Longitudinal study of tuberculosis outcomes among immunologically naive Aché natives of Paraguay

Orangutan males make increased use of social learning opportunities, when resource availability is high

Humans' colonization of diverse habitats relied on our ancestors' abilities to innovate and share innovations with others. While ecological impacts on innovations are well studied, their effect on social learning remains poorly understood. We examined how food availability affects social learning in migrant orangutan unflanged males, who may learn from local orangutans through peering (i.e., observational social learning). We analyzed 1,384 dyadic associations, including 360 peering events, among 46 wild Sumatran orangutan and 25 Bornean orangutan males, collected over 18 years. Migrants' peering rates significantly increased with higher food availability and time spent in proximity to others. Furthermore, migrants in the more sociable Sumatran population exhibited significantly higher peering rates compared to the Borneans, suggesting intrinsic and/or developmental effects of food availability on social learning. These findings emphasize the importance of investigating ecological effects on social learning on the immediate, developmental, and intrinsic levels for our understanding of cultural evolution.

Pandemics, past and present: The role of biological anthropology in interdisciplinary pandemic studies

Biological anthropologists are ideally suited for the study of pandemics given their strengths in human biology, health, culture, and behavior, yet pandemics have historically not been a major focus of research. The COVID‐19 pandemic has reinforced the need to understand pandemic causes and unequal consequences at multiple levels. Insights from past pandemics can strengthen the knowledge base and inform the study of current and future pandemics through an anthropological lens. In this paper, we discuss the distinctive social and epidemiological features of pandemics, as well as the ways in which biological anthropologists have previously studied infectious diseases, epidemics, and pandemics. We then review interdisciplinary research on three pandemics–1918 influenza, 2009 influenza, and COVID‐19–focusing on persistent social inequalities in morbidity and mortality related to sex and gender; race, ethnicity, and Indigeneity; and pre‐existing health and disability. Following this review of the current state of pandemic research on these topics, we conclude with a discussion of ways biological anthropologists can contribute to this field moving forward. Biological anthropologists can add rich historical and cross‐cultural depth to the study of pandemics, provide insights into the biosocial complexities of pandemics using the theory of syndemics, investigate the social and health impacts of stress and stigma, and address important methodological and ethical issues. As COVID‐19 is unlikely to be the last global pandemic, stronger involvement of biological anthropology in pandemic studies and public health policy and research is vital.

Tuberculosis incidence inequalities and its social determinants in Manaus from 2007 to 2016

Background

Brazil is among the 30 countries with high-burden of tuberculosis worldwide, and Manaus is the capital with the highest tuberculosis incidence. The accelerated economic and population growth in Manaus in the last 30 years has strengthened the process of social stratification that may result in population groups that are less favored in terms of healthcare and are vulnerable to infection and illness due to tuberculosis. This study aimed to characterize inequalities associated with tuberculosis incidence in relation to the socioeconomic and demographic characteristics of the resident population of Manaus and to identify their determinants from 2007 to 2016.

Methods

An ecological study was conducted using the data from the Diseases Notification Information System. Tuberculosis incidence rates by population characteristics (gender, ethnicity, and socioeconomic level) were calculated for each year, studied, and represented in equiplot charts. To measure the disparity of tuberculosis incidence in the resident population in Manaus, the Gini index of tuberculosis in each neighborhood was calculated based on the incidence rates of the census sectors. A thematic map was constructed to represent the spatial distribution of tuberculosis incidence inequality. Linear regression models were used to identify the relationship between the tuberculosis incidence inequality and its social determinants.

Results

From 2007 to 2016, there was an increase in the tuberculosis incidence in Manaus, together with an increase in incident inequality among genders, ethnic groups, and socioeconomic level. The incidence of tuberculosis inequality was associated with the inequalities of its possible determinants (Gini of the proportion of male population, Gini of the proportion of indigenous population, Gini of the proportion of illiteracy, Gini of income, Gini of the proportion of households connected to the water network, and Gini of the mean number of bathrooms per inhabitant), the per capita income, and the proportion of cases with laboratory confirmation.

Conclusions

Disparities in tuberculosis incidence in the resident population in neighborhoods can be explained by the sociodemographic and economic heterogeneity. Our findings recommend that public policies and tuberculosis control strategies consider differences in the determinants of tuberculosis inequality for the development of specific actions for each population group.

