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There is considerable research interest in the role of helminth infections in the development of allergic diseases. However, findings from previous studies are mixed. Existing systematic reviews of these studies are outdated. We performed a systematic review of the global literature on the association between helminth infections and development and clinical outcomes of allergic diseases. We searched Cochrane Library, MEDLINE, EMBASE, ISI Web of Science, PubMed, Global Index Medicus, Scielo, KoreaMed, Google Scholar, and Lilacs for studies published up to January 2020. We included observational epidemiological studies (cohort, case-control, and cross-sectional studies) of children and adults reporting associations between helminth infections and asthma, allergic rhinitis, eczema, and atopy. We performed random-effects meta-analysis to summarize the effect estimates. We included 80 studies with 99,967 participants. In the meta-analyses, we did not observe an overall association between helminth infections and allergic diseases. There was, however, evidence that Ascaris lumbricoides infections were associated with an increased risk of bronchial hyperreactivity in children (risk ratio, 1.41; 95% CI, 1.17-1.70; I 2 = 50; P for I 2 =.09), and were associated with an increased risk of atopy among helminth-infected adults (risk ratio, 1.37; 95% CI, 1.18-1.61; I 2 = 52; P for I 2 =.02). We found no study that addressed the association between helminth infection and clinical outcomes of allergic diseases. The overall strength of the underlying evidence was low to moderate. Helminth infections may increase the risk of bronchial hyperreactivity in children and atopy in adults. Well-designed longitudinal cohorts may help clarify potential causal associations between chronic helminth infections and allergic diseases. [ABSTRACT FROM AUTHOR]

Background: Early‐life exposures to geohelminths may protect against development of wheeze/asthma and atopy. Objective: To study the effect of maternal geohelminths and infections in children during the first 5 years on atopy, wheeze/asthma and airways reactivity/inflammation at 8 years. Methods: Birth cohort of 2404 neonates followed to 8 years in rural Ecuador. Data on wheeze/asthma were collected by questionnaire and atopy by skin prick test (SPT) reactivity to 9 allergens. We measured airways reactivity to bronchodilator, fractional exhaled nitric oxide (FeNO) and nasal eosinophilia. Stool samples were examined for geohelminths by microscopy. Results: 1933 (80.4%) children were evaluated at 8 years. Geohelminths were detected in 45.8% of mothers and 45.5% of children to 5 years. Frequencies of outcomes at 8 years were as follows: wheeze (6.6%), asthma between 5 and 8 years (7.9%), SPT (14.7%), airways reactivity (10%) and elevated FeNO (10.3%) and nasal eosinophilia (9.2%). Any maternal geohelminth was associated with reduced SPT prevalence (OR 0.72). Childhood Trichuris trichiura infections during the first 5 years were associated with reduced wheeze (OR 0.57) but greater parasite burdens with Ascaris lumbricoides at 5 years were associated with increased wheeze (OR 2.83) and asthma (OR 2.60). Associations between maternal geohelminths and wheeze/asthma were modified by atopy. Parasite‐specific effects on wheeze/asthma and airways reactivity and inflammation were observed in non‐atopic children. Conclusions: Our data provide novel evidence for persistent effects of in utero geohelminth exposures on childhood atopy but highlight the complex nature of the relationship between geohelminths and the airways. Registered as an observational study (ISRCTN41239086). [ABSTRACT FROM AUTHOR]

Abstract In this work we explore differences in blood cells and cytokine profiles in children according to atopic status and asthma (atopic or non-atopic). The study involved measurement of Th1(IFN-γ) and Th2 (IL-5 and IL-13) cytokines in Dermatophagoides pteronyssinus stimulated peripheral blood leukocytes, blood cell count, skin prick test and specific IgE against common aeroallergens. Atopic status was associated with eosinophilia and production of Th2 type cytokines. Atopic asthma was associated with eosinophilia and non-atopic asthma was associated with IFN-γ and elevated monocytes in blood. IFN-γ and monocytes might play a role in immunopathology of non-atopic asthma in Latin American children.

