunity. It has long been debated whether this response benefits the host or the parasite. We review the current literature and suggest that Th2 immunity is an evolutionarily appropriate response to metazoan invaders both in terms of controlling parasites and repairing the damage they inflict. However, successful parasites induce regulatory responses, which become superimposed with, and control, Th2 responses. Beyond helminth infection, this superimposition of response profiles may be the norm: both Th1 and Th2 responses coexist with regulatory responses or, on the contrary, with the inflammatory Th17 responses. Thus, typical responses to helminth infections may differ from Th2-dominated allergic reactions in featuring not only a stronger regulatory component but also a weaker Th17 component. The similarity of immune response profiles to phylogenetically distinct helminths probably arises from mammalian evolution having hard-wired diverse worm molecules, plus tissue-damage signals, to the beneficial Th2 response, and from the convergent evolution of different helminths to elicit regulatory responses. We speculate that initiation of both Th2 and regulatory responses involves combinatorial signaling, whereby TLR-mediated signals are modulated by signals from other innate receptors, including lectins. [source] Helminths, allergic disorders and IgE-mediated immune responses: Where do we stand?EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2007Klaus Abstract Th2 responses induced by allergens or helminths share many common features. However, allergen-specific IgE can almost always be detected in atopic patients, whereas helminth-specific IgE is often not detectable and anaphylaxis often occurs in atopy but not helminth infections. This may be due to T regulatory responses induced by the helminths or the lack of helminth-specific IgE. Alternatively non-specific IgE induced by the helminths may protect from mast cell or basophil degranulation by saturating IgE binding sites. Both of these mechanisms have been implicated to be involved in helminth-induced protection from allergic responses. An article in the current issue of the European Journal of Immunology describes the generation of an anti- Nippostrongylus brasiliensis -specific IgE antibody which was used to identify a novel N. brasiliensis antigen (Nb-Ag1). The authors demonstrated that Nb-Ag1 specific IgE could only be detected for a short period of time during infection, and that these levels were sufficient to prime mast cells thereby leading to active cutaneous anaphylaxis after the application of Nb-Ag1. This is the first report clearly showing that a low level of helminth-specific IgE, transiently produced, is able to induce mast cell degranulation in the presence of large amounts of polyclonal IgE. See accompanying article: http://dx.doi/10.1002/eji.200737135 [source] WHEN SHOULD A TROPHICALLY TRANSMITTED PARASITE MANIPULATE ITS HOST?EVOLUTION, Issue 2 2009Geoffrey A. Parker We investigate evolution of two categories of adaptive host manipulation by trophically transmitted helminths: (1) predation suppression decreases the host's mortality before the helminth is capable of establishing in its next host; (2) predation enhancement increases the existing host's mortality after it can establish in its next host. If all parasite mortality is purely random (time-independent), enhancement must increase predation by the next host sufficiently more (depending on manipulative costs) than it increases the average for all forms of host mortality; thus if host and parasite die only through random predation, manipulation must increase the "right" predation more than the "wrong" predation. But if almost all parasites die in their intermediate host through reaching the end of a fixed life span, enhancement can evolve if it increases the right predation, regardless of how much it attracts wrong predators. Although enhancement is always most favorable when it targets the right host, suppression aids survival to the time when establishment in the next host is possible: it is most favorable if it reduces all aspects of host (and hence parasite) mortality. If constrained to have selective effects, suppression should reduce the commonest form of mortality. [source] A new paradigm of eosinophil granulocytes: neuroimmune interactionsEXPERIMENTAL DERMATOLOGY, Issue 9 2008Ulrike Raap Abstract:, Eosinophil granulocytes have long been regarded as potent effector cells with the potential to release an array of inflammatory mediators involved in cytotoxicity to helminths and tissue destruction in chronic inflammatory diseases such as asthma. However, it has become evident that eosinophils are also involved in regulatory mechanisms modulating local tissue immune responses. Eosinophils take part in remodelling and repair mechanisms and contribute to the localized innate and acquired immune response as well as systemic