Farming exposure in childhood, exposure to markers of infections and the development of atopy in rural subjects

Effect of Heat Pasteurization and Sterilization on Milk Safety, Composition, Sensory Properties, and Nutritional Quality

Milk pasteurization and sterilization by heat treatment have an exciting history, which followed steady steps. The main aim of these treatments is to extend the shelf life of milk by destroying pathogenic and milk spoilage bacteria. With developments in pasteurization techniques, the assurance of milk safety, and extended shelf life, pasteurized bovine milk has become a staple food, especially in Western diets. However, some concerns have recently been raised about the effect of pasteurization on the sensory properties and nutritional quality of milk, and alternative methods, such as high-pressure processing, are being investigated. The primary purpose of milk pasteurization and sterilization is summarized in this review article. The associated changes that affect the compositional, sensory, and nutritional quality of milk are discussed, with particular emphasis on protein structure and function. The review is concluded by considering alternative methods, their advantages and limitations, along with future prospects.

Residential greenness, respiratory symptoms and lung function in children, adolescents and adults with asthma: A cross-sectional study

BACKGROUND

We hypothesize that green areas within cities affect the respiratory symptoms of individuals with asthma, but this effect may not be the same for all age groups.

OBJECTIVE

Evaluate whether there is an association between the percentage of green area close to the residence and asthma outcomes, stratified by age group.

METHODS

We included individuals with asthma from all 42 public health facilities in a Brazilian municipality with 400,000 inhabitants. Two independent researchers, blinded to clinical information regarding asthma, measured the extent of green area around the residence of study volunteers using satellite images. The primary outcome was the severity of respiratory symptoms. The secondary outcome was the presence of airway obstruction in the spirometry test carried out at the study visit. Adjusted regression analyzes evaluated whether the percentage of green area close to the residence was associated with asthma outcomes.

RESULTS

In children-adolescents (n = 322), greater density of green area was associated with a greater frequency of uncontrolled asthma symptoms [OR 1.25, 95CI (1.02-1.54)]. In adults (n = 966), more greenness was associated with a lower frequency of uncontrolled asthma symptoms [OR 0.90, 95CI (0.81-0.99)] and a lower frequency of airway obstruction [OR 0.86, 95CI (0.78-0.96)].

CONCLUSIONS

The extent of green areas close to the residence is associated with asthma morbidity, but the direction of this association differs between child-adolescents and adults. Studies need to clarify why the effect of vegetation cover on asthma symptoms differs between children-adolescents and adults.

Helicobacter pylori Infection Does Not Protect Against Allergic Diseases: Evidence From a Pediatric Cohort From Northern Sardinia, Italy

BACKGROUND

The "hygiene hypothesis" states that reduced exposure to microbial antigens due to an excessively hygienic environment can increase the risk of developing autoimmune diseases, including atopic disorders and asthma. In recent decades, there has been a progressive decline in the prevalence of numerous microorganisms following improved hygienic-sanitary conditions. More specifically, several studies reported an inverse association between the reduction in Helicobacter pylori infection and the rise of asthma and allergic disorders.

AIM

To evaluate the prevalence of atopic disorders in a pediatric population in relation to seropositivity against H. pylori.

METHODS

Children from Northern Sardinia, Italy, referred to the local Children's Hospital for any reason, were investigated to identify risk factors, especially H. pylori infection, associated with atopic disorders. A validated questionnaire, including demographics, house size, history of breastfeeding, residence, school or daycare center attendance, exposure to animals, and a defined diagnosis of atopy-including asthma-was filled out by a trained pediatrician according to parents' answers and child records. A blood sample was collected from each participant and immunoglobulin G against H. pylori was assessed by a locally validated ELISA test.

RESULTS

The seroprevalence of H. pylori infection was 11.7% among 492 children (240 females). Thirty-two children had a confirmed diagnosis of asthma and 12 of allergy. No one child showed both conditions. Statistically significant differences in H. pylori seropositivity were not detected between children with or without atopy (8.4% vs. 12.6; p = 0.233). Although atopic disorders were more frequent in children exposed to traditional atopic risk factors, none of them showed to be significant after adjusting for all covariates.

CONCLUSIONS

Serologically assessed H. pylori infection was not significantly associated with a reduced risk of atopic diseases in children.

Toxoplasma gondii Antibodies in Raw Milk and Sera of Cows in China

Toxoplasma gondii is a worldwide food-borne protozoa that has harmful influences on animal and human health. Raw milk containing T. gondii has been considered as one of the possible infectious sources for humans. Although China is one of the world’s leading milk consumers, there is still no study to investigate the seroprevalence of T. gondii in raw cow milk in China; especially for cows in rural areas. Thus, we conducted this study to examine the specific anti-T. gondii IgG-antibody in the raw milk and sera of domestic cows in China. In total, 894 cows were randomly selected from rural areas in northeastern China. The positive rate of T. gondii in the milk and serum samples were 6.38% (57/894) and 7.16% (64/894), respectively. Moreover, a history of abortion (OR = 2.03, 95% CI: 1.11–3.72, p = 0.022) was identified as the only risk factor for T. gondii infection in the studied cows. This study investigated the seroprevalence of T. gondii in the raw milk and sera of cows in China; it provided timely and useful data for public health and food safety, especially in rural areas.

Epithelial barrier hypothesis: Effect of the external exposome on the microbiome and epithelial barriers in allergic disease

Environmental exposure plays a major role in the development of allergic diseases. The exposome can be classified into internal (e.g., aging, hormones, and metabolic processes), specific external (e.g., chemical pollutants or lifestyle factors), and general external (e.g., broader socioeconomic and psychological contexts) domains, all of which are interrelated. All the factors we are exposed to, from the moment of conception to death, are part of the external exposome. Several hundreds of thousands of new chemicals have been introduced in modern life without our having a full understanding of their toxic health effects and ways to mitigate these effects. Climate change, air pollution, microplastics, tobacco smoke, changes and loss of biodiversity, alterations in dietary habits, and the microbiome due to modernization, urbanization, and globalization constitute our surrounding environment and external exposome. Some of these factors disrupt the epithelial barriers of the skin and mucosal surfaces, and these disruptions have been linked in the last few decades to the increasing prevalence and severity of allergic and inflammatory diseases such as atopic dermatitis, food allergy, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, and asthma. The epithelial barrier hypothesis provides a mechanistic explanation of how these factors can explain the rapid increase in allergic and autoimmune diseases. In this review, we discuss factors affecting the planet's health in the context of the 'epithelial barrier hypothesis,' including climate change, pollution, changes and loss of biodiversity, and emphasize the changes in the external exposome in the last few decades and their effects on allergic diseases. In addition, the roles of increased dietary fatty acid consumption and environmental substances (detergents, airborne pollen, ozone, microplastics, nanoparticles, and tobacco) affecting epithelial barriers are discussed. Considering the emerging data from recent studies, we suggest stringent governmental regulations, global policy adjustments, patient education, and the establishment of individualized control measures to mitigate environmental threats and decrease allergic disease.

