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Helminth Parasites (helminth + parasite)
Selected AbstractsPotential spread of introduced black rat (Rattus rattus) parasites to endemic deer mice (Peromyscus maniculatus) on the California Channel IslandsDIVERSITY AND DISTRIBUTIONS, Issue 6 2006Katherine F. Smith ABSTRACT Introduced species have the potential to outperform natives in two primary ways: via increased rates of predation and competition, and via the introduction of new parasites against which native species often lack effective immune defences. To assess the extent to which invasive species' parasites spread to native hosts, we compared the composition of helminth parasites found in introduced black rat (Rattus rattus) and endemic deer mouse (Peromyscus maniculatus) populations on a subset of the California Channel Islands. Results suggest that the whipworm, Trichuris muris, may have spread from introduced black rats to endemic island deer mice and has continued to thrive in one island population where rats were recently eradicated. These results yield two important conservation messages: (1) although the parasites introduced with invasive species may be few, they should not be ignored as they can spread to native species, and (2) introduced parasites have the potential to remain in a system even after their founding host is extirpated. These findings underscore the importance of parasitological surveys in invasive species research and baseline data for ecosystems where exotic species are likely to invade. [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] Spatial variation in population density across the geographical range in helminth parasites of yellow perch Perca flavescensECOGRAPHY, Issue 5 2007Robert Poulin The abundance of a species is not constant across its geographical range; it has often been assumed to decrease from the centre of a species' range toward its margins. The central assumption of this "favourable centre" model is tested for the first time with parasites, using different species of helminth parasites exploiting fish as definitive hosts. Data on prevalence (percentage of hosts that are infected) and abundance (mean no. parasites per host) were compiled for 8 helminth species occurring in 23 populations of yellow perch Perca flavescens, from continental North America. For each parasite species, correlations were computed between latitude and both local prevalence and abundance values. In addition, the relationships between the relative prevalence or abundance in one locality and the distance between that locality and the one where the maximum value was reported, were assessed separately for each species to determine whether abundance tends to decrease away from the presumed centre of the range, where it peaks. For both the cestode Proteocephalus pearsei and the acanthocephalan Leptorhynchoides thecatus, there was a positive relationship between prevalence or abundance and the latitude of the sampled population. There was also a significant negative relationship between relative prevalence and the distance from the locality showing the maximum value in P. pearsei, but no such pattern was observed for the other 7 parasite species. Since this single significant decrease in prevalence with increasing distance from the peak value may be confounded by a latitudinal gradient, it appears that the distribution of abundance in parasites of perch does not follow the favourable centre model. This means that the environmental variables affecting the density of parasites (host availability, abiotic conditions) do not show pronounced spatial autocorrelation, with nearby sites not necessarily providing more similar conditions for the growth of parasite populations than distant sites. [source] Sex and age influence intestinal parasite burden in three boreal grouse speciesJOURNAL OF AVIAN BIOLOGY, Issue 5 2006Marja Isomursu Parasite infections are often more common in male vertebrates than in females. Sexual selection leading to dimorphism can cause sexual differences in immune defence, behaviour or body size. Possible proximate explanations for male bias in parasitism are the immunosuppressive effect of male sex hormones and the large body size of males which increases the likelihood of being parasitized. To evaluate these hypotheses, we studied the prevalence and abundance of intestinal helminth parasites in three boreal grouse species, the capercaillie Tetrao urogallus, the black grouse Tetrao tetrix, and the hazel grouse Bonasa bonasia. The first two are sexually dimorphic polygynous species while the latter species is sexually monomorphic and monogamous. We found a male-bias in the prevalence and abundance of the nematode Ascaridia compar. The bias was most pronounced in the polygynous black grouse and capercaillie. In the monogamous hazel grouse, there was a slight male-bias in occurrence of ascarids, but no bias in abundance. In juvenile grouse, the male-bias was larger than in adult grouse. No sexual bias was found