Genetic Resistance to Mycobacterium tuberculosis Infection and Disease

Natural history studies of tuberculosis (TB) have revealed a spectrum of clinical outcomes after exposure to Mycobacterium tuberculosis, the cause of TB. Not all individuals exposed to the bacterium will become diseased and depending on the infection pressure, many will remain infection-free. Intriguingly, complete resistance to infection is observed in some individuals (termed resisters) after intense, continuing M. tuberculosis exposure. After successful infection, the majority of individuals will develop latent TB infection (LTBI). This infection state is currently (and perhaps imperfectly) defined by the presence of a positive tuberculin skin test (TST) and/or interferon gamma release assay (IGRA), but no detectable clinical disease symptoms. The majority of healthy individuals with LTBI are resistant to clinical TB, indicating that infection is remarkably well-contained in these non-progressors. The remaining 5-15% of LTBI positive individuals will progress to active TB. Epidemiological investigations have indicated that the host genetic component contributes to these infection and disease phenotypes, influencing both susceptibility and resistance. Elucidating these genetic correlates is therefore a priority as it may translate to new interventions to prevent, diagnose or treat TB. The most successful approaches in resistance/susceptibility investigation have focused on specific infection and disease phenotypes and the resister phenotype may hold the key to the discovery of actionable genetic variants in TB infection and disease. This review will not only discuss lessons from epidemiological studies, but will also focus on the contribution of epidemiology and functional genetics to human genetic resistance to M. tuberculosis infection and disease.

Hunter-gatherer diets and human behavioral evolution

Human behavior and physiology evolved under conditions vastly different from those which most humans inhabit today. This paper summarizes long-term dietary studies conducted on contemporary hunter-gatherer populations (sometimes referred to as foragers). Selected studies for the most part that use evolutionary theoretical perspectives and data collection methods derived from the academic field of human behavioral ecology, which derives relatively recently from the fields of evolutionary biology, ethology, population biology and ecological anthropology. I demonstrate how this body of research illuminates ancestral patterns of food production, consumption and sharing, infant feeding, and juvenile subsistence contributions in hunter-gatherer economies. Insights from hunter-gatherer studies are then briefly discussed within the context of better-studied human populations that are Westernized, Educated, Industrialized, Rich, and Democratic (WEIRD).

The role of variants from the innate immune system genes in tuberculosis and skin test response in a Native American population

Native American populations show higher tuberculosis (TB) mortality and infectivity rates than non-Native populations. Variants in the innate immune system seem to have an important role on TB susceptibility. The role of some innate immune system variants in TB susceptibility and/or skin test response (PPD) were investigated in the Aché, a Native American population. Complement receptor 1 and toll like receptor 9 variants were associated with anergy to PPD and protection to TB, respectively. These findings demonstrate an important role of the innate immune system variants in TB susceptibility.

Variability of innate immune system genes in Native American populations-relationship with history and epidemiology

OBJECTIVES

The immune system of a host, defending him/her against invading pathogens, has two main subsystems: innate immunity and acquired immunity. There are several evidences showing that Native American populations are immunologically different from non-Native populations. Our aim was to describe the variability of innate immune system genes in Native American populations.

MATERIALS AND METHODS

We investigated heterozygozities and patterns of population differentiation (FST ) of 14 polymorphisms related to the innate immune response in five Native American populations (Aché, Guarani-Kaiowá, Guarani-Ñandeva, Kaingang, and Xavante) and the results were compared with the three major world population data (YRI, CEU, and CHB) available at the 1,000 genomes database.

RESULTS

Mean heterozygosities ranged between 0.241 ± 0.057 (Aché) and 0.343 ± 0.033 (Kaingang), but no significant differences were observed (Friedman test, P = 0.197). Mean heterozygosities were also not significantly different when Amerindians were pooled and compared with the 1000 genomes populations (Friedman test, P = 0.506). When the Native American populations were grouped as Amerindians, a significantly higher FST value (0.194) was observed between the Amerindian and African populations. The Ewens-Watterson neutrality test showed that these markers are not under strong selective pressure.

DISCUSSION

Native American populations present similar levels of heterozygosity as those of other continents, but are different from Africans in the frequency of polymorphisms of innate immune genes. This higher differentiation is probably due to demographic processes that occurred during the out-of-Africa event.

Health of Indigenous Peoples

Indigenous populations worldwide are experiencing social, cultural, demographic, nutritional, and psychoemotional changes that have a profound impact on health. Regardless of their geographical location or sociopolitical situation, health indicators are always poorer for indigenous populations than for nonindigenous ones. The determinants of this gap are multiple and interactive, and their analysis requires a biocultural framework. Indigenous populations suffer from lower life expectancy, high infant and child mortality, high maternal morbidity and mortality, heavy infectious disease loads, malnutrition, stunted growth, increasing levels of cardiovascular and other chronic diseases, substance abuse, and depression. The devastating effects of colonization, the loss of ancestral land, and language and cultural barriers for access to health care are among the most salient themes characterizing the poor health situation of indigenous people. Anthropology is extremely well suited to address the interplay among social, economic, and political forces that shape the local experiences of illness.