adaptive immunity. In addition, eosinophils are involved in neuroimmune interactions modulating the functional activity of peripheral nerves. Neuromediators can also modulate the functional activity of eosinophils, revealing bidirectional interactions between the two cell types. Eosinophils are tissue-resident cells and have been found in close vicinity of peripheral nerves. This review describes neuroimmune interactions between eosinophil granulocytes and peripheral nerves and highlights why eosinophils are important in allergic diseases such as asthma. [source] Parasitic worms of the central nervous system: an Australian perspectiveINTERNAL MEDICINE JOURNAL, Issue 11 2002A. J. Hughes Abstract The diagnosis and management of parasitic diseases of the central nervous system (CNS) is difficult, even for infectious diseases physicians and neurologists. Furthermore, few overviews of the spectrum of causative helminths and clinical syndromes have been published. In the present study, we review the seven most common parasitic diseases of the CNS: (i) cysticercosis, (ii) neuroschistosomiasis, (iii) paragonimiasis, (iv) angio-strongyliasis, (v) hydatid disease, (vi) sparganosis and (vii) gnathostomiasis. Major syndromes of parasitic disease of the CNS and their differential causes are discussed, including: (i) cystic lesions, (ii) enhancing granulomas (with and without creeping subcutaneous eruptions), (iii) eosinophilic meningoencephalitis and (iv) spinal cord disease. Specific risk factors that predispose to these infections are also discussed and particular attention is drawn to the situation in Australia. (Intern Med J 2002; 32: 541,553) [source] Do threatened hosts have fewer parasites?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2007A comparative study in primates Summary 1Parasites and infectious diseases have become a major concern in conservation biology, in part because they can trigger or accelerate species or population declines. Focusing on primates as a well-studied host clade, we tested whether the species richness and prevalence of parasites differed between threatened and non-threatened host species. 2We collated data on 386 species of parasites (including viruses, bacteria, protozoa, helminths and arthropods) reported to infect wild populations of 36 threatened and 81 non-threatened primate species. Analyses controlled for uneven sampling effort and host phylogeny. 3Results showed that total parasite species richness was lower among threatened primates, supporting the prediction that small, isolated host populations harbour fewer parasite species. This trend was consistent across three major parasite groups found in primates (helminths, protozoa and viruses). Counter to our predictions, patterns of parasite species richness were independent of parasite transmission mode and the degree of host specificity. 4We also examined the prevalence of selected parasite genera among primate sister-taxa that differed in their ranked threat categories, but found no significant differences in prevalence between threatened and non-threatened hosts. 5This study is the first to demonstrate differences in parasite richness relative to host threat status. Results indicate that human activities and host characteristics that increase the extinction risk of wild animal species may lead simultaneously to the loss of parasites. Lower average parasite richness in threatened host taxa also points to the need for a better understanding of the cascading effects of host biodiversity loss for affiliated parasite species. [source] Male-biased parasitism by common helminths is not explained by sex differences in body size or spleen mass of breeding cormorants Phalacrocorax auritusJOURNAL OF AVIAN BIOLOGY, Issue 3 2008Stacey A. Robinson In vertebrates, males are often more parasitised than conspecific females. This bias in parasitism might result from sex differences in parasite exposure and/or susceptibility to infection. Such information is important for testing hypotheses about allocation of resources to life histories of males and females and for testing hypotheses about factors thought to influence parasite fitness and parasite dynamics. We tested whether double-crested cormorants Phalacrocorax auritus exhibit male-biased parasitism by gut helminths. The prevalence of nematode Contracaecum spp. and trematode Drepanocaphalus spathans infections was ,90% and 39%, respectively. Cestode, primarily Paradilepis caballeroi and acanthocephalan Andracantha gravida infections were less common (<10%). Male and female cormorants did not differ in prevalence of infection by any helminth species. However, males had twice the abundance and intensity of Contracaecum spp. infections and twice the intensity of D. spathans infections than found in females. For common parasites showing male-biased parasitism, degree of parasitism was also unrelated to body size or mass in either