Detection of Specific IgG-Antibodies Against Toxoplasma gondii in the Serum and Milk of Domestic Donkeys During Lactation in China: A Potential Public Health Concern

Toxoplasma gondii is a worldwide zoonotic protozoan. Donkeys are often susceptible to many pathological agents, acting as carriers of pathogens for other animal species and humans. However, data on the prevalence of T. gondii in donkeys during lactation and on the status of antibodies against T. gondii in donkey milk are lacking. A cross-sectional study evaluated the variation of the anti-T. gondii antibodies in the blood and milk of domestic donkeys during lactation. A total of 418 domestic donkeys were randomly selected from the Shandong province, eastern China from January 2019 to March 2020. The anti-T. gondii antibodies were found in 11.72% (49/418) serum and 9.81% (41/418) milk samples using a commercial ELISA kit, respectively. There was a very high consistency between the serum and milk (Spearman’s coefficient = 0.858, p-value < 0.0001 and Kendall’s tau = 0.688, p-value < 0.0001), particularly at the 45th to 60th day of lactation. The present results of the statistical analysis showed that the history of abortion (p = 0.026; adjusted OR = 2.20; 95% CI: 1.15–4.20) and cat in the house (p = 0.008; adjusted OR = 2.36; 95% CI: 1.26–4.44) were significantly associated with T. gondii infection in the domestic donkeys. This is the first report to detect antibodies against T. gondii in donkey milk in China. These results indicate a potential risk of humans contracting the infection through the consumption of raw milk from the naturally infected donkeys.

The intersect of genetics, environment, and microbiota in asthma-perspectives and challenges

In asthma, a significant portion of the interaction between genetics and environment occurs through microbiota. The proposed mechanisms behind this interaction are complex and at times contradictory. This review covers recent developments in our understanding of this interaction: the "microbial hypothesis" and the "farm effect"; the role of endotoxin and genetic variation in pattern recognition systems; the interaction with allergen exposure; the additional involvement of host gut and airway microbiota; the role of viral respiratory infections in interaction with the 17q21 and CDHR3 genetic loci; and the importance of in utero and early-life timing of exposures. We propose a unified framework for understanding how all these phenomena interact to drive asthma pathogenesis. Finally, we point out some future challenges for continued research in this field, in particular the need for multiomic integration, as well as the potential utility of asthma endotyping.

Latent Toxoplasma gondii infections are associated with elevated biomarkers of inflammation and vascular injury

BACKGROUND

Toxoplasma gondii is a protozoan parasite that infects cats as definitive hosts and other warm-blooded animals including humans as intermediate hosts. It forms infectious cysts in the brain, muscle and other tissues establishing life-long latent infection. Approximately 10% of the US population is infected. While latent infections are largely asymptomatic, they are associated with neurological deficits and elevated risks of neuropsychiatric diseases.

METHODS

This cross-sectional epidemiological study investigated associations of T. gondii infections with biomarkers of inflammation and vascular injury: soluble intercellular adhesion molecule 1 (ICAM-1), soluble vascular cell adhesion molecule 1 (VCAM-1), C-reactive protein (CRP), and serum amyloid A (SAA). Serum samples from 694 adults in the Raleigh-Durham-Chapel Hill, North Carolina metropolitan area were tested for IgG antibody response to T. gondii, and for the above biomarkers using commercially available assays.

RESULTS

T. gondii seroprevalence rate in this sample was 9.7%. Seropositivity was significantly associated with 11% (95% confidence limits 4, 20%) greater median levels of VCAM-1 (p = 0.003), and marginally significantly with 9% (1, 17%), and 36% (1, 83%) greater median levels of ICAM-1, and CRP, respectively (p = 0.04 for each) after adjusting for sociodemographic and behavioral covariates, while the 23% (- 7, 64%) adjusted effect on SAA was not statistically significant (p = 0.15).

CONCLUSIONS

Latent infections with T. gondii are associated with elevated biomarkers of chronic inflammation and vascular injury that are also known to be affected by ambient air pollution.

Environmental factors associated with allergy in urban and rural children from the South African Food Allergy (SAFFA) cohort

BACKGROUND

The prevalence of allergic diseases differs in urban and rural populations.

OBJECTIVE

We sought to assess associations between environmental and dietary factors with allergic diseases in urban and rural South African children.

METHODS

Toddlers aged 12 to 36 months were assessed for food allergen and aeroallergen sensitization, atopic dermatitis, allergic rhinitis, asthma, and challenge-proved food allergy. Information was collected on family history of allergic diseases, household size, socioeconomic status, delivery mode, antibiotic and probiotic use, exposure to fermented and unpasteurized milk, antihelminth treatment, sunlight exposure, pet and farm animal exposure, cigarette smoke, and household cooking and heating fuels. Antenatal exposures to pets, livestock, and cigarette smoke were assessed. A subsection completed questions on consumption of fruits and vegetables, fast foods, soft drinks/fruit juices, and fried/microwaved meat.

RESULTS

Risk and protective factors differed between urban and rural settings. Exposure to farm animals in infants and their mothers during pregnancy was protective against allergic outcomes in the rural population. Consumption of unpasteurized milk is uncommon in this group of rural children and is unlikely to be an important factor in rural protection. In urban children birth by cesarean section is associated with food allergy, and consumption of fermented milk products is associated with reduced asthma and atopic dermatitis. In both cohorts antenatal maternal smoking and environmental smoking exposure were predominantly associated with asthma, and consumption of fast foods and fried meats were associated with allergy.

CONCLUSION

In this rural environment exposure to livestock is the strongest protective factor. In urban communities, where animal contact is rare, risk factors include cesarian section, and protective factors include consumption of fermented milk products. Modifiable risk factors urgently require interventions to prevent increasing allergy rates in countries undergoing rapid urbanization.

Recent Trends in Unpasteurized Fluid Milk Outbreaks, Legalization, and Consumption in the United States

Introduction: Determining the potential risk of foodborne illness has become critical for informing policy decisions, due to the increasing availability and popularity of unpasteurized (raw) milk.