Modeling the potential impact of host population survival on the evolution of M. tuberculosis latency

Tuberculosis (TB) is an infectious disease with a peculiar feature: Upon infection with the causative agent, Mycobacterium Tuberculosis (MTB), most hosts enter a latent state during which no transmission of MTB to new hosts occurs. Only a fraction of latently infected hosts develop TB disease and can potentially infect new hosts. At first glance, this seems like a waste of transmission potential and therefore an evolutionary suboptimal strategy for MTB. It might be that the human immune response keeps MTB in check in most hosts, thereby preventing it from achieving its evolutionary optimum. Another possible explanation is that long latency and progression to disease in only a fraction of hosts are evolutionary beneficial to MTB by allowing it to persist better in small host populations. Given that MTB has co-evolved with human hosts for millenia or longer, it likely encountered small host populations for a large share of its evolutionary history and had to evolve strategies of persistence. Here, we use a mathematical model to show that indeed, MTB persistence is optimal for an intermediate duration of latency and level of activation. The predicted optimal level of activation is above the observed value, suggesting that human co-evolution has lead to host immunity, which keeps MTB below its evolutionary optimum.

Burden of tuberculosis in indigenous peoples globally: a systematic review

BACKGROUND

The burden of tuberculosis (TB) in the estimated 370 million indigenous peoples worldwide is unknown.

OBJECTIVE

To conduct a literature review to summarize the TB burden in indigenous peoples, identify gaps in current knowledge, and provide the foundation for a research agenda prioritizing indigenous health within TB control.

METHODS

A systematic literature review identified articles published between January 1990 and November 2011 quantifying TB disease burden in indigenous populations worldwide.

RESULTS

Among the 91 articles from 19 countries included in the review, only 56 were from outside Australia, Canada, New Zealand and the United States. The majority of the studies showed higher TB rates among indigenous groups than non-indigenous groups. Studies from the Amazon generally reported the highest TB prevalence and incidence, but select populations from South-East Asia and Africa were found to have similarly high rates of TB. In North America, the Inuit had the highest reported TB incidence (156/100000), whereas the Metis of Canada and American Indians/Alaska Natives experienced rates of <10/100000. New Zealand's Maori and Pacific Islanders had higher TB incidence rates than Australian Aborigines, but all were at greater risk of developing TB than non-indigenous groups.

CONCLUSION

Where data exist, indigenous peoples were generally found to have higher rates of TB disease than non-indigenous peoples; however, this burden varied greatly. The paucity of published information on TB burden among indigenous peoples highlights the need to implement and improve TB surveillance to better measure and understand global disparities in TB rates.

The identification and restitution of human remains from an Aché girl named "Damiana": an interdisciplinary approach

In June 2010, the postcranial skeleton of an adolescent girl was returned by the Natural History Museum of La Plata, Argentina, to the Aché community in Paraguay. In March 2011 the missing skull was identified in the anatomical collection of Charité in Berlin. We initiated a historical and anthropological investigation to confirm the identity of the human remains and to reconstruct the fate of the individual in question in its historical context. Anthropological publications from Argentina had indicated that the girl named "Damiana" was abducted by colonising settlers in Southern Paraguay in 1897 at the age of 3-4 years, later taken to La Plata in Argentina where she grew up as a "maidservant", and died in 1907 of "galloping consumption". In accordance with these reports, the present palaeopathological investigation confirms tuberculous meningitis as a likely cause of death. It also demonstrates some markers of "stress", the nature of which, however, is difficult to determine. Surviving letters and publications by Berlin anatomist Hans Virchow reveal that the girl's preserved head was sent from La Plata to Berlin in January 1908 for comparative investigations in the context of the racial theories of the time. We were convinced that the justified wishes of the Aché community to bury these remains alongside those restituted in 2010 outweighed any future scientific interest in these remains. In April 2012, the skull and two related specimens were returned from the Charité to the Aché community, mediated by the Paraguayan ambassador in Berlin.

Genetic polymorphism and immune response to tuberculosis in indigenous populations: a brief review

We systematically reviewed studies of the immune response to tuberculosis and the genetic polymorphisms associated with Th1- or Th2-mediated cytokine expression in indigenous populations. A bibliographic search was performed on the Medline and ISI databases and included studies published between January 1980 and October 2011. The search terms were tuberculosis, American Indians, Amerindian, indigenous, Indians, native people, aboriginal, immun*, host immune, immune response, cytokine*, polymorphism*, and gene. Regardless of their design, studies that evaluated immunoglobulin, cytokine levels and genetic polymorphisms that altered cytokine expression were included. Thirteen studies met the inclusion criteria. The majority of studies were performed in Latin America, and five investigated the Warao ethnic group of Venezuela. Most of the investigations indirectly evaluated the immune response. Higher anergy to the tuberculin skin test, higher IgG4 and IgM levels, higher IL-5 production and lower TNF-α, IL-12p40 and IFN-γ production were found in the indigenous populations. The studies also reported a predominantly Th2-type response in these populations and a possibly higher susceptibility to tuberculosis. A better understanding of the relevant genetic polymorphisms and their role in immune regulation would help to clarify the immunogenetic mechanisms of TB infection in these populations. This information would be useful for identifying new treatments and preventing infection and progression to active disease.