sex. Males and females did not differ in spleen mass and spleen mass was unrelated to abundance of common parasites. Furthermore, abundance of trematodes and nematodes was not correlated. At present, male biases in parasitism by nematodes and trematodes in cormorants are independent patterns that remain unexplained, but are most likely attributable to sex differences in exposure and/or immunological differences not yet assessed. [source] The historical biogeography of co-evolution: emerging infectious diseases are evolutionary accidents waiting to happenJOURNAL OF BIOGEOGRAPHY, Issue 8 2005Daniel R. Brooks Abstract Ecological fitting refers to interspecific associations characterized by ecologically specialized, yet phylogenetically conservative, resource utilization. During periods of biotic expansion, parasites and hosts may disperse from their areas of origin. In conjunction with ecological fitting, this sets the stage for host switching without evolving novel host utilization capabilities. This is the evolutionary basis of emerging infectious diseases (EIDs). Phylogenetic analysis for comparing trees (PACT) is a method developed to delineate both general and unique historically reticulated and non-reticulated relationships among species and geographical areas, or among parasites and their hosts. PACT is based on ,Assumption 0', which states that all species and all hosts in each input phylogeny must be analysed without modification, and the final analysis must be logically consistent with all input data. Assumption 0 will be violated whenever a host or area has a reticulated history with respect to its parasites or species. PACT includes a Duplication Rule, by which hosts or areas are listed for each co-evolutionary or biogeographical event affecting them, which satisfies Assumption 0 even if there are reticulations. PACT maximizes the search for general patterns by using Ockam's Razor , duplicate only enough to satisfy Assumption 0. PACT applied to the host and geographical distributions of members of two groups of parasitic helminths infecting anthropoid primates indicates a long and continuous association with those hosts. Nonetheless, c. 30% of the host associations are due to host switching. Only one of those involves non-primate hosts, suggesting that most were constrained by resource requirements that are phylogenetically conservative among primates (ecological fitting). In addition, most of the host switches were associated with episodes of biotic expansion, also as predicted by the ecological fitting view of EIDs. [source] Richness and diversity of helminth communities in tropical freshwater fishes: empirical evidenceJOURNAL OF BIOGEOGRAPHY, Issue 4 2000Anindo Choudhury Abstract Aim Published information on the richness and diversity of helminth parasite communities in tropical freshwater fishes is reviewed in response to expectations of species-rich parasite communities in tropical regions. Location Areas covered include the tropics and some subtropical areas. In addition, the north temperate area of the nearctic zone is included for comparison. Methods Data from 159 communities in 118 species of tropical freshwater fish, summarized from 46 published studies, were used for this review. Parasite community descriptors used in the analyses included component community richness and calculated mean species richness. Data from 130 communities in 47 species of nearctic north temperate freshwater fish were summarized from 31 studies and used for comparison. Results The component helminth communities of many tropical freshwater fish are species-poor, and considerable proportions of fish from certain parts of the tropics, e.g. West African drainages, are uninfected or lightly infected. Mean helminth species richness was low and equaled or exceeded 2.0 in only 22 of 114 communities. No single group of helminths was identified as a dominant component of the fauna and species composition was variable among and within broader geographical areas. The richest enteric helminth assemblages were found in mochokid and clariid catfish with a mixed carnivorous diet, whereas algal feeders, herbivores and detritivores generally had species-poor gut helminth communities. Comparisons indicated that certain areas in the north temperate region had higher helminth species richness in fishes than areas in the tropics. Main conclusions Expectations of high species richness in helminth communities of tropical freshwater fishes are not fulfilled by the data. Direct comparisons of infracommunities and component communities in host species across widely separated phylogenetic and geographical lines are inappropriate. Examination of latitudinal differences in richness of monophyletic parasite groups or of compound communities may uncover patterns different from those found in this study. Richness of helminth communities may be ultimately determined not by the number of