Methods: Trends in foodborne illnesses reported to the Centers for Disease Control in the United States from 2005 to 2016 were analyzed, with comparison to state legal status and to consumption, as estimated by licensing records.

Results: The rate of unpasteurized milk-associated outbreaks has been declining since 2010, despite increasing legal distribution. Controlling for growth in population and consumption, the outbreak rate has effectively decreased by 74% since 2005.

Discussion: Studies of the role of on-farm food safety programs to promote the further reduction of unpasteurized milk outbreaks should be initiated, to investigate the efficacy of such risk management tools.

Early-life farm exposures and adult asthma and atopy in the Agricultural Lung Health Study

BACKGROUND

Previous studies, mostly from Europe, suggest that early-life farming exposures protect against childhood asthma and allergy; few data exist on asthma and allergy in adults.

OBJECTIVE

We sought to examine associations between early-life farming exposures and current asthma and atopy in an older adult US farming population.

METHODS

We analyzed data from 1746 farmers and 1555 spouses (mean age, 63) from a case-control study nested within the Agricultural Health Study. Current asthma and early-life farming exposures were assessed via questionnaires. We defined atopy based on specific IgE > 0.70 IU/mL to at least 1 of 10 allergens measured in blood. We used logistic regression, adjusted for age, sex, race, state (Iowa or North Carolina), and smoking (pack years), to estimate associations between early-life exposures and asthma (1198 cases and 2031 noncases) or atopy (578 cases and 2526 noncases).

RESULTS

Exposure to the farming environment in utero and in early childhood had little or no association with asthma but was associated with reduced odds of atopy. The strongest association was seen for having a mother who performed farm activities while pregnant (odds ratio, 0.60; 95% CI, 0.48-0.74) and remained significant in models with correlated early-life exposures including early childhood farm animal contact and raw milk consumption.

CONCLUSIONS

In a large US farming population, early-life farm exposures, particularly maternal farming activities while pregnant, were strongly associated with reduced risk of atopy in adults. These results extend previous work done primarily on childhood outcomes and suggest that protective associations of early-life farming exposures on atopy endure across the life course.

Helicobacter, Hygiene, Atopy, and Asthma

The hygiene hypothesis links environmental and microbial exposures in early life to the prevalence of atopy, allergy, and asthma. Helicobacter pylori infection is typically acquired in childhood and acquisition of the infection is associated with poor household hygiene. Some population surveys have shown an inverse association between H. pylori infection and atopy, allergy, and asthma leading to the suggestion that H. pylori infection may be protective against disease; others consider it simply a biomarker for poor household hygiene. We review the relevant surveys, cohort studies, meta-analyses, and studies testing the protective hypothesis. Overall, the results of surveys and cohort studies are inconsistent, whereas meta-analyses show a significant but weak inverse correlation. In contrast, studies directly testing the protection hypothesis in relation to asthma in populations with poor hygiene and low H. pylori prevalence failed to confirm a protective effect. H. pylori is a major cause of human disease including chronic gastritis, peptic ulcer, and gastric malignancies. H. pylori infections most likely serve as a biomarker for poor hygienic conditions in childhood. We conclude that while synergistic interactions between environmental factors in childhood are important determinants of the pathogenesis of atopy, allergy, and asthma; H. pylori is inversely related to good hygiene and thus it's presence serves as a biomarker rather than for a specific prevention role for H. pylori or H. pylori antigens.

Outcomes in Patients with Helicobacter pylori Undergoing Laparoscopic Sleeve Gastrectomy

BACKGROUND

In vertical sleeve gastrectomy (VSG), the majority of the stomach is resected and much of the tissue colonized with Helicobacter pylori and the bulk of acid producing cells are removed. In addition, the effect of H. pylori colonization of the stomach of patients undergoing stapling procedures is unclear. As a result, the need for detection and treatment of H. pylori in patients undergoing VSG is unknown.

METHODS

Four hundred and eighty patients undergoing VSG are the subject of this study. Three surgeons at a single institution performed the procedures. The remnant stomach was sent to pathology and tested for the presence of H. pylori using immunohistochemistry. All patients were discharged on proton pump inhibitors.

RESULTS

Of the 480 patients who underwent VSG, 52 were found to be H. pylori positive based on pathology. There was no statistically significant difference in age (p = 0.77), sex (p = 0.48), or BMI (p = 0.39) between the groups. There were 17 readmissions post-op. Five of these were in the H. pylori positive cohort. Six of these complications were classified as severe (anastomotic leak, intra-abdominal collection, or abscess), with two in the H. pylori positive cohort (Table 1). There was no statistically significant difference in the severe complication rates between the two groups (p = 0.67). There were no readmissions for gastric or duodenal ulceration or perforation.

CONCLUSIONS

Our data suggests that there is no increase in early complications in patients with H. pylori undergoing VSG. If these findings are confirmed in a long-term follow-up, it would mean that preoperative H. pylori screening in patients scheduled for VSG is not necessary.

The microbial environment and its influence on asthma prevention in early life

There is accumulating evidence to suggest that the environmental microbiome plays a significant role in asthma development. The very low prevalence of asthma in populations highly exposed to microbial environments (farm children and Amish populations) highlights its preventive potential. This microbial diversity might be necessary to instruct a well-adapted immune response and regulated inflammatory responses to other inhaled and ingested environmental elements, such as allergens, particles, and viruses. Like the internal gut microbiome, which is increasingly recognized as an important instructor of immune maturation, the external environmental microbiome might shape immune responses on the skin, airway mucosal surfaces, and potentially also the gut early in life. The diversity of the external microbial world will ensure that of the many maladapted pathways leading to asthma development, most, if not all, will be counterbalanced. Likewise, important contributors to asthma, such as allergen sensitization and allergic manifestations early in life, are being suppressed. Thus the facets of innate immunity targeted by microbes and their compounds and metabolites might be the master switch to asthma and allergy protection, which has been found in environments rich in microbial exposures.