in regard to the cestodes (Skrjabinia cesticillus, Paroniella urogalli and Hymenolepis spp.). However, age was a factor in cestode prevalence: juvenile grouse were more commonly infected than adults. Differences in growth rates and body size are potential factors that may lead to male-biased parasitism in these grouse species, and their impact requires further studies. [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] On the hunt for helminths: innate immune cells in the recognition and response to helminth parasitesCELLULAR MICROBIOLOGY, Issue 9 2008Jacqueline G. Perrigoue Summary The generation of protective immunity to helminth parasites is critically dependent upon the development of a CD4+ T helper type 2 cytokine response. However, the host,parasite interactions responsible for initiating this response are poorly understood. This review will discuss recent advances in our understanding of how helminth-derived products are recognized by innate immune cells. Specifically, interactions between helminth excretory/secretory products and host Toll-like receptors and lectins will be discussed as well as the putative functions of helminth proteases and chitin in activating and recruiting innate immune cells. In addition, the functional significance of pattern recognition by epithelial cells, granulocytes, dendritic cells and macrophages including expression of alarmins, thymic stromal lymphopoetin, interleukin (IL)-25, IL-33 and Notch ligands in the development of adaptive anti-parasite Th2 cytokine responses will be examined. [source] Immune biasing by helminth glycansCELLULAR MICROBIOLOGY, Issue 1 2004Paul G. Thomas Summary The ability of helminth parasites to drive polarized Th2 responses has been known for some time. Interestingly, many recent studies have shown that helminth-expressed glycan activation of host immune cells accounts for much of the anti-inflammatory and Th2-biasing observed. This microreview attempts to cover the biology of expression of immunomodulatory glycans in various helminth parasites, the immune cells they interact with including the production of cytokines, chemokines and antibodies. We also discuss the potential,, cell,, surface,, receptors,, which,, are,, capable of binding certain glycans and the known mechanisms which ultimately lead to production of anti-inflammatory,, mediators,, as,, well,, as,, polarizing,, CD4+ T-cell responses to Th2-type in the host. Lastly, we discuss a novel mechanism for activation of antigen-presenting cells by a specific helminth glycan that leads to maturation of Type 2 dendritic cells. [source] Do helminth parasites protect against atopy and allergic disease?CLINICAL & EXPERIMENTAL ALLERGY, Issue 1 2009C. Flohr Summary Allergic diseases are rare in areas with high helminth parasite exposure and common where helminth exposure is lacking or significantly reduced, such as urban areas of developing countries and industrialized nations. Studies suggest that helminths induce a systemic immuno-modulatory network, including regulatory T cells and anti-inflammatory IL-10, which might play a key role in the protection against the allergic phenotype. Here, we review the current cross-sectional, birth cohort, and intervention study evidence for a protective effect of helminth infection on allergy. There is increasing evidence for a causal relationship between helminth infection and reduced skin prick test responsiveness to allergens. Cross-sectional studies have shown a consistent negative relationship, and these results have been confirmed in several, although not all, intervention studies. The immunological basis for this protective effect is less clear. Recent studies do not support the mast-cell IgE saturation hypothesis, but suggest that protection is associated with IL-10 production. As for allergic disease, cross-sectional studies support a negative relationship between clinical asthma and infection with some helminth species, particularly hookworm, but more studies are required to draw conclusions for eczema and rhinitis. In addition, none of the few intervention studies to date have demonstrated an increase in clinical allergy after helminth treatment, and further studies are needed. Furthermore, we are only beginning to understand the host genetic factors that are potentially involved. A genetically predetermined T-helper type 2 cell-dominated cytokine milieu reduces parasite burden and may enhance host survival in an environment where helminth parasites are prevalent. Lack of parasite exposure in such hosts might lead to hypersensitivity to seemingly minor environmental allergen stimuli. Large birth cohort studies in helminth-endemic areas that use epidemiological, genetic, and immunological tools are required to further examine how helminth parasites affect the development of atopy and allergic disease. Intervention studies with hookworm in parasite-naïve allergic individuals are currently ongoing in the United Kingdom to test the above hypotheses further. [source] | |||||||||||||