Understanding and controlling asthma in Latin America: A review of recent research informed by the SCAALA programme

Asthma is an important health concern in Latin America (LA) where it is associated with variable prevalence and disease burden between countries. High prevalence and morbidity have been observed in some regions, particularly marginalized urban populations. Research over the past 10 years from LA has shown that childhood disease is primarily non-atopic. The attenuation of atopy may be explained by enhanced immune regulation induced by intense exposures to environmental factors such as childhood infections and poor environmental conditions of the urban poor. Non-atopic symptoms are associated with environmental and lifestyle factors including poor living conditions, respiratory infections, psychosocial stress, obesity, and a diet of highly processed foods. Ancestry (particularly African) and genetic factors increase asthma risk, and some of these factors may be specific to LA settings. Asthma in LA tends to be poorly controlled and depends on access to health care and medications. There is a need to improve management and access to medication through primary health care. Future research should consider the heterogeneity of asthma to identify relevant endotypes and underlying causes. The outcome of such research will need to focus on implementable strategies relevant to populations living in resource-poor settings where the disease burden is greatest.

Prospective study of factors associated with asthma attack recurrence (ATTACK) in children from three Ecuadorian cities during COVID-19: a study protocol

INTRODUCTION

Asthma is a growing health problem in children in marginalised urban settings in low-income and middle-income countries. Asthma attacks are an important cause of emergency care attendance and long-term morbidity. We designed a prospective study, the Asthma Attacks study, to identify factors associated with recurrence of asthma attacks (or exacerbations) among children and adolescents attending emergency care in three Ecuadorian cities.

METHODS AND ANALYSIS

Prospective cohort study designed to identify risk factors associated with recurrence of asthma attacks in 450 children and adolescents aged 5-17 years attending emergency care in public hospitals in three Ecuadorian cities (Quito, Cuenca and Portoviejo). The primary outcome will be rate of asthma attack recurrence during up to 12 months of follow-up. Data are being collected at baseline and during follow-up by questionnaire: sociodemographic data, asthma history and management (baseline only); recurrence of asthma symptoms and attacks (monthly); economic costs of asthma to family; Asthma Control Test; Pediatric Asthma Quality of life Questionnaire; and Newcastle Asthma Knowledge Questionnaire (baseline only). In addition, the following are being measured at baseline and during follow-up: lung function and reversibility by spirometry before and after salbutamol; fractional exhaled nitric oxide (FeNO); and presence of IgG antibodies to SARS-CoV-2 in blood. Recruitment started in 2019 but because of severe disruption to emergency services caused by the COVID-19 pandemic, eligibility criteria were modified to include asthmatic children with uncontrolled symptoms and registered with collaborating hospitals. Data will be analysed using logistic regression and survival analyses.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Hospital General Docente de Calderon (CEISH-HGDC 2019-001) and Ecuadorian Ministry of Public Health (MSP-CGDES-2021-0041-O N° 096-2021). The study results will be disseminated through presentations at conferences and to key stakeholder groups including policy-makers, postgraduate theses, peer-review publications and a study website. Participants gave informed consent to participate in the study before taking part.

The epidemiology of soil-transmitted helminth infections in children up to 8 years of age: Findings from an Ecuadorian birth cohort

Background

There are few prospective longitudinal studies of soil-transmitted helminth (STH) infections during early childhood. We studied the epidemiology of and risk factors for soil-transmitted helminth infections from birth to 8 years of age in tropical Ecuador.

Methods

2,404 newborns were followed to 8 years of age with periodic stool sample collections. Stool samples were collected also from household members at the time of the child’s birth and examined by microscopy. Data on social, environmental, and demographic characteristics were collected by maternal questionnaire. Associations between potential risk factors and STH infections were estimated using generalized estimated equations applied to longitudinal binary outcomes for presence or absence of infections at collection times.

Results

Of 2,404 children, 1,120 (46.6%) were infected with at least one STH infection during the first 8 years of life. The risk of A. lumbricoides (16.2%) was greatest at 3 years, while risks of any STH (25.1%) and T. trichiura (16.5%) peaked at 5 years. Factors significantly associated with any STH infection in multivariable analyses included age, day-care (OR 1.34, 95% CI 1.03–1.73), maternal Afro-Ecuadorian ethnicity (non-Afro vs. Afro, OR 0.55, 95% CI 0.43–0.70) and lower educational level (secondary vs. illiterate, OR 0.31, 95% CI 0.22–0.45)), household overcrowding (OR 1.53, 95% CI 1.21–1.94)), having a latrine rather than a water closet (WC vs. latrine, OR 0.77, 95% CI 0.62–0.95)), and STH infections among household members (OR 2.03, 95% CI 1.59–2.58)). T. trichiura was more associated with poverty (high vs. low socioeconomic status, OR, 0.63, 95% CI 0.40–0.99)] and presence of infected siblings in the household (OR 3.42, 95% CI 2.24–5.22).

Conclusion

STH infections, principally with A. lumbricoides and T. trichiura, peaked between 3 and 5 years in this cohort of children in tropical Ecuador. STH infections among household members were an important determinant of infection risk and could be targeted for control and elimination strategies.

Soil-transmitted helminths (STH) cause significant morbidity among children in low and middle-income countries (LMICs). We followed a birth cohort to 8 years of age in a rural area of coastal Ecuador and showed almost half acquired STH infections during childhood. The dominant STH parasites in this setting in children were Ascaris lumbricoides and Trichuris trichiura and infections peaked in frequency between 3 and 5 years of age. Risk of infection during childhood was associated with markers of marginalisation (Afro-Ecuadorian ethnicity and low educational level), household poverty (overcrowding and poor sanitation), and STH infections among other household members. There was evidence of a reduction in STH infection risk across all ages in study households over the calendar time course of this longitudinal study in parallel with improvements in living conditions, a period of economic growth, and increased government support for those living in extreme poverty. Our data indicate that targeting anthelmintic treatment at members of STH-infected households is likely to reduce the risk of infection in young children.

Impact of early life geohelminths on wheeze, asthma and atopy in Ecuadorian children at 8 years

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).

Incidence and seasonality of respiratory viruses among medically attended children with acute respiratory infections in an Ecuador birth cohort, 2011-2014

Background

Ecuador annually has handwashing and respiratory hygiene campaigns and seasonal influenza vaccination to prevent respiratory virus illnesses but has yet to quantify disease burden and determine epidemic timing.

Methods

To identify respiratory virus burden and assess months with epidemic activity, we followed a birth cohort in northwest Ecuador during 2011–2014. Mothers brought children to the study clinic for routine checkups at ages 1, 2, 3, 5, and 8 years or if children experienced any acute respiratory illness symptoms (e.g., cough, fever, or difficulty breathing); clinical care was provided free of charge. Those with medically attended acute respiratory infections (MAARIs) were tested for common respiratory viruses via real‐time reverse‐transcription polymerase chain reaction (rRT‐PCR).

Results

In 2011, 2376 children aged 1–4 years (median 35 months) were enrolled in the respiratory cohort and monitored for 7017.5 child‐years (cy). The incidence of respiratory syncytial virus (RSV) was 23.9 (95% CI 17.3–30.5), influenza 10.6 (2.4–18.8), adenoviruses 6.7 (4.6–28.0), parainfluenzas 5.0 (2.3–10.5), and rhinoviruses, bocaviruses, human metapneumoviruses, seasonal coronaviruses, and enteroviruses <3/100 cy among children aged 12–23 months and declined with age. Most (75%) influenza detections occurred April–September.