Background: Rural residence is protective against atopy and wheeze-rhinitis-eczema symptoms in developed countries, an effect attributed to farming and poor hygiene exposures. There are few data from developing countries addressing this question. We compared atopy and wheeze-rhinitis-eczema symptoms between urban and rural Ecuador, and explored the effects of farming and poor hygiene exposures.Methods: We performed cross sectional studies of schoolchildren living in rural and urban Ecuador. Data on symptoms and farming/hygiene exposures were collected by parental questionnaire, atopy by allergen skin prick test reactivity and geohelminth infections by stool examinations.Results: Among 2526 urban and 4295 rural schoolchildren, prevalence was: atopy (10.0% vs 12.5%, p=0.06), wheeze (9.4% vs 10.1%, p=0.05), rhinitis (8.1% vs 6.4%, p=0.02) and eczema (5.9% vs 4.7%, p=0.06). A small proportion of symptoms were attributable to atopy (range 3.9-10.7%) with greater attributable fractions for respiratory symptoms observed in urban schoolchildren. Respiratory symptoms were associated with poor hygiene/farming exposures: wheeze with lack of access to potable water; and rhinitis with household pets, no bathroom facilities and contact with large farm animals. Birth order was inversely associated with respiratory symptoms. Area of residence and atopy had few effects on these associations.Conclusions: Urban schoolchildren living in Ecuador have a similar prevalence of atopy, eczema and wheeze but a higher prevalence of rhinitis compared with rural children. Some farming and poor hygiene exposures were associated with an increase in the prevalence of wheeze or rhinitis while birth order was inversely associated with these symptoms. [ABSTRACT FROM AUTHOR]

Background Asthma has emerged as an important public health problem of urban populations in Latin America. Epidemiological data suggest that a minority of asthma cases in Latin America may be associated with allergic sensitisation and that other mechanisms causing asthma have been overlooked. The aim of the present study was to investigate risk factors for atopic and non-atopic asthma in school-age children. Methods A cross-sectional study was conducted among 3960 children aged 6e16 years living in Afro-Ecuadorian rural communities in Esmeraldas province in Ecuador. Allergic diseases and risk factors were assessed by questionnaire and allergic sensitisation by allergen skin prick reactivity. Results A total of 390 (10.5%) children had wheeze within the previous 12 months, of whom 14.4% had at least one positive skin test. The population-attributable fraction for recent wheeze associated with atopy was 2.4%. Heavy Trichuris trichiura infections were strongly inversely associated with atopic wheeze. Non-atopic wheeze was positively associated with maternal allergic symptoms and sedentarism (watching television (>3 h/ day)) but inversely associated with age and birth order. Conclusions The present study showed a predominance of non-atopic compared with atopic wheeze among schoolchildren living in a poor rural region of tropical Latin America. Distinct risk factors were associated with the two wheeze phenotypes and may indicate different causal mechanisms. Future preventive strategies in such populations may need to be targeted at the causes of non-atopic wheeze. [ABSTRACT FROM AUTHOR]

Background. In areas where intestinal helminth infections are endemic, infections by these parasites may protect against skin test-measured reactivity to allergens, and it has been suggested that interleukin (IL)-10 may mediate this effect. This study investigated whether IL-10 and populations of IL-10+ T cells may modulate atopy in children living in an area where intestinal helminth infections are endemic. Methods. Ecuadorian schoolchildren from rural communities were assessed for skin test-measured reactivity to Periplaneta americana allergen and Dermatophagoides pteronyssinus allergen. Blood samples were collected from 39 skin test-positive and 41 skin test-negative children, and peripheral-blood leukocytes were cultured in the presence of Ascaris lumbricoides antigen, to measure IL-10 protein and the frequency of T cell populations expressing intracellular IL-10. We also investigated whether these immunological factors affected the association between allergen-specific IgE and skin test-measured reactivity to aeroallergens. Results. There was no evidence of association between the level of A. lumbricoides-induced IL-10 protein or IL-10+ T cells and skin test-measured reactivity to allergens. The association between allergen-specific IgE and skin test-measured reactivity was not affected by the level of IL-10 protein or the frequency of IL-10+ T cells. Conclusions. The results of this study do not support the notion that IL-10 plays a role in modulating atopy in children living in a tropical area where intestinal helminth infections are endemic. [ABSTRACT FROM AUTHOR]

