Felicia C. Madimenos

Life History, Immune Function, and Intestinal Helminths: Trade-Offs Among Immunoglobulin E, C-Reactive Protein, and Growth in an Amazonian Population

Objectives. Infection with helminths is associated with shifts in host immunity, including increased production of immunoglobulin E (IgE) and reduced inflammation. Given limited energy budgets, these shifts may involve changes in energy allocation toward competing demands. Here we test for potential trade‐offs between growth, IgE, and the inflammatory marker C‐reactive protein (CRP).

Analysis of variability of high sensitivity C-reactive protein in lowland Ecuador reveals no evidence of chronic low-grade inflammation.

C‐reactive protein (CRP) is a central component of innate immune defenses, and high sensitivity CRP has emerged as an important biomarker of chronic inflammation and cardiovascular disease risk. Prior analyses of CRP variability have reported stable between‐individual differences in CRP over time, but a limitation of current knowledge is that it is based on research conducted in post‐epidemiologic transition populations.

Evidence for a peak shift in a humoral response to helminths: age profiles of IgE in the Shuar of Ecuador, the Tsimane of Bolivia, and the U.S. NHANES.

Background The peak shift model predicts that the age-profile of a pathogens prevalence depends upon its transmission rate, peaking earlier in populations with higher transmission and declining as partial immunity is acquired. Helminth infections are associated with increased immunoglobulin E (IgE), which may convey partial immunity and influence the peak shift. Although studies have noted peak shifts in helminths, corresponding peak shifts in total IgE have not been investigated, nor has the age-patterning been carefully examined across populations. We test for differences in the age-patterning of IgE between two South American forager-horticulturalist populations and the United States: the Tsimane of Bolivia (n = 832), the Shuar of Ecuador (n = 289), and the U.S. NHANES (n = 8,336). We then examine the relationship between total IgE and helminth prevalences in the Tsimane. Methodology/Principal Findings Total IgE levels were assessed in serum and dried blood spots and age-patterns examined with non-linear regression models. Tsimane had the highest IgE (geometric mean  = 8,182 IU/ml), followed by Shuar (1,252 IU/ml), and NHANES (52 IU/ml). Consistent with predictions, higher population IgE was associated with steeper increases at early ages and earlier peaks: Tsimane IgE peaked at 7 years, Shuar at 10 years, and NHANES at 17 years. For Tsimane, the age-pattern was compared with fecal helminth prevalences. Overall, 57% had detectable eggs or larva, with hookworm (45.4%) and Ascaris lumbricoides (19.9%) the most prevalent. The peak in total IgE occurred around the peak in A. lumbricoides, which was associated with higher IgE in children <10, but with lower IgE in adolescents. Conclusions The age-patterning suggests a peak shift in total IgE similar to that seen in helminth infections, particularly A. lumbricoides. This age-patterning may have implications for understanding the effects of helminths on other health outcomes, such as allergy, growth, and response to childhood vaccination.

Implications of market integration for cardiovascular and metabolic health among an indigenous Amazonian Ecuadorian population

Background: Market integration (MI), the suite of social and cultural changes that occur with economic development, has been associated with negative health outcomes such as cardiovascular disease; however, key questions remain about how this transition manifests at the local level. Aim: The present paper investigates the effects of MI on health among Shuar, an indigenous lowland Ecuadorian population, with the goal of better understanding the mechanisms responsible for this health transition. Subjects and methods: This study examines associations between measures of MI and several dimensions of cardiovascular and metabolic health (fasting glucose, lipids [LDL, HDL and total cholesterol; triglycerides] and blood pressure) among 348 adults. Results: Overall, Shuar males and females have relatively favourable cardiovascular and metabolic health. Shuar who live closer to town have higher total (p < 0.001) and HDL cholesterol (p < 0.001), while Shuar in more remote regions have higher diastolic blood pressure (p = 0.007). HDL cholesterol is positively associated with consumption of market foods (r = 0.140; p = 0.045) and ownership of consumer products (r = 0.184; p = 0.029). Conclusions: This study provides evidence that MI among Shuar is not a uniformly negative process but instead produces complex cardiovascular and metabolic health outcomes.

Physical growth of the shuar: Height, Weight, and BMI references for an indigenous amazonian population

Information concerning physical growth among small‐scale populations remains limited, yet such data are critical to local health efforts and to foster basic understandings of human life history and variation in childhood development. Using a large dataset and robust modeling methods, this study aims to describe growth from birth to adulthood among the indigenous Shuar of Amazonian Ecuador.

Physical activity in an indigenous Ecuadorian forager-horticulturalist population as measured using accelerometry.

Minimal information on physical activity is available for non‐Western populations undergoing the transition to a market economy. This is unfortunate given the importance of these data for understanding health issues such as the global obesity epidemic. We consider the utility of using accelerometry technology to examine activity patterns and energy use regulation among indigenous Shuar, an Ecuadorian forager‐horticulturalist population undergoing economic and lifestyle change. We investigate sex differences in Shuar activity patterns and the effects of reproductive status on activity. Finally, we discuss the potential of accelerometry use in human biology research.