Conclusion

Cohort children frequently had MAARIs, and while the incidence decreased rapidly among older children, more than one in five children aged 12–23 months tested positive for RSV, and one in 10 tested positive for influenza. Our findings suggest this substantial burden of influenza occurred more commonly during the winter Southern Hemisphere influenza season.

Patterns of allergic sensitization and factors associated with emergence of sensitization in the rural tropics early in the life course: findings of an Ecuadorian birth cohort

Introduction

There are limited data on emergence of allergic sensitization (or atopy) during childhood in tropical regions.

Methods

We followed a birth cohort of 2404 newborns to 8 years in tropical Ecuador and collected: risk factor data by maternal questionnaires periodically from birth; atopy was measured by skin prick test reactivity (SPT) to aeroallergens in parents, and aeroallergens and food allergens in children at 2, 3, 5, and 8 years; and stool samples for soil-transmitted helminths (STH) from children periodically to 8 years and from parents and household members at the time of recruitment of cohort children. Data on risk factors were measured either at birth or repeatedly (time-varying) from birth to 8 years. Longitudinal repeated-measures analyses were done using generalized estimating equations to estimate an the age-dependent risk of positive SPT (SPT+) to any allergen or mite during early childhood to school age.

Results

SPT+ to any allergen was present in 29.0% of fathers and 24.8% of mothers, and in cohort children increased with age, initially to mite but later to cockroach, reaching 14.8% to any allergen (10.7% mite and 5.3% cockroach) at 8 years. Maternal SPT+, particularly presence of polysensitization (OR 2.04, 95% CI 1.49-2.77) significantly increased the risk of SPT+ during childhood, while household overcrowding at birth decreased the risk (OR 0.84, 95% CI 0.72-0.98). For mite sensitization, maternal polysensitization increased (OR 2.14, 95% CI 1.40-3.27) but rural residence (OR 0.69, 95% CI 0.50-0.94) and birth order (3^rd -4^th vs. 1^st - 2^nd: OR 0.71, 95% CI 0.52-0.98) decreased the risk. Time-varying exposures to agricultural activities (OR 0.77, 95% CI 0.60-0.98) and STH parasites (OR 0.70, 95% CI 0.64-0.91) during childhood decreased while anthelmintics increased the childhood risk (OR 1.47, 95% CI 1.05-2.05) of mite sensitization.

Conclusion

Our data showed the emergence of allergic sensitization, primarily to mite and cockroach allergens, during childhood in tropical Ecuador. A role for both antenatal and postnatal factors acting as potential determinants of SPT+ emergence was observed.

Effect of Early-Life Geohelminth Infections on the Development of Wheezing at 5 Years of Age

RATIONALE

Exposures to geohelminths during gestation or early childhood may reduce risk of wheezing illness/asthma and atopy during childhood in tropical regions.

OBJECTIVES

To investigate the effect of maternal and early childhood geohelminths on development of wheeze/asthma and atopy during the first 5 years of life.

METHODS

A cohort of 2,404 neonates was followed to 5 years of age in a rural district in coastal Ecuador. Data on wheeze were collected by questionnaire and atopy was measured by allergen skin prick test reactivity to 10 allergens at 5 years. Stool samples from mothers and children were examined for geohelminths by microscopy.

MEASUREMENTS AND MAIN RESULTS

A total of 2,090 (86.9%) children were evaluated at 5 years. Geohelminths were observed in 45.5% of mothers and in 34.1% of children by 3 years. Wheeze and asthma were reported for 12.6% and 5.7% of children, respectively, whereas 14.0% had skin test reactivity at 5 years. Maternal geohelminths were associated with an increased risk of wheeze (adjusted odds ratio, 1.41; 95% confidence interval, 1.06-1.88), whereas childhood geohelminths over the first 3 years of life were associated with reduced risk of wheeze (adjusted odds ratio, 0.70; 95% confidence interval, 0.52-0.96) and asthma (adjusted odds ratio, 0.60; 95% confidence interval, 0.38-0.94) but not skin prick test reactivity. The effects on wheeze/asthma were greatest with later age of first infection, were observed only in skin test-negative children, but were not associated with parasite burden or specific geohelminths.

CONCLUSIONS

Although maternal exposures to geohelminths may increase childhood wheeze, childhood geohelminths during the first 3 years may provide protection through a nonallergic mechanism. Registered as an observational study (ISRCTN41239086).

Soil-transmitted helminth parasites and allergy: Observations from Ecuador

There is considerable interest as to potential protective effects of soil-transmitted helminths (STH) against allergy and allergic diseases. Here, we discuss findings of studies done of the effects of STH parasites on atopy and allergic diseases in Ecuador. While cross-sectional studies have consistently shown a reduced prevalence of allergen skin prick test (SPT) reactivity among infected schoolchildren, the removal of these infections by repeated deworming did not affect SPT prevalence over the short-term (ie, 12 months) but may have increased SPT prevalence over the long-term (ie, 15-17 years). In the case of allergic symptoms, cross-sectional studies have generally not shown associations with STH and intervention studies showed no impact on prevalence. However, a birth cohort suggested that early STH infections might reduce wheeze by 5 years. Allergic sensitization to Ascaris, however, explained a significant proportion of wheezing among rural schoolchildren. Studies of the effects of STH on immune and inflammatory responses indicated a potential role of STH in contributing to more robust regulation. The effects of STH on allergy are likely to be determined by history of exposure over the life-course and by interactions with a wide variety of other infectious and non-infectious factors.

Associations between infant fungal and bacterial dysbiosis and childhood atopic wheeze in a nonindustrialized setting

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.

Growth patterns in early childhood: Better trajectories in Afro-Ecuadorians independent of sex and socioeconomic factors

The first years of life are the most dynamic period for childhood growth. There are limited data available on growth patterns of infants and children living in rural Latin America. The aim of this study was to describe the growth patterns from birth to 5years in children living in a rural District of tropical coastal Ecuador using data from a birth cohort of 2404 neonates. We hypothesize that there would be growth differences according to ethnicity and sex. Evaluations were conducted at birth or until 2weeks of age and at 7, 13, 24, 36 and 60months during clinic and home visits. Individual growth trajectories for weight-for-age, height-for-age and weight/height-for-age Z-scores were estimated using multilevel models. Girls were lighter and shorter than boys at birth. However, Afro-Ecuadorian children (versus mestizo or indigenous) were longer/taller and heavier throughout the first 5years of life and had greater mean trajectories for HAZ and WAZ independent of sex and socioeconomic factors. Our data indicate that ethnicity is a determinant of growth trajectories during the first 5years of life independent of socioeconomic factors in a birth cohort conducted in a rural region of Latin America.

Rural to urban migration is associated with increased prevalence of childhood wheeze in a Latin-American city

Introduction

The urbanisation process has been associated with increases in asthma prevalence in urban and rural areas of low-income and middle-income countries (LMICs). However, although rural to urban migration and migration between cities are considered important determinants of this process, few studies have evaluated the effects of internal migration on asthma in urban populations of LMICs. The present study evaluated the effects of internal migration on the prevalence of wheeze in an urban area of Latin America.