Exposure to 'farming' and objective markers of atopy: a systematic review and meta-analysis

There is growing interest in the 'farm effect' on the spectrum of allergy. Evidence concerning the farm effect on asthma, eczema, and allergic rhinitis has been systematically synthesized, but without a specific focus on objective markers of sensitization. This focus is important, as farm exposures may be related to allergy but not to non-allergic phenotypes of disease. We aimed to systematically review and meta-analyse literature that has investigated associations between farm exposure at any age and objective measures of atopy, that is serum IgE or skin prick tests results. Using predefined inclusion and exclusion criteria, we identified 29 articles for review. IgE levels were measured in either childhood or adulthood by eighteen studies, while skin prick testing was performed in sixteen studies. Newcastle-Ottawa Scale quality assessments indicated that the majority of these studies demonstrated a representative sample of selected participants. Due to significant heterogeneity in study measures and methodology between studies, only few were meta-analysed. This meta-analysis showed a significant protective effect of farm exposure before 1 year of life on allergic sensitization (OR = 0.60 [0.52-0.70]). Farm exposure during childhood was also associated with a reduced risk of sensitization to cat or timothy (OR = 0.60 [0.51-0.70]; OR=0.46 [0.41-0.51]). Studies investigating the effect of farm exposure in adult life could not be meta-analysed, and their results were inconsistent. Insufficient studies investigated food sensitization as an outcome to allow synthesis. The majority of studies included in this review investigated childhood farm exposure, finding evidence to support a protective childhood 'farm effect' against subsequent atopy. There is inconsistent evidence on the association between farm exposure in adulthood and allergic sensitization. Further studies are needed to tease out the exact exposures and timing associated with farming environments that protect against allergic disease.

Helicobacter pylori infection and atopic diseases: is there a relationship? A systematic review and meta-analysis

AIM

To review and conduct a meta-analysis of the existing literature on the relationship between Helicobacter pylori (H. pylori), atopy and allergic diseases.

METHODS

Studies published in English assessing the prevalence of atopy and/or allergic diseases in patients with H. pylori infection and the prevalence of H. pylori infection in patients with atopy and/or allergic diseases were identified through a MEDLINE search (1950-2014). Random-effect model was used for the meta-analysis.

RESULTS

Pooled results of case-control studies showed a significant inverse association of H. pylori infection with atopy/allergic disease or with exclusively atopy, but not with allergic disease, whereas pooled results of cross-sectional studies showed only a significant association between allergic disease and H. pylori infection.

CONCLUSION

There is some evidence of an inverse association between atopy/allergic diseases and H. pylori infection, although further studied are needed.

Increased regulatory T-cell numbers are associated with farm milk exposure and lower atopic sensitization and asthma in childhood

BACKGROUND

European cross-sectional studies have suggested that prenatal and postnatal farm exposure decreases the risk of allergic diseases in childhood. Underlying immunologic mechanisms are still not understood but might be modulated by immune-regulatory cells early in life, such as regulatory T (Treg) cells.

OBJECTIVE

We sought to assess whether Treg cells from 4.5-year-old children from the Protection against Allergy: Study in Rural Environments birth cohort study are critical in the atopy and asthma-protective effect of farm exposure and which specific exposures might be relevant.

METHODS

From 1133 children, 298 children were included in this study (149 farm and 149 reference children). Detailed questionnaires until 4 years of age assessed farming exposures over time. Treg cells were characterized as upper 20% CD4(+)CD25(+) forkhead box protein 3 (FOXP3)(+) (intracellular) in PBMCs before and after stimulation (with phorbol 12-myristate 13-acetate/ionomycin or LPS), and FOXP3 demethylation was assessed. Atopic sensitization was defined by specific IgE measurements; asthma was defined by a doctor's diagnosis.

RESULTS

Treg cells were significantly increased in farm-exposed children after phorbol 12-myristate 13-acetate/ionomycin and LPS stimulation. Exposure to farm milk was defined as a relevant independent farm-related exposure supported by higher FOXP3 demethylation. Treg cell (upper 20% CD4(+)CD25(+), FOXP3(+) T cells) numbers were significantly negatively associated with doctor-diagnosed asthma (LPS stimulated: adjusted odds ratio, 0.26; 95% CI, 0.08-0.88) and perennial IgE (unstimulated: adjusted odds ratio, 0.21; 95% CI, 0.08-0.59). Protection against asthma by farm milk exposure was partially mediated by Treg cells.

CONCLUSIONS

Farm milk exposure was associated with increased Treg cell numbers on stimulation in 4.5-year-old children and might induce a regulatory phenotype early in life, potentially contributing to a protective effect for the development of childhood allergic diseases.

Asthma and allergies: is the farming environment (still) protective in Poland? The GABRIEL Advanced Studies

BACKGROUND

Evidence exists that a farming environment in childhood may provide protection against atopic respiratory disease. In the GABRIEL project based in Poland and Alpine regions of Germany, Austria and Switzerland, we aimed to assess whether a farming environment in childhood is protective against allergic diseases in Poland and whether specific exposures explain any protective effect.

METHODS

In rural Poland, 23 331 families of schoolchildren completed a questionnaire enquiring into farming practices and allergic diseases (Phase I). A subsample (n = 2586) participated in Phase II involving a more detailed questionnaire on specific farm exposures with objective measures of atopy.

RESULTS

Farming differed between Poland and the Alpine centres; in the latter, cattle farming was prevalent, whereas in Poland 18% of village farms kept ≥1 cow and 34% kept ≥1 pig. Polish children in villages had lower prevalences of asthma and hay fever than children from towns, and in the Phase II population, farm children had a reduced risk of atopy measured by IgE (aOR = 0.72, 95% CI 0.57, 0.91) and skin prick test (aOR = 0.65, 95% CI 0.50, 0.86). Early-life contact with grain was inversely related to the risk of atopy measured by IgE (aOR = 0.66, 95% CI 0.47, 0.92) and appeared to explain part of the farming effect.

CONCLUSION

While farming in Poland differed from that in the Alpine areas as did the exposure-response associations, we found in communities engaged in small-scale, mixed farming, there was a protective farming effect against objective measures of atopy potentially related to contact with grain or associated farm activities.

Consumption of unpasteurized milk and its effects on atopy and asthma in children and adult inhabitants in rural Poland

BACKGROUND

Consumption of unpasteurized cow's milk has been identified as a possible protective factor for atopy and asthma. Most studies have been conducted among children and in farming populations. We investigated the effects of consumption of unpasteurized milk in early life on atopy, asthma, and rhinitis in village and town inhabitants in a region of Poland and assessed whether any protective effects of milk consumption differed according to place of residence and farming status.

METHODS

We surveyed the inhabitants (aged >5 years) of a small town and seven nearby villages in southwest Poland (n = 1700, response rate 88%). Participants (or their parents for those <16 years of age) completed a questionnaire on farm exposures and symptoms of asthma and rhinitis. In particular, information was collected on unpasteurized milk consumption in early life. Atopy was assessed using skin prick tests.