Low mineral density of a weight-bearing bone among adult women in a high fertility population.

Evolutionary theories of aging posit that greater reproductive effort causes somatic decline given a fundamental trade-off between investing energy in reproduction and repair. Few studies in high fertility human populations support this hypothesis, and problems of phenotypic correlation can obscure the expected trade-off between reproduction and somatic condition. This cross-sectional study investigates whether greater reproductive effort is associated with reduced calcaneal bone mineral density (BMD) among female Tsimane forager-farmers of lowland Bolivia. We also investigate whether female Tsimane BMD values are lower than sex- and age-matched US reference values, despite the fact that Tsimane engage in higher physical activity levels that can increase mechanical loading. To measure calcaneal BMD, quantitative ultrasonography was performed on 130 women (mean ± SD age = 36.6 ± 15.7, range = 15-75) that were recruited regardless of past or current reproductive status. Anthropometric and demographic data were collected during routine medical exams. As predicted, higher parity, short inter-birth interval, and earlier age at first birth are associated with reduced BMD among Tsimane women after adjusting for potential confounders. Population-level differences are apparent prior to the onset of reproduction, and age-related decline in BMD is greater among Tsimane compared with American women. Greater cumulative reproductive burden may lower calcaneal BMD individually and jointly with other lifestyle and heritable factors. Fitness impacts of kin transfers in adulthood may determine the value of investments in bone remodeling, and thus affect selection on age-profiles of bone mineral loss.

Soil-Transmitted Helminth Prevalence and Infection Intensity Among Geographically and Economically Distinct Shuar Communities in the Ecuadorian Amazon

Abstract: Soil-transmitted helminth (STH) infections can result in a variety of negative health outcomes (e.g., diarrhea, nutritional deficiencies). Market integration (MI; participation in market-based economies) has been suggested to alter levels of STH exposure due to associated changes in diet, sanitation, and behavior, but the effects are complicated and not well understood. Some effects of economic development result in decreased exposure to certain pathogens, and other factors can lead to higher pathogen exposure. With geographic location used as a proxy, the present study investigates the effects of economic development on parasite load among an indigenous population at multiple points along the spectrum of MI. This research has many implications for public health, including an increased understanding of how social and economic changes alter disease risk around the world and how changing parasite load affects other health outcomes (i.e., allergy, autoimmunity). Specifically, this study examines the prevalence of intestinal helminths among the Shuar, an indigenous group in the Morona-Santiago region of Ecuador, from 2 geographically/economically separated areas, with the following objectives: (1) report STH infection prevalence and intensity among Shuar; (2) explore STH infection prevalence and intensity as it relates to age distribution in the Shuar population; (3) compare STH infection patterns in geographically and economically separated Shuar communities at different levels of MI. Kato-Katz thick smears were made from fresh stool samples and examined to determine STH presence/intensity. Results indicate that 65% of the 211 participants were infected with at least 1 STH. Twenty-five percent of the sample had coinfections with at least 2 species of helminth. Infection was more common among juveniles (<15 yr) than adults. Infection prevalence and intensity was highest among more isolated communities with less market access. This study documents preliminary associations between STH infection and exposure to MI, with implications for public health research and interventions.

Heterogeneous effects of market integration on sub-adult body size and nutritional status among the Shuar of Amazonian Ecuador

Abstract Background: Market integration (MI)—increasing production for and consumption from a market-based economy—is drastically altering traditional ways of life and environmental conditions among indigenous Amazonian peoples. The effects of MI on the biology and health of Amazonian children and adolescents, however, remain unclear. Aim: This study examines the impact of MI on sub-adult body size and nutritional status at the population, regional and household levels among the Shuar of Amazonian Ecuador. Subjects and methods: Anthropometric data were collected between 2005–2014 from 2164 Shuar (aged 2–19 years) living in two geographic regions differing in general degree of MI. High-resolution household economic, lifestyle and dietary data were collected from a sub-sample of 631 participants. Analyses were performed to investigate relationships between body size and year of data collection, region and specific aspects of household MI. Results: Results from temporal and regional analyses suggest that MI has a significant and overall positive impact on Shuar body size and nutritional status. However, household-level results exhibit nuanced and heterogeneous specific effects of MI underlying these overarching relationships. Conclusion: This study provides novel insight into the complex socio-ecological pathways linking MI, physical growth and health among the Shuar and other indigenous Amazonian populations.

Reproductive effects on skeletal health in Shuar women of Amazonian Ecuador: A life history perspective†

Clinical and epidemiological research suggest that bone mineral density (BMD) in women is shaped by various reproductive factors such as parity and lactation patterns. However, the extent of these effects on BMD remains unclear because of contradictory findings and a focus on industrialized populations. Because fertility patterns in these groups are vastly different than those of women from non‐Western, subsistence populations, our current understanding of the reproductive effects on skeletal health is incomplete. Using a life history perspective, this study examines the relationship between reproductive factors and bone density among women from the Indigenous Shuar population, an Amazonian Ecuadorian forager‐horticulturalist group.