Methods

We did a cross-sectional analysis of 2510 schoolchildren living in the city of Esmeraldas, Ecuador. Logistic regression was used to analyse associations between childhood wheeze and different aspects of migration among schoolchildren.

Results

31% of schoolchildren were migrants. Rural to urban migrants had a higher prevalence of wheeze, (adj.OR=2.01,95% CI1.30 to 3.01, p=0.001) compared with non-migrants. Age of migration and time since migration were associated with wheeze only for rural to urban migrants but not for urban to urban migrants. Children who had migrated after 3 years of age had a greater risk of wheeze (OR 2.51, 95% CI 1.56 to 3.97, p=0.001) than non-migrants while migrants with less than 5 years living in the new residence had a higher prevalence of wheeze than non-migrants (<3 years: OR=2.34, 95% CI 1.26 to 4.33, p<0.007 and 3–5 years: OR=3.03, 95% CI 1.49 to 6.15, p<0.002).

Conclusions

Our study provides evidence that rural to urban migration is associated with an increase in the prevalence of wheeze among schoolchildren living in a Latin-American city. Age of migration and time since migration were important determinants of wheeze only among migrants from rural areas. A better understanding of the social and environmental effects of internal migration could improve our understanding of the causes of the increase in asthma and differences in prevalence between urban and rural populations.

Effects of poor hygiene on cytokine phenotypes in children in the tropics

We describe immune phenotypes (innate and adaptive cytokines) according to environmental exposure using latent class analysis. A total of 310 schoolchildren living in Ecuador were assayed for spontaneous cytokine production as well as mitogen (SEB)-stimulated cytokines in whole blood cultures. We collected data on environmental exposures by questionnaire and on intestinal parasites by examination of stool samples. Latent class analysis (LCA) was used to group children according to their innate (IL-6, IL-8, IL-10 and TNF-α) and adaptive (IL-5, IL-13, IL-17, IFN-γ and IL-10) cytokine profile. We also conducted multiple-group LCA and LCA with covariates to evaluate the effect of predictors on profile membership. We identified both hyporesponsive and Th2-modified immune phenotypes produced by peripheral blood leukocytes (PBLs) that were associated with intestinal worms and birth order, providing insights into how poor hygiene mediates immunologic effects on immune-mediated diseases.

Maternal Helminth Infection Is Associated With Higher Infant Immunoglobulin A Titers to Antigen in Orally Administered Vaccines

BACKGROUND

Many studies have documented lower vaccine efficacy among children in low-income countries, compared with their counterparts in high-income countries. This disparity is especially apparent with respect to oral vaccines such as rotavirus and oral polio vaccines. One potential contributing factor is the presence of maternal antenatal helminth infections, which can modulate the infant's developing immune system.

METHODS

Using a multiplex immunoassay, we tested plasma immunoglobulin A (IgA) or immunoglobulin G (IgG) levels specific for antigens in 9 routinely administered childhood vaccines among 1639 children aged approximately 13 months enrolled in the ECUAVIDA (Ecuador Life) birth cohort study in Ecuador. We compared vaccine responses in 712 children of mothers who tested positive for helminth infections in the last trimester of pregnancy to responses in 927 children of mothers without helminth infection.

RESULTS

Plasma IgA levels specific for antigens in rotavirus vaccine and oral polio vaccine containing poliovirus serotypes 1 and 3 were all significantly higher in children of helminth-infected mothers, compared with children of uninfected mothers. Plasma IgG levels specific for diphtheria, tetanus, pertussis, measles, rubella, and Haemophilus influenzae type b vaccine antigens were comparable between the 2 groups.

CONCLUSIONS

Antenatal maternal helminth infections were not associated with reduced antibody responses to infant vaccines, but rather with modestly increased IgA responses to oral vaccines.

Effects of maternal geohelminth infections on allergy in early childhood

Background

Maternal geohelminth infections during pregnancy may protect against allergy development in childhood.

Objective

We sought to investigate the effect of maternal geohelminths on the development of eczema, wheeze, and atopy during the first 3 years of life.

Methods

A cohort of 2404 neonates was followed to 3 years of age in a rural district in coastal Ecuador. Data on wheeze and eczema were collected by means of questionnaire and physical examination at 13, 24, and 36 months of age. Atopy was measured based on skin prick test (SPT) reactivity to 9 allergens at 36 months. Maternal stool samples were examined for geohelminths by microscopy. Data on potential confounders was collected after birth by questionnaire.

Results

Geohelminths were observed in 45.9% of mothers. Eczema and wheeze were reported for 17.7% and 25.9%, respectively, of 2069 (86.1%) children with complete follow-up to 3 years, and allergen SPT reactivity to any allergen was present in 17.2% and to house dust mite in 8.7%. Maternal geohelminth infections were not significantly associated with eczema (adjusted odds ratio [OR], 1.26; 95% CI, 0.98-1.61), wheeze (adjusted OR, 1.02; 95% CI, 0.82-1.27), and SPT reactivity to any allergen (adjusted OR, 0.79; 95% CI, 0.61-1.01). In subgroup analyses maternal geohelminths were associated with a significantly reduced risk of SPT reactivity to mite and other perennial allergens, and maternal ascariasis was associated with an increased risk of eczema and reduced risk of SPT reactivity to all allergens.

Conclusion

Our data do not support a protective effect of maternal infections with geohelminth parasites during pregnancy against the development of eczema and wheeze in early childhood, although there was evidence in subgroup analyses for a reduction in SPT reactivity to house dust mites and perennial allergens.

Effect of urban vs. rural residence on the association between atopy and wheeze in Latin America: findings from a case-control analysis

Background

The association between atopy and asthma is attenuated in non-affluent populations, an effect that may be explained by childhood infections such as geohelminths.

Objective

To investigate the association between atopy and wheeze in schoolchildren living in urban and rural areas of Ecuador and examine the effects of geohelminths on this association.

Methods

We performed nested case–control studies among comparable populations of schoolchildren living in rural communities and urban neighbourhoods in the Province of Esmeraldas, Ecuador. We detected geohelminths in stool samples, measured recent wheeze and environmental exposures by parental questionnaire, and atopy by specific IgE (sIgE) and skin prick test (SPT) reactivity to aeroallergens.

Results

Atopy, particularly sIgE to house dust mite (HDM), was more strongly associated with recent wheeze in urban than rural schoolchildren: (urban, adj. OR 5.19, 95% CI 3.37–8.00, P < 0.0001; rural, adj. OR 1.81, 95%CI 1.09–2.99, P = 0.02; interaction, P < 0.001). The population fractions of wheeze attributable to atopy were approximately two-fold greater in urban schoolchildren: SPT to any allergen (urban 23.5% vs. rural 10.1%), SPT to HDM (urban 18.5% vs. rural 9.6%), and anti-HDM IgE (urban 26.5% vs. rural 10.5%), while anti-Ascaris IgE was related to wheeze in a high proportion of rural (49.7%) and urban (35.4%) children. The association between atopy and recent wheeze was attenuated by markers of geohelminth infections.

Conclusions

Our data suggest that urban residence modifies the association between HDM atopy and recent wheeze, and this effect is explained partly by geohelminth infections.