RESULTS

Consumption of unpasteurized milk in the first year of life was inversely associated with atopy and asthma both among town and village inhabitants - town: adjusted odds ratio (aOR) for atopy 0.46 [95% confidence interval (CI) 0.37-0.52] asthma 0.51 (0.32-0.74); villages: atopy 0.59 (0.44-0.70) and asthma 0.59 (0.42-0.74). For atopy, the protective effect was more clearly seen among nonfarmers (0.42; 0.34-0.46) than in farmers (0.82; 0.54-1.11). For doctor-diagnosed hay fever and current rhinitis symptoms, the protective effect was only observed among town inhabitants and/or nonfarmers.

CONCLUSIONS

Early-life exposure to unpasteurized milk may protect against atopy, asthma, and related conditions, independently of place of residence and farming status, and in both children and adults.

The immunomodulatory properties of Helicobacter pylori confer protection against allergic and chronic inflammatory disorders

Chronic infection with the gastric bacterial pathogen Helicobacter pylori causes gastritis and predisposes carriers to a high risk of developing gastric and duodenal ulcers, gastric cancer, and gastric lymphoma, but has also recently been shown to protect against certain allergic and chronic inflammatory disorders. The immunomodulatory properties that allow the bacteria to persist for decades in infected individuals in the face of a vigorous, yet ultimately non-protective, innate, and adaptive immune response may at the same time confer protection against allergies, asthma, and inflammatory bowel diseases. Experimental evidence from mouse models suggests that H. pylori has evolved to skew the adaptive immune response toward immune tolerance rather than immunity, which promotes persistent infection on the one hand, and inhibits auto-aggressive and allergic T-cell responses on the other. Regulatory T-cells mediating peripheral immune tolerance have emerged as key cellular players in facilitating persistent infection as well as protection from allergies, in both observational studies in humans and experimental work in mice. Recent data suggest that H. pylori actively targets dendritic cells to promote tolerance induction. The findings discussed in this review raise the possibility of harnessing the immunomodulatory properties of H. pylori for the prevention and treatment of allergic and auto-immune diseases, and also provide new insights relevant for H. pylori-specific vaccine development.

A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes

Pasteurization of milk ensures safety for human consumption by reducing the number of viable pathogenic bacteria. Although the public health benefits of pasteurization are well established, pro-raw milk advocate organizations continue to promote raw milk as "nature's perfect food." Advocacy groups' claims include statements that pasteurization destroys important vitamins and that raw milk consumption can prevent and treat allergies, cancer, and lactose intolerance. A systematic review and meta-analysis was completed to summarize available evidence for these selected claims. Forty studies assessing the effects of pasteurization on vitamin levels were found. Qualitatively, vitamins B12 and E decreased following pasteurization, and vitamin A increased. Random effects meta-analysis revealed no significant effect of pasteurization on vitamin B6 concentrations (standardized mean difference [SMD], -2.66; 95% confidence interval [CI], -5.40, 0.8; P = 0.06) but a decrease in concentrations of vitamins B1 (SMD, -1.77; 95% CI, -2.57, -0.96; P < 0.001), B2 (SMD, -0.41; 95% CI, -0.81, -0.01; P < 0.05), C (SMD, -2.13; 95% CI, -3.52, -0.74; P < 0.01), and folate (SMD, -11.99; 95% CI, -20.95, -3.03; P < 0.01). The effect of pasteurization on milk's nutritive value was minimal because many of these vitamins are naturally found in relatively low levels. However, milk is an important dietary source of vitamin B2, and the impact of heat treatment should be further considered. Raw milk consumption may have a protective association with allergy development (six studies), although this relationship may be potentially confounded by other farming-related factors. Raw milk consumption was not associated with cancer (two studies) or lactose intolerance (one study). Overall, these findings should be interpreted with caution given the poor quality of reported methodology in many of the included studies.

Can farm milk consumption prevent allergic diseases?

Cow's milk is an important part of human diet and a source of food allergy for some individuals. Medical guidance strongly discourages consumption of raw milk because of the known health risk associated with pathogenic bacteria present in unpasteurized milk. Despite these risks there is a growing body of epidemiological evidence suggesting that consumption of unprocessed cow's milk does not increase but rather decreases the risk of asthma, hay fever and atopic sensitisation. The article reviews the epidemiological literature and discusses components of unprocessed milk potentially responsible for this protection. It focuses on the role of bacteria in raw milk, the fatty acid profile, whey proteins and finally the role of allergens in milk. Although the epidemiological evidence consistently suggest a protective role of unprocessed cow's milk consumption on the development of asthma, hay fever and atopic sensitization the underlying mechanisms are not yet understood and the consumption of raw milk cannot be recommended as a preventive measure for allergic diseases.

Allergic rhinitis: an update on disease, present treatments and future prospects

Allergic rhinitis (AR) is an inflammation of nasal mucosa mediated by IgE-associated processes occurring independently, or concurrently with asthma. AR is characterized by sensitization-formation and expression of antigen specific IgE, followed by inflammation in two phases. The early phase response involves cross linking of IgE molecules leading to degranulation of mast cells and release of preformed mediators such as histamine and tryptase, or newly synthesized mediators such as prostaglandins and leukotrienes. The late phase response is predominated by the presence of eosinophils, lymphocytes, cytokines, and adhesion molecules. Newer insights reveal that the whole phenomenon of immunological inflammation is intricately knit with neural pathways, which strongly influence the process. Furthermore, AR can impact psychological health and vice versa. Classical pharmacotherapy of AR includes use of oral or topical antihistamines, oral antileukotrienes, topical corticosteroids, mast cell stabilizers, decongestants, and an anticholinergic agent. Among immunomodulatory treatments, immunotherapy is gaining widespread use, while antibody treatment is restricted mainly to resistant cases. Several small molecules with improved safety profile, or targeting novel mechanisms are in the clinical research. Newer antihistamines and corticosteroids with improved safety profile and antagonists of the prostaglandin D(2) (CRTH2) receptors are likely to be available for clinical use in the near future. Lack of properly validated animal models and complexities associated with clinical evaluation are some of the challenges facing the researchers in AR. Comprehensive understanding of immunological and neurological processes in AR would facilitate the future quest for more effective and safer management of this disease.

The effect of Helicobacter pylori on asthma and allergy

Current evidence indicates an inverse association between Helicobacter pylori and asthma and allergy. H. pylori is a Gram-negative bacterium which represents the major cause of peptic ulcer and gastric cancer, and preferentially elicits a T helper (Th)-1 response. Many H. pylori factors, such as the neutrophil-activating factor of H. pylori (HP-NAP), are able to drive Th-1 polarization and to display a powerful inhibition of allergic Th-2 response. This article proposes an overview of the actual knowledge about the effects of H. pylori on asthma and allergy. Special attention has been drawn to HP-NAP as a potential novel strategy for the prevention and treatment of asthma and atopy.