Background Asthma is the most prevalent chronic disease of childhood. Recently, we identified a critical window early in the life of both mice and Canadian infants during which gut microbial changes (dysbiosis) affect asthma development. Given geographic differences in human gut microbiota worldwide, we studied the effects of gut microbial dysbiosis on atopic wheeze in a population living in a distinct developing world environment. Objective We sought to determine whether microbial alterations in early infancy are associated with the development of atopic wheeze in a nonindustrialized setting. Methods We conducted a case-control study nested within a birth cohort from rural Ecuador in which we identified 27 children with atopic wheeze and 70 healthy control subjects at 5 years of age. We analyzed bacterial and eukaryotic gut microbiota in stool samples collected at 3 months of age using 16S and 18S sequencing. Bacterial metagenomes were predicted from 16S rRNA data by using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States and categorized by function with Kyoto Encyclopedia of Genes and Genomes ontology. Concentrations of fecal short-chain fatty acids were determined by using gas chromatography. Results As previously observed in Canadian infants, microbial dysbiosis at 3 months of age was associated with later development of atopic wheeze. However, the dysbiosis in Ecuadorian babies involved different bacterial taxa, was more pronounced, and also involved several fungal taxa. Predicted metagenomic analysis emphasized significant dysbiosis-associated differences in genes involved in carbohydrate and taurine metabolism. Levels of the fecal short-chain fatty acids acetate and caproate were reduced and increased, respectively, in the 3-month stool samples of children who went on to have atopic wheeze. Conclusions Our findings support the importance of fungal and bacterial microbiota during the first 100 days of life on the development of atopic wheeze and provide additional support for considering modulation of the gut microbiome as a primary asthma prevention strategy. [ABSTRACT FROM AUTHOR]

Background: It has been proposed that improved hygiene and reduced experience of infections in childhood influences the development of allergic diseases. The mechanisms by which the hygiene operates are not well established but are underpinned by two apparently incompatible immunologic paradigms, the balance of TH1 versus TH2 cytokines and IL-10–mediated regulation of TH2 cytokines. Objective: This study defined immunologic phenotypes with the use of latent class analysis and investigated their associations with environmental factors, markers of allergy and asthma, in a Latin American population. Methods: We studied 1127 children living in urban Brazil. Data on wheeze and environmental exposures were collected with standardized questionnaires. Atopy was measured by specific IgE in serum and skin prick test reactivity to aeroallergens. Cytokines were measured in culture after the stimulation of peripheral blood leukocytes with mitogen. Infections with pathogens were assessed by serology and stool examinations. Children were classified as having high or low burden of infection. Latent class analysis was used to identify immune phenotypes on the basis of cytokine production. Logistic regression was used to evaluate the adjusted effects of environment and burden of infection on the immunologic phenotypes and the effect of the phenotypes on atopy and asthma. Results: Three phenotypes were identified, labeled underresponsive, intermediate, and responsive. Children of more educated mothers, living in improved environmental conditions, and with a low burden of infection were significantly more likely to have the responsive phenotype. The responsive phenotype was significantly associated with an increased prevalence of atopy but not asthma. Conclusion: Our findings contribute to a better understanding of the immune mechanisms by which the hygiene hypothesis operates in urban Latin America. [Copyright &y& Elsevier]

Toxocara canis , Toxocara cati , are roundworms that live in the intestines of dogs and cats, respectively, and are predominantly agents of human toxocariasis. Studies have suggested that Toxocara spp. seroprevalence increases levels of total and aeroallergen-specific IgE (sIgE), asthma prevalence and asthma morbidity. Nevertheless, other work reported a negative association between Toxocara spp. seropositivity with skin hypersensititity and a positive association with sIgE. The objective of the present study was to evaluate risk factors for acquiring Toxocara spp. infection and to investigate possible significant association between its seroprevalence with atopy and asthma. Students from elementary schools, residents in a small town and its surroundings of Northeast Brazil, underwent blood sampling to measure levels of anti- Toxocara spp. IgG, peripheral blood eosinophils, and specific IgE to aeroallergens. We used univariable and multivariable logistic regression analyses to assess possible risk factors for Toxocara spp. seropositivity and its association with atopy, wheeze/asthma with asthma phenotypes, in a sample of 791 elementary school children aged 6–13 years. Toxocara spp. seroprevalence reached 63.6%; 49.9% had sIgE; 7.2% and 3.3% had atopic wheeze/asthma and non-atopic wheeze/asthma respectively. Risk factors associated with Toxocara spp. seropositivity were: contact with dogs (adj. OR 2.33; 95% CI = 1.70–3.19) and cats (adj. OR 3.09; 95% CI = 2.10–4.55), and male sex (adj. OR 2.21; 95% CI = 1.62–3.02). The presence of anti- Toxocara IgG was statistically associated with blood eosinophils >4% and >10% (adj. OR 1.84; 95% CI = 1.33-2.55 and adj. OR 2.07; 95% CI = 1.45–2.97, respectively), and atopy (adj. OR 2.00; 95% CI = 1.49–2.68), but it was not associated with wheeze/asthma. Concluding, the results obtained in this study showing the association of Toxocara spp. seroprevalence with sIgE may suggest a possible immunological cross-reactivity between IgE epitopes from Toxocara spp. and aeroallergens. [ABSTRACT FROM AUTHOR]