Effects of environment on human cytokine responses during childhood in the tropics: role of urban versus rural residence

BACKGROUND

Environment may have a key role in the development of the immune system in childhood and environmental exposures associated with rural residence may explain the low prevalence of allergic and autoimmune diseases in the rural tropics. We investigated the effects of urban versus rural residence on the adaptive immune response in children living in urban and rural areas in a tropical region of Latin America.

METHODS

We recruited school children in either rural communities in the Province of Esmeraldas or in urban neighborhoods in the city of Esmeraldas, Ecuador. We collected data on environmental exposures by questionnaire and on intestinal parasites by examination of stool samples. Peripheral blood leukocytes (PBLs) in whole blood were stimulated with superantigen, parasite antigens and aeroallergens and IFN-γ, IL-5, IL-10, IL-13, and IL-17 were measured in supernatants.

RESULTS

We evaluated 440 school children; 210 living in rural communities and 230 in the city of Esmeraldas. Overall, urban children had greater access to piped water (urban 98.7 % vs. rural 1.9 %), were more likely to have a household bathroom (urban 97.4 % vs. rural 54.8 %), and were less likely to be infected with soil-transmitted helminth infections (urban 20.9 % vs. rural 73.5 %). Generally, detectable levels of cytokines were more frequent in blood from children living in urban than rural areas. Urban residence was associated with a significantly greater frequency of IL-10 production spontaneously (adjusted OR 2.56, 95 % CI 1.05-6.24) and on stimulation with Ascaris (adj. OR 2.5, 95 % CI 1.09-5.79) and house dust mite (adj. 2.24, 95 % CI 1.07-4.70) antigens. Analysis of effects of environmental exposures on SEB-induced IL-10 production within urban and rural populations showed that some environmental exposures indicative of poor hygiene (urban - higher birth order, A. lumbricoides infection; rural - no bathroom, more peri-domiciliary animals, and living in a wood/bamboo house) were associated with elevated IL-10.

CONCLUSIONS

In our study population, the immune response of children living in an urban environment was associated more frequently with the production of the immune regulatory cytokine, IL-10. Some factors related to poor hygiene and living conditions were associated with elevated IL-10 production within urban and rural populations.

Norovirus Infection and Disease in an Ecuadorian Birth Cohort: Association of Certain Norovirus Genotypes With Host FUT2 Secretor Status

BACKGROUND

Although norovirus is the most common cause of gastroenteritis, there are few data on the community incidence of infection/disease or the patterns of acquired immunity or innate resistance to norovirus.

METHODS

We followed a community-based birth cohort of 194 children in Ecuador with the aim to estimate (1) the incidence of norovirus gastroenteritis from birth to age 3 years, (2) the protective effect of norovirus infection against subsequent infection/disease, and (3) the association of infection and disease with FUT2 secretor status.

RESULTS

Over the 3-year period, we detected a mean of 2.26 diarrheal episodes per child (range, 0-12 episodes). Norovirus was detected in 260 samples (18%) but was not found more frequently in diarrheal samples (79 of 438 [18%]), compared with diarrhea-free samples (181 of 1016 [18%]; P = .919). A total of 66% of children had at least 1 norovirus infection during the first 3 years of life, and 40% of children had 2 infections. Previous norovirus infections were not associated with the risk of subsequent infection. All genogroup II, genotype 4 (GII.4) infections were among secretor-positive children (P < .001), but higher rates of non-GII.4 infections were found in secretor-negative children (relative risk, 0.56; P = .029).

CONCLUSIONS

GII.4 infections were uniquely detected in secretor-positive children, while non-GII.4 infections were more often found in secretor-negative children.

A genetic analysis of Trichuris trichiura and Trichuris suis from Ecuador

Background

Since the nematodes Trichuris trichiura and T. suis are morphologically indistinguishable, genetic analysis is required to assess epidemiological cross-over between people and pigs. This study aimed to clarify the transmission biology of trichuriasis in Ecuador.

Findings

Adult Trichuris worms were collected during a parasitological survey of 132 people and 46 pigs in Esmeraldas Province, Ecuador. Morphometric analysis of 49 pig worms and 64 human worms revealed significant variation. In discriminant analysis morphometric characteristics correctly classified male worms according to host species. In PCR-RFLP analysis of the ribosomal Internal Transcribed Spacer (ITS-2) and 18S DNA (59 pig worms and 82 human worms), nearly all Trichuris exhibited expected restriction patterns. However, two pig-derived worms showed a “heterozygous-type” ITS-2 pattern, with one also having a “heterozygous-type” 18S pattern. Phylogenetic analysis of the mitochondrial large ribosomal subunit partitioned worms by host species. Notably, some Ecuadorian T. suis clustered with porcine Trichuris from USA and Denmark and some with Chinese T. suis.

Conclusion

This is the first study in Latin America to genetically analyse Trichuris parasites. Although T. trichiura does not appear to be zoonotic in Ecuador, there is evidence of genetic exchange between T. trichiura and T. suis warranting more detailed genetic sampling.

Lifestyle domains as determinants of wheeze prevalence in urban and rural schoolchildren in Ecuador: cross sectional analysis

BACKGROUND

The acquisition of a modern lifestyle may explain variations in asthma prevalence between urban and rural areas in developing countries. However, the effects of lifestyle on asthma have been investigated as individual factors with little consideration given to the effects of lifestyle as a set of attributes. The aim of the present study was to identify modern lifestyle domains and assess how these domains might explain wheeze prevalence in urban and rural areas.

METHODS

We analysed data from cross-sectional studies of urban and rural schoolchildren in Esmeraldas Province, Ecuador. Variables were grouped as indicators of socioeconomic factors, sedentarism, agricultural activities and household characteristics to represent the main lifestyle features of the study population. We used multiple correspondence analyses to identify common lifestyle domains and cluster analysis to allocate children to each domain. We evaluated associations between domains and recent wheeze by logistic regression.

RESULTS

We identified 2-3 lifestyle domains for each variable group. Although wheeze prevalence was similar in urban (9.4%) and rural (10.3%) schoolchildren, lifestyle domains presented clear associations with wheeze prevalence. Domains relating to home infrastructure (termed transitional, rudimentary, and basic urban) had the strongest overall effect on wheeze prevalence in both urban (rudimentary vs. basic urban, OR = 2.38, 95% CI 1.12-5.05, p = 0.024) and rural areas (transitional vs. basic urban, OR = 2.02, 95% CI 1.1-3.73, p = 0.024; rudimentary vs. basic urban, OR = 1.88, 95% CI 1.02-3.47, p = 0.043). A high level of sedentarism was associated with wheeze in the rural areas only (OR = 1.64, 95% CI 1.23-2.18, p = 0.001).

CONCLUSIONS

We identified lifestyle domains associated with wheeze prevalence, particularly living in substandard housing and a high level of sedentarism. Such factors could be modified through programmes of improved housing and education. The use of lifestyle domains provides an alternative methodology for the evaluation of variations in wheeze prevalence in populations with different levels of development.