Seroepidemiology of Toxoplasma gondii infection in patients with vision and hearing impairments, cancer, HIV, or undergoing hemodialysis in Durango, Mexico

Toxoplasma gondii infection may cause a variety of symptoms involving virtually all organs. Little is known of the epidemiology of T. gondii infection in different patient groups in Mexico. We sought to determine the prevalence of T. gondii infection and associated epidemiological characteristics in 472 patients in Durango, Mexico. Participants were tested for T. gondii IgG and IgM antibodies. In addition, sociodemographic, clinical, and behavioral characteristics from each participant were obtained. Seroprevalences of T. gondii IgG antibodies were found in 7 (8.2%) of 85 patients with hearing impairment, 5 (10.0%) of 50 patients with hemodialysis, 28 (12.0%) of 234 patients with visual impairment, and 7 (6.8%) of 103 at risk of immunosuppression. In total, 47 (10%) of 472 subjects had IgG T. gondii antibodies; 6 (1.3%) of them also had IgM anti- T. gondii antibodies. Patients born in Durango State had a significantly lower prevalence of T. gondii infection than patients born in other Mexican states (9.0% vs. 21.4%, respectively; P < 0.05). Multivariate analysis showed that T. gondii infection was significantly associated with consumption of undercooked meat (adjusted odds ratio [OR] = 2.95; 95% confidence interval [CI]: 1.18-7.35) or raw cow's milk (adjusted OR = 2.52; 95% CI: 1.28-4.96), presence of cats at home (adjusted OR = 2.01; 95% CI: 1.06-3.78), raising animals (adjusted OR = 2.44; 95% CI: 1.06-5.63), or eating away from home (adjusted OR = 2.70; 95% CI: 1.03-7.11). In the group of patients with visual impairment, those with reflex impairment had a significantly higher frequency of T. gondii infection than those with normal reflexes (19% vs. 9.4%, respectively: P = 0.04). Results of the present study are the first step in the design of prevention programs to avoid the sequelae of toxoplasmosis.

Antibody and cytokine responses to house dust mite allergens and Toxoplasma gondii antigens in atopic and non-atopic Brazilian subjects

According to hygiene hypothesis, a lower exposure to infection is associated with increased prevalence of allergic diseases. This study aimed to investigate the association between atopy and Toxoplasma gondii (Tg) infection by analyzing the antibody and cytokine responses to house dust mite allergens and T. gondii antigens in Brazilian subjects. A total of 275 individuals were assessed and divided into atopics (n=129) and non-atopics (n=146) based on markers of allergy (positive skin prick test and ELISA-IgE to mite allergens) or Tg-seropositive (n=116) and Tg-seronegative (n=159) groups according to infection markers (positive ELISA-IgG to T. gondii). Tg-seropositive individuals presented lower allergenic sensitization (37%) to mite allergens than Tg-seronegative subjects (54%). A significant association was found between atopy and negative serology to T. gondii (OR: 2.0; 95% CI: 1.23-3.26; P<0.05). Proliferative responses and cytokine production after antigenic stimulation showed predominant synthesis of Th1-cytokines as IFN-gamma in Tg-seropositive patients, whether atopics or non-atopics. Conversely, Th2-cytokines as IL-5 prevailed in atopics compared to non-atopics, regardless the seropositivity to T. gondii. Levels of IL-10, IL-13, IL-17, and TGF-beta were not able to discriminate the groups. Hence, a negative association between atopy and infection by T. gondii was demonstrated for the first time in Brazilian subjects, focusing on the antibody and cytokine responses and indicating that the immunomodulation induced by the parasite may play a protective role in the development of allergic diseases.

Allergies: their role in cancer prevention

The nature of the biological relationships between cancers and allergies has intrigued researchers and health care providers for five decades. Three hypotheses have been proposed: antigenic stimulation predicts positive associations between cancers and allergies (i.e., allergy sufferers are more likely to get cancer), whereas immunosurveillance and prophylaxis predict inverse associations (i.e., allergy sufferers are less likely to get cancer). Immunosurveillance predicts inverse associations for cancers of all tissues and organ systems, and prophylaxis predicts inverse associations specifically for cancers of tissues and organ systems that interface with the external environment. To comparatively evaluate these hypotheses, we comprehensively reviewed the literature on cancer and allergies. We located 148 papers published from 1955 through 2006 that reported results of 463 studies of relationships between patients' histories of 11 specific allergies and cancers of 19 tissues and organ systems, and 183 studies of patients' histories of multiple allergies in relation to various types/sites of cancers. Analyses of these studies revealed that (1) frequencies of positive, inverse, and null allergy-cancer associations differed considerably among cancers of different tissues and organ systems; (2) more than twice as many studies reported inverse allergy-cancer associations as reported positive associations; (3) inverse associations were particularly common for cancers of the mouth and throat, brain glia, colon and rectum, pancreas, skin, and cervix but (4) particularly rare for cancers of the breast, prostate, and brain meninges, and for myeloma, non-Hodgkin's lymphoma, and myelocytic leukemia; (5) lung cancer was positively associated with asthma but inversely associated with other allergies; (6) inverse associations with allergies were more than twice as common for cancers of nine tissues and organ systems that interface with the external environment compared to cancers of nine tissues and organ systems that do not interface with the external environment; and (7) eczema, hives, and allergies to animal dander and food were most frequently inversely associated with cancers of tissues that interface with the external environment. Taken together, these results are more consistent with the prophylaxis hypothesis than the two alternatives. IgE is a widespread and ancient immunoglobulin isotype in mammals, occurring among all known marsupials, monotremes, and eutherians. The IgE system and its associated allergy symptoms may serve a common protective function: the rapid expulsion of pathogens, dangerous natural toxins, and other carcinogenic antigens before they can trigger malignant neoplasia in exposed tissues.

Allergen tolerance versus the allergic march: the hygiene hypothesis revisited

In addition to genetics, several environmental variables appear to impact allergic risk. Meta-analyses of epidemiologic studies presented in this article demonstrate a correlation between specific ambient exposures (eg, livestock, pets, endotoxin, and unpasteurized milk ingestion) and reduced allergic risk during childhood. Additional laboratory investigations discussed in this review characterized the intrinsic immunostimulatory activities of living environments. Considered together, results of these investigations suggest a novel paradigm by which early-life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic risk.

Specific IgE to allergens in cord blood is associated with maternal immunity to Toxoplasma gondii and rubella virus

BACKGROUND

Various studies have found reduced prevalences of atopic sensitization and atopic diseases in children previously exposed to infections or living conditions with a high microbial burden, such as the farming environment.