host species present but by the degree of divergence of host lineages and by their diversification modes. A phylogenetic framework for hosts and parasites will reveal if increased host species richness within host clades, when host speciation is accompanied by habitat or diet specialization, or both, leads to lower helminth diversity in host species by fragmentation of a core helminth fauna characteristic or specific of the larger host clade. This pattern may be analysed in the context of cospeciation and acquisition from other unrelated hosts (host-sharing or host-switching). [source] Gastrointestinal parasites of the grasscutter (Thryonomys swinderianus, Temminck 1827) on the Accra Plains of GhanaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009Theodora Kankam Abstract The gastrointestinal parasites of the grasscutter were investigated between 1996 and 2006 using 180 grasscutters from the Accra Plains. The aim of the study was to develop strategies for the control of the parasites under captive management. The gastrointestinal tracts of the animals were examined for the presence of both helminth and protozoan parasites with the aid of a hand lens, the direct smear and Willis Flotation techniques. In all, fourteen species of helminths were found including twelve nematodes and two cestodes. Trichuris muris was the most common nematode encountered, whilst Hepatocola hepatica was the least commonly encountered nematode. Three genera of protozoans, viz, Trichomonas spp, Giardia spp and Eimeria spp were also encountered, with Giardia spp and Trichomonas spp being reported for the first time in the grasscutter. Eimeria spp were the most prevalent protozoa. The widespread occurrence of protozoal and helminthic parasites in the grasscutter suggests that routine treatment of grasscutters with coccidiostats, anti-flagellates and anthelminthics such as dimetridazole and albendazole may contribute significantly to improve productivity of animals and reduce the pressure on wild populations. Résumé Les parasites gastro-intestinaux de l'aulacode ont étéétudiés entre 1996 et 2006 sur 180 animaux des plaines d'Accra. Le but de l'étude était de mettre au point des stratégies pour le contrôle des parasites en captivité. Le tractus gastro-intestinal des animaux fut examiné pour détecter la présence d'helminthes et de protozoaires parasites au moyen d'une lentille à main, par prélèvement direct et par la technique de flottaison de Willis. En tout, on a trouvé 14 espèces d'helminthes, y compris 12 nématodes et deux cestodes. Trichuris murisétait le nématode le plus commun tandis que Hepatocola hepaticaétait le nématode le moins observé. Trois genres de protozoaires, c.-à-d. Trichomonas spp, Giardia spp et Eimeriaspp furent aussi observés, Giardia spp et Trichomonas spp étant rapportés pour la première fois chez l'aulacode. Eimeria spp était le protozoaire le plus répandu. La large présence de protozoaires et d'helminthes parasites chez l'aulacode suggère que le traitement de routine des aulacodes avec des coccidiostats, des antiflagellés et des antihelmintiques tels que le dimétridazole et l'albendazole peut contribuer significativement à améliorer la productivité des animaux et à réduire la pression sur les populations sauvages. [source] Cloning and heterologous expression of the ovine (Ovis aries) P-glycoprotein (Mdr1) in Madin,Darby canine kidney (MDCK) cellsJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2010D. ZAHNER Zahner, D., Alber, J., Petzinger, E. Cloning and heterologous expression of the ovine (Ovis aries) P-glycoprotein (Mdr1) in Madin,Darby canine kidney (MDCK) cells. J. vet. Pharmacol. Therap.33, 304,311. P-glycoprotein (P-gp) plays a crucial role in the multidrug resistance of pathogenic helminths in sheep (Ovis aries) as well as in antiparasitic drug pharmacokinetics in the host. We cloned sheep P-gp cDNA and expressed it stably in Madin,Darby canine kidney (MDCK) cells. The open reading frame consists of 3858 nucleotides coding for a 1285 amino acids containing protein. The sequence shows high homology to the orthologs of other mammalian species, especially cattle. Both ruminant DNA sequences show a 9 bp insertion that is lacking in all other investigated sequences. Expressed in MDCK cells, the protein displays a size of 170 kDa on Western analysis. Transfection of MDCK cells with sheep P-gp resulted in 10- to 50-fold resistance to the cytotoxic P-gp substrates colchicin and daunorubicin, and in reduced digoxin accumulation. [source] The role of parasitic infections in atopic diseases in rural schoolchildrenALLERGY, Issue 8 2006B. Karadag Background:, There is increasing evidence that the farming environment has a protective effect as regards allergic diseases. Exposure to animal parasites, particularly helminth infections, is common in the farming environment. However, the role of helminths in this environment is not well determined to