Cohort Profile: The Ecuador Life (ECUAVIDA) study in Esmeraldas Province, Ecuador

The ECUAVIDA birth cohort is studying the impact of exposures to soil-transmitted helminth (STH) parasites and early-life microbial exposures on the development of atopy, allergic diseases and immune responses in childhood. A total of 2404 newborns were recruited between 2006 and 2009 in a public hospital serving the rural district of Quininde, Esmeraldas Province, in a tropical region of coastal Ecuador. Detailed measurements were done around the time of the birth, at 7 and 13 months and at 2 and 3 years, and data collection is ongoing at 5 and 8 years. Data being collected include questionnaires for: sociodemographic, lifestyle, psychosocial (at 4-6 years only) and dietary (at 6-7 years only) factors; childhood morbidity and clinical outcomes; stool samples for parasites; blood samples for DNA, measurements of vaccine responses and other measures of immune function/inflammation; and anthropometrics. Allergen skin prick test reactivity is done from 2 years and measures of airway function and inflammation at 8 years.

Hygiene, atopy and wheeze-eczema-rhinitis symptoms in schoolchildren from urban and rural Ecuador

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.

Effects of geohelminth infection and age on the associations between allergen-specific IgE, skin test reactivity and wheeze: a case-control study

Background

Most childhood asthma in poor populations in Latin America is not associated with aeroallergen sensitization, an observation that could be explained by the attenuation of atopy by chronic helminth infections or effects of age.

Objective

To explore the effects of geohelminth infections and age on atopy, wheeze, and the association between atopy and wheeze.

Methods

A case-control study was done in 376 subjects (149 cases and 227 controls) aged 7–19 years living in rural communities in Ecuador. Wheeze cases, identified from a large cross-sectional survey, had recent wheeze and controls were a random sample of those without wheeze. Atopy was measured by the presence of allergen-specific IgE (asIgE) and skin prick test (SPT) responses to house dust mite and cockroach. Geohelminth infections were measured in stools and anti-Ascaris IgE in plasma.

Results

The fraction of recent wheeze attributable to anti-Ascaris IgE was 45.9%, while those for SPT and asIgE were 10.0% and 10.5% respectively. The association between atopy and wheeze was greater in adolescents than children. Although Anti-Ascaris IgE was strongly associated with wheeze (adj. OR 2.24 (95% CI 1.33–3.78, P = 0.003) and with asIgE (adj. OR 5.34, 95% CI 2.49–11.45, P < 0.001), the association with wheeze was independent of asIgE. There was some evidence that the association between atopy and wheeze was greater in uninfected subjects compared with those with active geohelminth infections.

Conclusions and clinical relevance

Atopy to house dust mite and cockroach explained few wheeze cases in our study population, while the presence of anti-Ascaris IgE was an important risk factor. Our data provided only limited evidence that active geohelminth infections attenuated the association between atopy and wheeze in endemic areas or that age modified this association. The role of allergic sensitization to Ascaris in the development of wheeze, independent of atopy, requires further investigation.

Urbanisation is associated with prevalence of childhood asthma in diverse, small rural communities in Ecuador

Background

Studies conducted in transitional communities from Africa and Asia have pointed to the process of urbanisation as being responsible for the increase in asthma prevalence in developing regions. In Latin America, there are few published data available on the potential impact of urbanisation on asthma prevalence. The aim of the present study was to explore how the process of urbanisation may explain differences in asthma prevalence in transitional communities in north-eastern Ecuador.

Methodology/principal findings

An ecological study was conducted in 59 communities in Esmeraldas Province, Ecuador. Indicators of urbanisation were grouped into three indices representing the processes associated with urbanisation: socioeconomic, lifestyle and urban infrastructure. Categorical principal components analysis was used to generate scores for each index and a fourth index—a summary urbanisation index—was derived from the most representative variables in each of the three indices. The authors analysed the associations between community asthma prevalence and the indices, as well as with each indicator variable of every group. The overall prevalence of asthma was 10.1% (range 0–31.4% between communities). Three of the four indices presented significant associations with community asthma prevalence: socioeconomic (r=0.295, p=0.023), lifestyle (r=0.342, p=0.008) and summary urbanisation index (r=0.355, p=0.006). Variables reflecting better socioeconomic status and a more urban lifestyle were associated with greater asthma prevalence.

Conclusions

These data provide evidence that the prevalence of asthma increases with increasing levels of urbanisation in transitional communities, and factors associated with greater socioeconomic level and changes towards a more urban lifestyle may be particularly important.

Impact of early life exposures to geohelminth infections on the development of vaccine immunity, allergic sensitization, and allergic inflammatory diseases in children living in tropical Ecuador: the ECUAVIDA birth cohort study

Background

Geohelminth infections are highly prevalent infectious diseases of childhood in many regions of the Tropics, and are associated with significant morbidity especially among pre-school and school-age children. There is growing concern that geohelminth infections, particularly exposures occurring during early life in utero through maternal infections or during infancy, may affect vaccine immunogenicity in populations among whom these infections are endemic. Further, the low prevalence of allergic disease in the rural Tropics has been attributed to the immune modulatory effects of these infections and there is concern that widespread use of anthelmintic treatment in high-risk groups may be associated with an increase in the prevalence of allergic diseases. Because the most widely used vaccines are administered during the first year of life and the antecedents of allergic disease are considered to occur in early childhood, the present study has been designed to investigate the impact of early exposures to geohelminths on the development of protective immunity to vaccines, allergic sensitization, and allergic disease.

Methods/Design

A cohort of 2,403 neonates followed up to 8 years of age. Primary exposures are infections with geohelminth parasites during the last trimester of pregnancy and the first 2 years of life. Primary study outcomes are the development of protective immunity to common childhood vaccines (i.e. rotavirus, Haemophilus influenzae type B, Hepatitis B, tetanus toxoid, and oral poliovirus type 3) during the first 5 years of life, the development of eczema by 3 years of age, the development of allergen skin test reactivity at 5 years of age, and the development of asthma at 5 and 8 years of age. Potential immunological mechanisms by which geohelminth infections may affect the study outcomes will be investigated also.

Discussion

The study will provide information on the potential effects of early exposures to geohelminths (during pregnancy and the first 2 years of life) on the development of vaccine immunity and allergy. The data will inform an ongoing debate of potential effects of geohelminths on child health and will contribute to policy decisions on new interventions designed to improve vaccine immunogenicity and protect against the development of allergic diseases.

Trial registration

Current Controlled Trials ISRCTN41239086.

Immune system development during early childhood in tropical Latin America: evidence for the age-dependent down regulation of the innate immune response

The immune response that develops in early childhood underlies the development of inflammatory diseases such as asthma and there are few data from tropical Latin America (LA). This study investigated the effects of age on the development of immunity during the first 5 years of life by comparing innate and adaptive immune responses in Ecuadorian children aged 6–9 months, 22–26 months, and 48–60 months. Percentages of naïve CD4+ T cells declined with age while those of memory CD4⁺ and CD8⁺ T cells increased indicating active development of the immune system throughout the first five years. Young infants had greater innate immune responses to TLR agonists compared to older children while regulatory responses including SEB-induced IL-10 and percentages of FoxP3⁺ T-regulatory cells decreased with age. Enhanced innate immunity in early life may be important for host defense against pathogens but may increase the risk of immunopathology.

Risk factors for atopic and non-atopic asthma in a rural area of Ecuador

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 6–16 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.