OBJECTIVE

We sought to determine the relationships of cord blood immunoglobulin E (IgE) with maternal health conditions before and during pregnancy.

METHODS

Pregnant women living in rural areas in five European countries were recruited in the third trimester of pregnancy. Information on maternal health during pregnancy was collected from maternity records and by questionnaires (n = 497). Specific IgE for inhalant and food allergens was assessed in cord blood and peripheral blood samples of the mothers.

RESULTS

Inverse associations of cord blood IgE to seasonal allergens with positive maternal records for Toxoplasma gondii (adjusted odds ratio = 0.37 [0.17-0.81]) and rubella virus (adjusted odds ratio = 0.35 [0.13-0.96]) were found. The previously described effect of prenatal farm exposure on IgE to seasonal allergens was partly confounded by a positive maternal record for T. gondii. The number of maternal siblings, maternal contact to cats during pregnancy or during her first year of life, predicted a positive maternal record for T. gondii.

CONCLUSIONS

Maternal immunity to T. gondii and rubella may impact on atopic sensitization in the fetus. A positive T. gondii record explained the previously identified effect of prenatal farm exposure on IgE to seasonal allergens only to a minor extent.

Endotoxin levels in cow's milk samples from farming and non-farming families - the PASTURE study

BACKGROUND

Children from farming families have less allergies than their peers. Consumption of farm milk or unpasteurized milk has been shown to explain (part of) the farming effect or protect against allergies independent of farming status.

OBJECTIVES

We investigated whether the protective effect of farm milk consumption can be explained by higher levels of bacterial endotoxin in milk.

METHODS

We measured endotoxin in approximately 400 farm milk and shop milk samples from farming and non-farming families, respectively, with the kinetic chromogenic Limulus Amebocyte Lysate test and compared endotoxin levels between groups defined by farming status and type of milk (farm milk/shop milk).

RESULTS

Endotoxin levels were significantly higher in milk samples from non-farming families compared to farming families [adjusted geometric means ratio (95% confidence interval)=2.61 (1.53-4.43)]. No significant difference in endotoxin levels was found between shop milk and farm milk samples [adjusted geometric means ratio (95% confidence interval)=1.56 (0.94-2.58)]. The difference between farming and non-farming families could be explained completely for farm milk and partially for shop milk by storage conditions and temperature during transportation to the fieldworker's home.

CONCLUSION

The farming effect and the effect of farm milk consumption cannot be explained by higher levels of endotoxin in milk from farmers and farm milk, respectively.

Living on a farm: impact on asthma induction and clinical course

Exposure to a farming environment protects individuals from respiratory allergy. The timing and duration of exposure seem to play critical roles. The largest reduction in risk of developing respiratory allergies is seen among those who are exposed prenatally and continuously thereafter. Contact with farm animals, at least in childhood, likely confers protection; other factors have not been completely identified. Also, the consumption of milk directly from the farm during childhood has been shown to be beneficial with respect to childhood asthma and allergies. Increased levels of microbial substances may contribute to the protective effects. The mechanisms by which such environmental exposures confer protection from respiratory allergies are not well understood. A number of gene-by-environment interactions have been observed with polymorphisms in genes of innate immunity receptors and exposure to farming environments. Increased levels of microbial exposures recognized by innate immune responses may affect adaptive immune responses resulting in decreased levels of atopic sensitization and asthma.

Childhood asthma epidemiology: insights from comparative studies of rural and urban populations

Asthma is one of the most common chronic respiratory disorders. Many epidemiology studies have suggested an increasing trend of asthma in many different regions of the world but the exact reasons explaining such trend remain unclear. Nevertheless, changing environmental factors are most likely important in explaining the trend of asthma. Studies in the past decade have clearly shown a mark difference in the prevalence between urban and rural regions. The consistent findings of a markedly lower prevalence of asthma in children and adults who have been brought up in a farming environment clearly indicate the importance of environmental influence of asthma development. Although the exact protective environmental factors in the rural region remain to be defined, there have been many studies suggesting that early exposure to microbes or microbial products may play a role in modulating the immune system so as to reduce the future risk of asthma and allergies. Advances in the understanding of the genetic predisposition and how these genetic factors may interact with specific environment factors are of paramount importance for the future development of primary preventive strategies for asthma.

A polymorphism in CD14 modifies the effect of farm milk consumption on allergic diseases and CD14 gene expression

BACKGROUND

Consumption of farm milk in early life is associated with less asthma and allergies.

OBJECTIVE

We hypothesized that genetic variation in the innate immunity receptor CD14 might modify the association between farm milk consumption and asthma and atopy.

METHODS

Questionnaire data, serum IgE levels, and genotypes for 4 single nucleotide polymorphisms in CD14 were assessed in farmers' and nonfarmers' children from 2 European populations (Allergy and Endotoxin study, n = 576; Prevention of Allergy Risk factors for Sensitization in children related to Farming and Anthroposophic Lifestyle study, n = 1539). In a subsample (n = 222) CD14 gene expression was measured in peripheral blood leukocytes. The effects of farm milk and CD14 genotypes on asthma, allergies, and CD14 expression and their interactions were investigated.

RESULTS

We found a significant interaction between genetic variation in CD14/-1721 and farm milk consumption. Adjusted odds ratios for the association between farm milk and asthma varied between the genotypes: AA, 0.18 (95% CI, 0.07-0.47); AG, 0.47 (95% CI, 0.26-0.86); and GG, 0.98 (95% CI, 0.46-2.08). Similar patterns were observed for symptoms of allergic rhinoconjunctivitis and pollen sensitization. CD14/-1721 also modified the association between farm milk and CD14 gene expression (adjusted geometric means ratios: AA, 1.61 (95% CI, 0.98-2.66); AG, 1.11 (95% CI, 0.71-1.72); and GG, 0.76 (95% CI, 0.39-1.48).

CONCLUSION

The protective effect of farm milk consumption on allergic diseases is stronger in children carrying the A allele in CD14/-1721 than in children homozygous for the G allele. This might be mediated through farm milk-induced upregulated CD14 gene expression.

CLINICAL IMPLICATIONS

Our results support the hypothesis that the inverse association between farm milk consumption and allergic diseases is mediated by CD14-activated innate immune mechanisms.

Inverse association of farm milk consumption with asthma and allergy in rural and suburban populations across Europe

BACKGROUND

Dietary interventions as a means for atopy prevention attract great interest. Some studies in rural environments claimed an inverse association between consumption of farm-produced dairy products and the prevalence of allergic diseases, but current evidence is controversial.