date. Methods:, This analysis focuses on 613 children 6,13 years of age from rural areas of Austria, Germany and Switzerland, who took part in the Allergy and Endotoxin (ALEX) study. Allergic diseases and farming characteristics were assessed by a standardized questionnaire and as a crude measure of possible exposure to helminths, IgG antibodies to Ascaris lumbricoides were measured. Results:, Exposure to nematodes, as determined by the levels of antibody to A. lumbricoides, was more frequent among farmers' children than non-farmers' children (39.8%vs 31.1%, P = 0.03). This positive serology was found to be significantly associated with high total IgE levels [odds ratio (OR) = 3.05, 95% confidence interval (CI) = 1.81,5.12] and eosinophilia (OR = 2.84, 95% CI = 1.66,4.84). However, no association between anti-nematode serology and the prevalences of asthma, wheeze, hay fever or atopy was found. A weak association for atopy was observed after adjustment for total IgE. Conclusion:, Immunoglobulin G antibodies to A. lumbricoides, as a crude measure of possible exposure to helminths, did not indicate any protective effect against allergic diseases in this population. Although farmers' children had increased antibody levels reactive to helminth parasites indicating exposure, this did not explain the protective effect of farming against atopic diseases. [source] The gut, immunoregulation and micro-organisms from man's evolutionary pastNUTRITION BULLETIN, Issue 2 2010G. A. W. Rook Summary Man has moved rapidly from the hunter-gatherer environment to the living conditions of the rich industrialised countries. The hygiene hypothesis suggests that the resulting changed and reduced pattern of exposure to certain critical micro-organisms, mostly derived from mud, animals and faeces, has led to disordered regulation of the immune system and, hence, to increases in chronic inflammatory disorders such as allergies, inflammatory bowel diseases and autoimmunity. Epidemiology, backed up by laboratory models, indicates that the relevant organisms are those that have very long associations with the mammalian immune system, traceable back to the Palaeolithic or earlier. Often, these organisms have been present as commensals (notably in the intestinal microbiota), environmental ,pseudocommensals', sub-clinical infections or asymptomatic carrier states, and the mammalian immune system is in a state of ,evolved dependence' on their continued presence. Several of these ,Old Friends', often operating primarily in the gut, act as modulators of dendritic cells and T cells, leading to the establishment of immunoregulatory circuits. Clinical trials are in progress to test living helminths (Trichuris suis and Necator americanus) in allergies, inflammatory bowel disease and multiple sclerosis. We can anticipate rapid increases in the use of these and other organisms or their components in novel types of therapy with applications in several branches of medicine. Probiotics tested in clinical trials targeting chronic inflammatory disorders have so far given unconvincing results, but if strains for these indications are selected on the basis of their ability to induce immunoregulation, and not merely imposed by companies that have intellectual property rights, we can anticipate rapid progress. [source] Regulatory T Cells in children with intestinal parasite infectionPARASITE IMMUNOLOGY, Issue 10 2009M. H. GARCÍA-HERNÁNDEZ Summary Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4+ CD25high and CD4+ Foxp3+ cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3+ CD69+, CD4+ CTLA-4+, and CD8+ CD28, T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3+ CD69+, CD4+ CTLA-4+ and CD8+ CD28, lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children. [source] Expression of helminth genes in Leishmania: an experimental transfection system to test immunological functionPARASITE IMMUNOLOGY, Issue 4 2008R. M. MAIZELS SUMMARY Functional analysis of genes from parasitic helminths requires, at the present time, heterologous expression. We have adapted the well-characterized system of transfection in Leishmania protozoal parasites, as a means of analysing the effect of single filarial genes on the mammalian immune system. For example, testing the function of the Brugia malayi abundant larval transcript (ALT) gene-transfected Leishmania mexicana were found to be significantly more virulent in macrophages in vitro. The course of infection in vivo is also aggravated by expression of the ALT gene. Examples are also given of transgenes which reduced in vitro growth within macrophages, as well as others which exert no effect on the protozoal parasitism. Thus, Leishmania transfection provides a tractable system to analyse helminth gene function within the context of the host immune system. [source] Immune modulation by helminthic infections: worms and viral infectionsPARASITE IMMUNOLOGY, Issue 10 