Long-term periodic anthelmintic treatments are associated with increased allergen skin reactivity

Background

The low prevalence of allergic disease in the rural tropics has been attributed to the protective effects of chronic helminth infections. There is concern that treatment-based control programmes for these parasites may lead to an increase in the prevalence of allergic diseases.

Objective

We measured the impact of 15–17 years of anthelmintic treatment with ivermectin on the prevalence of allergen skin test reactivity and allergic symptoms in school-age children.

Methods

The prevalence of allergen skin test reactivity, exercise-induced bronchospasm and allergic symptoms was compared between school-age children living in communities that had received community-based treatments with ivermectin (for onchocerciasis control) for a period of 15–17 years with those living in geographically adjacent communities that had received no ivermectin.

Results

The prevalence of allergen skin test reactivity was double in children living in treated communities compared with those in untreated communities (16.7% vs. 8.7%, adjusted OR 2.10, 95% CI 1.50–2.94, P<0.0001), and the effect was mediated partly by a reduced prevalence of Trichuris trichiura among treated children. Ivermectin treatments were associated with an increased prevalence of recent eczema symptoms (adjusted OR 2.24, 95% CI 1.05–4.78, P=0.04) but not symptoms of asthma or rhino-conjunctivitis. The effect on eczema symptoms was not associated with reductions in geohelminth infections.

Conclusion

Long-term periodic treatments with ivermectin were associated with an increased prevalence of allergen skin test reactivity. There was some evidence that treatment was associated with an increased prevalence of recent eczema symptoms but not those of asthma or rhino-conjunctivitis.

Cite this as: P. Endara, M. Vaca, M. E. Chico, S. Erazo, G. Oviedo, I. Quinzo, A. Rodriguez R. Lovato, A.-L. Moncayo, M. L. Barreto, L. C. Rodrigues and P. J. Cooper, Clinical & Experimental Allergy, 2010 (40) 1669–1677.

High prevalence of bacterial vaginosis in adolescent girls in a tropical area of Ecuador

Bacterial vaginosis (BV) is a common clinical syndrome, but data are scarce on the BV prevalence in tropical regions among sexually active and virgin adolescents. To estimate the prevalence of BV among adolescent girls in an Ecuadorian coastal town, girls were asked to complete a questionnaire on risk factors for BV and vaginal samples were examined. Bacterial vaginosis was present in 31.5% of 213 girls, and the prevalence was similar in self-reported virgin and sexually active girls (OR 1.06, 95% CI, 0.51-2.21, P = 0.88), although the power of this analysis was limited. The prevalence of BV was high among Ecuadorian adolescent girls, and did not appear to be associated with sexual activity.

Evidence for in utero sensitization to Ascaris lumbricoides in newborns of mothers with ascariasis

Ascaris lumbricoides infections in humans may have important effects on the development of allergy and on susceptibility to infectious diseases that start during early life. To investigate whether sensitization to A. lumbricoides occurs in utero, we measured interferon (IFN)-gamma and interleukin (IL)-4 responses in A. lumbricoides antigen-stimulated cord blood from newborns of infected and noninfected mothers by flow cytometry. There was evidence of higher frequencies of IFN-gamma-expressing and IL-4-expressing CD4+ T cells in newborns of infected mothers than in newborns of noninfected mothers. Our data provide evidence of in utero sensitization to A. lumbricoides and raise the possibility that the immunological effects of infection start in the fetus.

Ascaris lumbricoides-induced interleukin-10 is not associated with atopy in schoolchildren in a rural area of the tropics

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.

Environmental determinants of total IgE among school children living in the rural Tropics: importance of geohelminth infections and effect of anthelmintic treatment

Background

The environmental factors that determine the elevated levels of polyclonal IgE observed in populations living in the Tropics are poorly understood but may include geohelminth infections. We investigated the association between geohelminth infections and total IgE levels in school children in rural tropical Ecuador, and assessed the effect on IgE of repeated anthelmintic treatments over a period of 12 months. The study was nested within a cluster-randomized study that randomized 68 schools to receive either 400 mg of albendazole every 2 months over a year or no treatment. We studied random samples of children completing follow-up and representing four groups stratified by the presence of geohelminth infection at baseline and treatment allocation. We measured levels of total IgE and anti-A. lumbricoides IgG (used as a measure of past and current geohelminth infectious exposure) in blood samples collected at the start of the study and after 12 months.

Results

We observed elevated levels of total IgE (compared to standard reference values) at the start of the study in this population of school children (geometric mean, 1,004 IU/mL, range 12 to 22,608 IU/mL)) and baseline IgE levels were strongly associated with parameters of geohelminth infection but not with age, nutritional and socioeconomic status. After 12 months, levels of IgE fell significantly in the treatment (by 35.1%) and no treatment (by 10.4%) groups, respectively, but the fall was significantly greater in the treatment group. Falls in IgE were independently associated with albendazole treatment, having a baseline geohelminth infection and with high baseline levels of anti-A. lumbricoides IgG. Increases in IgE at 12 months were associated with the presence of geohelminth infections and increasing levels of anti-A. lumbricoides IgG at 12 months independent of treatment allocation.

Conclusion

The data provide evidence that geohelminth infections are an important determinant of total IgE in school children in the rural Tropics and that periodic anthelmintic treatments over 12 months are associated with reductions in IgE. The failure of anthelmintic treatment to reduce IgE levels to that considered normal in industrialized countries may be attributed to continued exposure of children to geohelminths or to the effects of infections in early life in programming a long-lasting Th2-biassed immunity.

Risk factors for asthma and allergy associated with urban migration: background and methodology of a cross-sectional study in Afro-Ecuadorian school children in Northeastern Ecuador (Esmeraldas-SCAALA Study)

Background

Asthma and allergic diseases are becoming increasingly frequent in children in urban centres of Latin America although the prevalence of allergic disease is still low in rural areas. Understanding better why the prevalence of asthma is greater in urban migrant populations and the role of risk factors such as life style and environmental exposures, may be key to understand what is behind this trend.

Methods/design

The Esmeraldas-SCAALA (Social Changes, Asthma and Allergy in Latin America) study consists of cross-sectional and nested case-control studies of school children in rural and urban areas of Esmeraldas Province in Ecuador. The cross-sectional study will investigate risk factors for atopy and allergic disease in rural and migrant urban Afro-Ecuadorian school children and the nested case-control study will examine environmental, biologic and social risk factors for asthma among asthma cases and non-asthmatic controls from the cross-sectional study. Data will be collected through standardised questionnaires, skin prick testing to relevant aeroallergen extracts, stool examinations for parasites, blood sampling (for measurement of IgE, interleukins and other immunological parameters), anthropometric measurements for assessment of nutritional status, exercise testing for assessment of exercise-induced bronchospasm and dust sampling for measurement of household endotoxin and allergen levels.

Discussion

The information will be used to identify the factors associated with an increased risk of asthma and allergies in migrant and urbanizing populations, to improve the understanding of the causes of the increase in asthma prevalence and to identify potentially modifiable factors to inform the design of prevention programmes to reduce the risk of allergy in urban populations in Latin America.

Effect of albendazole treatments on the prevalence of atopy in children living in communities endemic for geohelminth parasites: a cluster-randomised trial

BACKGROUND

Epidemiological studies have shown inverse associations between geohelminth (intestinal helminth) infection and atopy, leading to the suggestion that geohelminths might protect against allergy. Periodic deworming of school children with anthelmintics is a widely implemented intervention and has raised concerns that such programmes could increase allergy. We investigated the effect of repeated anthelmintic treatments with albendazole over 12 months on the prevalence of atopy and clinical indices of allergy.