OBJECTIVE

To investigate whether consumption of farm-produced products is associated with a lower prevalence of asthma and allergy when compared with shop-purchased products.

METHODS

Cross sectional multi-centre study (PARSIFAL) including 14,893 children aged 5-13 years from five European countries (2823 from farm families and 4606 attending Steiner Schools as well as 5440 farm reference and 2024 Steiner reference children). A detailed questionnaire including a dietary component was completed and allergen-specific IgE was measured in serum.

RESULTS

Farm milk consumption ever in life showed a statistically significant inverse association with asthma: covariate adjusted odds ratio (aOR) 0.74 [95% confidence interval (CI) 0.61-0.88], rhinoconjunctivitis: aOR 0.56 (0.43-0.73) and sensitization to pollen and the food mix fx5 (cut-off level of >or=3.5 kU/L): aOR 0.67 (0.47-0.96) and aOR 0.42 (0.19-0.92), respectively, and sensitization to horse dander: aOR 0.50 (95% CI 0.28-0.87). The associations were observed in all four subpopulations and independent of farm-related co-exposures. Other farm-produced products were not independently related to any allergy-related health outcome.

CONCLUSION

Our results indicate that consumption of farm milk may offer protection against asthma and allergy. A deepened understanding of the relevant protective components of farm milk and a better insight into the biological mechanisms underlying this association are warranted as a basis for the development of a safe product for prevention.

Reduced risk of atopic sensitization among farmers: the Humboldt study

BACKGROUND

It needs to be clarified whether farming is associated with a reduced risk of atopy or allergic condition. There is a lack of consistent evidence for prevalences of atopy, respiratory allergy and asthma in adult farmers.

METHODS

A cross-sectional study of adults (n = 2,081) was conducted in the town of Humboldt, Sask. Allergy skin prick tests were conducted to determine atopic sensitization. Respiratory allergy and physician-diagnosed asthma were based on self-reporting. Logistic regression was used to assess the associations of atopy, respiratory allergy and asthma with farming practices, adjusting for other important variables.

RESULTS

Of 2,081 participants, 27.8% were farmers. Reduced risks of atopic sensitization, respiratory allergy and asthma were observed among farmers compared to non-farmers. After adjustment for sex and age, which are major confounders, the odds ratio for atopic sensitization was 0.79 (95% confidence interval: 0.65, 0.97) for farmers versus non-farmers. Asthma showed a similar trend; however, there was no statistically significant difference in either respiratory allergy or asthma rates observed between farmers and non-farmers.

CONCLUSIONS

The prevalence of atopy was lower in adult farmers than in non-farmers.

The effect of infectious burden on the prevalence of atopy and respiratory allergies in Iceland, Estonia, and Sweden

BACKGROUND

Epidemiologic reports on the effect of microbe exposure on the development of atopy and allergic asthma are inconsistent.

OBJECTIVES

The study investigates the association between serologic markers of infections and occurrence of atopy, allergic asthma, and rhinitis among adults in Iceland, Sweden, and Estonia.

METHODS

Individuals (n = 1249; mean age, 42 years) from Iceland, Sweden, and Estonia underwent a structured interview and blood sampling. Specific IgE was measured against 4 allergens, and IgG antibodies were measured against Helicobacter pylori, Toxoplasmosis gondii, hepatitis A virus, herpes simplex virus 1, Chlamydia pneumoniae, EBV, and cytomegalovirus.

RESULTS

Nonatopic subjects more often had positive serology for Helicobacter pylori, herpes simplex virus 1, Chlamydia pneumoniae, and cytomegalovirus. Having a low number (</=3) of IgG antibodies against the various infectious agents was an independent risk factor for atopy (odds ratio [OR], 1.43; 95% CI, 1.06-1.93), allergic asthma (OR, 1.82; 95% CI, 1.12-2.98), and allergic rhinitis (OR, 1.69; 95% CI, 1.21-2.37). The proportion of atopy that can be explained by a lower number (</=3) of infections was 6.7% in Iceland, 9.2% in Estonia, and 16.4% in Sweden, and 6.7%, 48.2%, and 33.4% for allergic asthma, respectively.

CONCLUSION

Our data are consistent with cumulative protective effect of infections against atopy and respiratory allergies irrespective of route of infection.

CLINICAL IMPLICATIONS

The study indicates what microbes or combination of microbes play a role in the complex interplay between hygiene and allergy and may contribute toward the understanding of the allergy epidemic.

Inverse association between rural environment in infancy and sensitization to rodents in adulthood

BACKGROUND

It is not known whether early childhood exposure to hygiene hypothesis factors modifies the risk of sensitization to aeroallergens among adults. Studying adults exposed to allergens in the workplace may help determine whether childhood exposures confer lasting protection against sensitization.

OBJECTIVE

To determine whether early life exposures influence the prevalence of sensitization to allergens in adulthood.

METHODS

Sensitization to rodents was determined by skin testing in a cross-sectional study among university employees with and without occupational exposure to laboratory animals. Demographic information was obtained by questionnaire.

RESULTS

Of 137 employees, 8% of workers without occupational exposure to laboratory animals and 24% of those with such exposure were sensitized to rodents (P = .007). None of 32 study participants who lived in a rural environment during their first year of life were rodent sensitized vs 18% of those who lived in other settings (P < .01). Rural setting in infancy was also associated with a decreased prevalence of sensitization to outdoor allergens (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.14-0.95). After adjusting for multiple confounders, sensitization to rodents remained rare among individuals who lived in a rural setting during infancy (OR, <0.15). Rodent sensitization was more prevalent among those with higher educational attainment (OR, 9.50; 95% CI, 1.10-82.02) and those sensitized to indoor allergens (OR, 6.22; 95% CI, 1.42-27.24). Sensitization to rodents was not significantly associated with having older siblings or sensitization to outdoor allergens.

CONCLUSIONS

Living in a rural setting during the first year of life is associated with protection from sensitization to rodent allergens in the workplace decades later.

Allergies, infections and the hygiene hypothesis--the epidemiological evidence

The 'hygiene hypothesis' was first proposed by Strachan in 1989 suggesting that infections and unhygienic contact with older siblings or through other exposures may confer protection from the development of allergic illnesses. This hypothesis has evolved in various ways exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and their effect on underlying responses of innate and adaptive immunity. So far a truly unifying concept is still lacking, but various pieces of a complex interplay between a host's immune response, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures become apparent. All these pieces eventually assemble to the clinical presentation of a complex syndrome namely of asthma and allergic illnesses. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future based on the concepts of the 'hygiene hypothesis'.