2006S. M. KAMAL SUMMARY Helminthic infections occur worldwide, especially in developing countries. About one-quarter of the world's population, 1·5 billion, are infected with one or more of the major soil-transmitted helminths, including hookworms, ascarids, and whipworms. Schistosomes infect more than 200 million people worldwide with 600 million at risk in 74 countries. The interaction between helminths and the host's immune system provokes particular immunomodulatory and immunoregulatory mechanisms that ensure their survival in the host for years. However, these changes might impair the immunological response to bystander bacterial, viral, and protozoal pathogens and to vaccination. Modulation of the immune system by infection with helminthic parasites is proposed to reduce the levels of allergic responses and to protect against inflammatory bowel disease. In this review, we summarize the immunological milieu associated with helminthic infections and its impact on viral infections, mainly hepatitis B virus, hepatitis C virus, and human immunodeficiency virus in humans and experimental animals. [source] Echinococcus multilocularis metacestode extract triggers human basophils to release interleukin-4PARASITE IMMUNOLOGY, Issue 10 2004E. Aumüller SUMMARY Infections with parasitic helminths are associated with a T helper 2 (Th2) immune response and IgE production. The underlying mechanism, however, is only partially understood. Recently we have isolated a protein from extracts of Schistosoma mansoni eggs that triggers human basophils from non-sensitized donors to release interleukin-4 (IL-4), the key cytokine of a Th2 response. We called this protein IPSE (for IL-4-inducing principle from Schistosoma mansoni eggs). Supposing that IPSE-like IL-4-inducing activities might be a general principle shared among different helminth species, we investigated extracts from the cestode E. multilocularis for its effect on human basophils. Our results showed that extracts from metacestodes of E. multilocularis cause basophil degranulation, as well as the secretion of histamine, IL-4 and IL-13, in a dose-dependent manner. IgE stripping and resensitization of basophils indicated that the mechanism of IL-4 induction requires the presence of IgE on the cells. Since analogous properties have been demonstrated earlier for IPSE, we think that S. mansoni and E. multilocularis may induce a Th2 response in their hosts via a related mechanism, namely, by the induction of IL-4 release from basophils. [source] Worms and malaria: noisy nuisances and silent benefitsPARASITE IMMUNOLOGY, Issue 7 2002Mathieu Nacher Summary The burden of malaria mortality has been a major evolutionary influence on human immunity. The selection of the most successful immune responses against malaria has been in populations concomitantly infected by intestinal helminths. Animal models have shown that coinfections with helminths and protozoa in the same host elicit a range of antagonist and synergistic interactions. Recent findings suggest similar interactions take place between helminths, Plasmodium falciparum and humans. However, as the threat of HIV and tuberculosis becomes a major selective force, what used to be a successful ecological system may now prove detrimental. Nevertheless, the understanding of the ecological forces at play may expose new intervention targets for malaria control, and give a new perspective on our shortcomings against the deadliest of human parasites. [source] Ascaris lumbricoides infection is associated with protection from cerebral malariaPARASITE IMMUNOLOGY, Issue 3 2000Mathieu Nacher Following reports of increased IgE in severe malaria and hypothesizing that helminth coinfections could modify its outcome, we conducted a retrospective case,control study to establish whether helminths affect the evolution of Plasmodium falciparum malaria. Some 182 severe cases, 315 mild controls and 40 controls with circulating schizonts were examined for intestinal helminths. Comparing cerebral malaria with mild controls, Ascaris lumbricoides was associated with a protective adjusted odds ratio (OR) of 0.58 (0.32,1.03) P = 0.06, for coinfection with Ascaris and Necator americanus, OR = 0.39 (0.17,0.88) P = 0.02. Protection followed a dose,effect trend (P = 0.008). When comparing cerebral malaria cases and controls with circulating schizonts the OR was 0.25 (0.009,0.67) P = 0.006. We hypothesized that Ascaris infected patients may have had decreased cyto-adherence, possibly through endothelial cell receptor downregulation and/or decreased splenic clearance leading to the absence of selection of virulent P. falciparum strains. IgE-anti-IgE immune complexes resulting from helminth preinfection may have an important role in influencing clinical presentation of severe malaria, and in establishing malaria tolerance, through the CD23/NO pathway. [source] | |||||||||||||||||||||||||||||||||||||