METHODS

We did a cluster-randomised controlled trial in schoolchildren from 68 rural schools. Children were randomly assigned by school to either albendazole (34 schools, 1164 children) every 2 months for 12 months, or to no intervention (34 schools, 1209 children). The intervention schools received a total of seven albendazole treatments. The primary outcome was atopy at 12 months (allergen skin-test reactivity), and analysis was by intention-to-treat for whole-school analyses and per protocol for children. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN61195515.

FINDINGS

Data for analysis were available for all schools and from 67.4% (784 of 1164) and 70.1% (848 of 1209) of children in albendazole and no-treatment groups, respectively. Albendazole treatment caused large reductions in geohelminth prevalence over the study period (adjusted odds ratio 0.13, 95% CI 0.09-0.19, p<0.001), but there was no evidence that treatment was associated with an increase in atopy prevalence (0.97, 0.68-1.39, p=0.862), or clinical allergy (wheeze, 1.07, 0.54-2.11, p=0.848) in the albendazole compared with the no-treatment group.

INTERPRETATION

We saw no increase in the prevalence of atopy or clinical allergy associated with albendazole treatment. Deworming programmes for schoolchildren are unlikely to be accompanied by an increase in allergy.

Relationship between bacille Calmette-Guérin vaccination, Mantoux test positivity, and geohelminth infection

To investigate the potential protective effects of Bacille Calmette-Guerin (BCG) vaccination scar and sensitization to tuberculin against geohelminth infections, we conducted a cross-sectional study among school age children in rural communities in Pichincha Province in Ecuador where BCG vaccination is routinely given at birth. A total of 944 children aged 8-14 years were evaluated for the presence of BCG scars and sensitization to tuberculin, and underwent faecal examination for geohelminth parasites. BCG scars were present in 88.2% of children and positive Mantoux tests were observed in 19.1% of children. Geohelminth prevalence was high with 70.3% infected with any parasite, 52.1% with Ascaris lumbricoides, 52.3% with Trichuris trichiura, 7.6% with Ancylostoma duodenale, and 3.0% with Strongyloides stercoralis. In multivariate analyses, the presence of BCG vaccine scars was not significantly associated with infections with any geohelminth parasite (adjusted odds ratio [AOR] = 0.74, 95% CI 0.43-1.28, P = 0.28), but an inverse association was observed for infections with S. stercoralis that was of borderline statistical significance (AOR = 0.38, 95% CI 0.15-1.00, P = 0.05). There were no associations between sensitization to tuberculin and infection with geohelminth parasites. The data provide little support for an important protective role of neonatal BCG vaccination or current mycobacterial sensitization against geohelminth infections.

Atopic phenotype is an important determinant of immunoglobulin E-mediated inflammation and expression of T helper cell type 2 cytokines to ascaris antigens in children exposed to ascariasis

Studies have shown a strong inverse relationship between atopy and geohelminth infection, indicating that atopy may protect against geohelminth infection. Resistance to ascariasis in atopic individuals may occur through greater immunoglobulin E-mediated responses and expression of T helper cell type 2 (Th2) cytokines to parasite antigens. To investigate the effect that atopy has on the immune response to Ascaris antigens, school-age children were recruited from rural schools in Ecuador. Immunologic variables were compared between children stratified by atopic and/or A. lumbricoides-infection status; the variables included cytokine expression by peripheral-blood mononuclear cells (PBMCs) and histamine release in response to Ascaris antigens. Atopic children had both greater frequencies of PBMCs expressing interleukin (IL)-4 and IL-5 and enhanced histamine release, compared with those in nonatopic children. Stratification by atopic and A. lumbricoides-infection status revealed the greatest histamine and Th2 cytokine responses in the stratum of atopic, noninfected children. Multivariate regression analyses showed significant effects for atopic status but not for infection status on Th2 cytokine expression and histamine release.

Risk factors for atopy among school children in a rural area of Latin America

BACKGROUND

Infection with common childhood infectious diseases including geohelminth infections may provide protection against the development of atopy and allergic disease. Few studies have investigated risk factors for atopy among children living in rural areas of Latin America.

OBJECTIVE

To identify risk factors associated with atopy among school-age children in a rural area of Latin America.

METHODS

Analytic cross-sectional study of school-age children conducted in seven rural schools in Pichincha Province in Ecuador. Detailed risk factor information was obtained by questionnaire, stool samples were collected for identification of geohelminth parasites, and Mantoux testing was performed to determine tuberculin sensitization.

RESULTS

A total of 1002 children from seven rural schools were recruited. The prevalence of geohelminth infections was high (70.1% were infected with at least one geohelminth parasite) and the prevalence of allergic sensitization was high (20.0% had evidence of aeroallergen sensitization). Factors associated with significant protection against atopy in multivariate analyses were the presence of overcrowding in the child's home, low socio-economic level, and infection with geohelminth parasites, and the protective effects of the three factors were statistically independent.

CONCLUSION

Low socio-economic level, overcrowding and geohelminth infection, are independently protective against atopy among school-age children living in a rural area of Latin America.

Geohelminth infections protect against severe inflammatory diarrhoea inchildren

We investigated the risk of severe inflammatory diarrhoea associated with geohelminth parasites in 1746 children attending a rural hospital in Ecuador from December 2000 to July 2002. Infections with geohelminths were strongly protective against the risk of severe inflammatory diarrhoea. Our findings suggest that geohelminth infections have important protective effects against enteroinvasive infections in young children.

Allergic symptoms, atopy, and geohelminth infections in a rural area of Ecuador

Geohelminth infections may affect the expression of allergic disease. To investigate the relationship between geohelminth infections, atopy, and symptoms of allergic disease, we studied 4433 schoolchildren from 71 schools in a rural tropical area in Ecuador. Information was collected on allergic symptoms, allergen skin test reactivity, and presence of geohelminth infections. Allergic symptoms were of low prevalence (2.1% had recent wheeze), but prevalence of skin test reactivity was relatively high (18.2%). The presence of geohelminth infections was protective against allergen skin test reactivity (odds ratio 0.62, 95% confidence interval 0.50-0.76, p < 0.001) and symptoms of exercise-induced wheeze (odds ratio 0.59, 95% confidence interval 0.40-0.87, p = 0.008) but not against other wheeze symptoms or symptoms of allergic rhinitis or atopic eczema. Infection intensity with Ascaris lumbricoides or Trichuris trichiura was associated with a reduction in the prevalence of allergen skin test reactivity but not with allergic symptoms. There was no evidence of interactions between geohelminth infection and allergen skin test reactivity on the risks of allergic symptoms. The results suggest that geohelminth infections do not explain the low prevalence of allergic symptoms in the study population.

Reduced risk of atopy among school-age children infected with geohelminth parasites in a rural area of the tropics

BACKGROUND

Childhood infections might protect against the expression of atopy. Geohelminths are among the most prevalent infections of childhood and might contribute to the low prevalence of allergic disease reported from rural areas of the tropics.

OBJECTIVE

We sought to establish whether geohelminth infections protect against atopy and to explore whether this protection is dependent on infection chronicity.

METHODS

The risk of atopy (measured by means of allergen skin test reactivity) associated with active geohelminth infections (measured by means of the presence of eggs in stool samples) or with chronic geohelminth infections (measured by means of high levels [>/=3564 IU/mL] of total serum IgE or the presence of detectable anti-Ascaris lumbricoides IgG4 antibodies) was investigated in an analytic cross-sectional study conducted among school-age children attending rural schools in Pichincha Province in Ecuador.

RESULTS

A total of 2865 children aged 5 to 19 years from 55 schools was examined. Active infection with any geohelminth and infections with A lumbricoides or Ancylostoma duodenale were associated with significant protective effects against allergen skin test reactivity. Children with the highest levels of total IgE or with anti-A lumbricoides IgG4 antibodies were protected against skin test reactivity also, and the protective effects of high IgE or anti-A lumbricoides IgG4 and or active geohelminth infections were statistically independent.

CONCLUSION

Active infections with geohelminth parasites and the presence of serologic markers of chronic infections (high levels of total serum IgE or anti-A lumbricoides IgG4) are independent protective factors against allergen skin test reactivity among school-age children living in an endemic region of the rural tropics.

Albendazole treatment of children with ascariasis enhances the vibriocidal antibody response to the live attenuated oral cholera vaccine CVD 103-HgR

Because concurrent infections with geohelminth parasites might impair the immune response to oral vaccines, we studied the vibriocidal antibody response to the oral cholera vaccine CVD 103-HgR in children infected with Ascaris lumbricoides and investigated the effect of albendazole pretreatment on the postvaccination response. Children with ascariasis were randomized to receive either 2 sequential doses of 400 mg of albendazole or placebo. After the second dose, CVD 103-HgR was given, and serum vibriocidal antibody levels were measured before and 10 days after vaccination. Postvaccination rates of seroconversion were greater in the treatment group that received albendazole (P=.06). Significantly greater rates of seroconversion and geometric mean titer were observed in the albendazole group in subjects with non-O ABO blood groups. A significant association was observed between vibriocidal seroconversion rates and treatment group, suggesting that A. lumbricoides infections impair the immune response to oral cholera vaccine, particularly in subjects of non-O blood groups.

Human infection with Ascaris lumbricoides is associated with a polarized cytokine response

To define the cytokine response to Ascaris lumbricoides infection, the cellular immune response to adult and larval-stage Ascaris antigens in young adults with moderate infection intensities (n=73) was compared with that of a group of uninfected control subjects (n=40). A. lumbricoides-infected subjects had significantly greater lymphoproliferative responses to adult and larval-stage antigens, compared with uninfected control subjects (P<.01). The frequencies of parasite antigen-stimulated peripheral blood mononuclear cell (PBMC)-expressing interleukin (IL)-4 and IL-5 were significantly greater in the infected group (P<.001), whereas the frequencies of IL-10- and interferon-gamma-expressing PBMC were similar in the 2 groups studied. The ratios of Th2 to Th1 cytokine frequencies were significantly elevated in the infected group, compared with those in uninfected subjects, as was IL-5 protein production by PBMC stimulated with adult (P<.05) and L3/L4 stage (P<.001) antigens. Analysis of these data indicates that A. lumbricoides infections in endemic regions are associated with a highly polarized type 2 cytokine response.

Macrofilaricidal effects of chloroquine on adult Onchocerca volvulus by local infiltration of palpable onchocercal nodules

The macrofilaricidal effects of local infiltration of high concentrations of chloroquine into the capsule of onchocercal nodules on adult worms of Onchocerca volvulus was determined. Six weeks post infiltration, histological examination of single nodules showed all adult worms to be dead. With nodule conglomerates, there was localized action of chloroquine only on the adult worms in the infiltrated nodule, with no diffusion of the drug to adjacent nodules. Chloroquine infiltration of young, recently formed nodules to reduce the adult worm load of infected individuals may be an alternative method to costly nodulectomy.

Evaluation of a direct immunofluorescent antibody (DIFMA) test using Leishmania genus-specific monoclonal antibody in the routine diagnosis of cutaneous leishmaniasis

A direct immunofluorescent antibody (DIFMA) test using a Leishmania genus-specific monoclonal antibody was evaluated in the routine diagnosis of cutaneous leishmaniasis (CL) in Ecuador. This test was compared with the standard diagnostic techniques of scrapings, culture and histology. Diagnostic samples were taken from a total of 90 active dermal ulcers from patients from areas of Ecuador known to be endemic for cutaneous leishmaniasis. DIFMA was positive in all lesions. It was shown to be significantly superior to standard diagnostic methods either alone or in combination. The sensitivity of DIFMA did not diminish with chronicity of lesions. This test proved to be extremely useful in the routine diagnosis of CL because it is highly sensitive, is easy to use and produces rapid results.

Placebo controlled treatment of Ecuadorian cutaneous leishmaniasis

Pentavalent antimony has been considered to be the standard treatment for leishmaniasis, but more recently, the orally administrable agent allopurinol ribonucleoside has been the subject of several clinical trials. In this study, these two agents were evaluated in patients with Ecuadorian cutaneous leishmaniasis. Patients were randomly assigned to the two treatment groups. The mean reduction in lesion size for the 28 patients treated with Pentostam (20 mg Sb/kg/day intramuscularly for 20 days) was 61%, 23%, and 11% after one, two, and three weeks, respectively. There was a wide range in the individual values, and some lesions markedly enlarged in the first week of therapy. An initially healed lesion was defined as one that had greater than 80% re-epithelialized by the 1.5-month post-treatment followup. All Pentostam patients demonstrated this degree of lesion resolution (100% initial healing rate), but one patient showed evidence of relapse at the three month followup resulting in a 96% complete healing rate for the 12 month observation period. Patients in the untreated control group demonstrated a strikingly high rate of healing with 9 of 12 patients having re-epithelialized all lesions after 1.5 months observation (75% initial healing rate). The mean reduction in lesion size for the untreated patients was 56%, 29%, and 25% after one, two, and three weeks, respectively. Twenty-one patients received allopurinol ribonucleoside (1,500 mg QID) plus probenecid (500 mg QID) for 28 days. Lesions in nine of these patients were healed at the time of the 1.5 month followup (41% healing rate).(ABSTRACT TRUNCATED AT 250 WORDS)

Chagas disease in Ecuador: a sylvatic focus in the Amazon region

A sylvatic focus of Chagas disease is reported in the Amazon region of Ecuador (provinces of Napo and Sucumbios). During 1987-1989, 10 cases of acute infection were diagnosed by direct visualization of Trypanosoma cruzi in peripheral blood smears during routine malaria checks. Also in that region, three triatomine bugs, Rhodnius pictipes, Rhodnius robustus and Panstrongylus geniculatus were found naturally infected with T. cruzi suggesting that the human cases represent an autochthonous focus of active transmission.

Human cutaneous leishmaniasis in Ecuador: identification of parasites by enzyme electrophoresis

Twenty-six strains of Leishmania were isolated from cutaneous lesions in humans in 3 different geographical areas of Ecuador. The species were identified by enzyme electrophoresis as Leishmania braziliensis, L. panamensis, L. guyanensis, L. mexicana, and L. amazonensis.