Tuberculosis and leprosy in perspective

Two of humankind's most socially and psychologically devastating diseases, tuberculosis and leprosy, have been the subject of intensive paleopathological research due to their antiquity, a presumed association with human settlement and subsistence patterns, and their propensity to leave characteristic lesions on skeletal and mummified remains. Despite a long history of medical research and the development of effective chemotherapy, these diseases remain global health threats even in the 21st century, and as such, their causative agents Mycobacterium tuberculosis and M. leprae, respectively, have recently been the subject of molecular genetics research. The new genome-level data for several mycobacterial species have informed extensive phylogenetic analyses that call into question previously accepted theories concerning the origins and antiquity of these diseases. Of special note is the fact that all new models are in broad agreement that human TB predated that in other animals, including cattle and other domesticates, and that this disease originated at least 35,000 years ago and probably closer to 2.6 million years ago. In this work, we review current phylogenetic and biogeographic models derived from molecular biology and explore their implications for the global development of TB and leprosy, past and present. In so doing, we also briefly review the skeletal evidence for TB and leprosy, explore the current status of these pathogens, critically consider current methods for identifying ancient mycobacterial DNA, and evaluate coevolutionary models.

Cytokine genes are associated with tuberculin skin test response in a native Brazilian population

Tuberculosis was a major cause of population decline among Brazilian indigenous peoples and remains a leading cause of morbidity and mortality among them. Despite high BCG coverage, results of Tuberculin Skin Test (TST) reactivity have shown high rates of anergy in Amazonian Indians. Given the high prevalence of anergy in these populations and the fact that genetic host factors play an important role in susceptibility to Mycobacterium tuberculosis (MTB), the aim of this study was to evaluate the association of nineteen polymorphisms in fifteen genes related to immune response and anergy in the Xavante, an indigenous group from Brazil. A total of 481 individuals were investigated. TST anergy was observed in 69% of them. Polymorphisms in four genes showed absence or very low variability: SP110, PTPN22, IL12RB1 and IL6. IFNG +874 A/T heterozygotes and IL4-590 C/C homozygotes were more frequent in those individuals who presented a positive TST (prevalence ratios of 1.9 and 2.0 respectively). The risk of anergy was 1.5 in IL10-1082 G/G homozygotes when compared to carriers for the A allele. In indigenous groups such as the Xavante exposure to a variety of infections, associated with specific genetic factors, may disturb the T-helper 1 and T-helper 2 balance leading to increased immunological susceptibility.

Diet, tuberculosis, and the paleopathological record

Osseous manifestation of infectious disease is of paramount importance to paleopathologists seeking to interpret ancient health, but the relationships among infectious agent exposure, development of disease, and skeletal involvement are complex. The outcome of an exposure strongly depends on multiple factors, including ecology, diet, nutrition, immune function, and the genetics of pathogen and host. Mycobacterial diseases are often studied in ancient remains but also are especially influenced by these factors; individual and population differences in severity and course are apparent following onset of active disease. The osteological record for these diseases represents the complex interplay of host and pathogen characteristics influencing within- and among-individual skeletal lesion prevalence and distribution. However, many of these characteristics may be assessed independently through the archaeological record. Here, we explore the contributions of dietary protein and iron to immune function, particularly the course and outcome of infection with Mycobacterium tuberculosis. We emphasize how nutrition may influence the dissemination of bacilli to the skeleton and subsequent formation of diagnostic lesions. We then generate models and hypotheses informed by this interplay and apply them to four prehistoric New World areas. Finally, discrepancies between our expectations and the observed record are explored as a basis for new hypotheses.

Life history theory and the immune system: steps toward a human ecological immunology

Within anthropology and human biology, there is growing interest in immune function and its importance to the ecology of human health and development. Biomedical research currently dominates our understanding of immunology, and this paper seeks to highlight the potential contribution of a population-based, ecological approach to the study of human immune function. Concepts from life-history theory are applied to highlight the major challenges and demands that are likely to shape immune function in a range of ecological contexts. Immune function is a major component of maintenance effort, and since resources are limited, trade-offs are expected between investment in maintenance and other critical life-history functions involving growth and reproduction. An adaptationist, life-history perspective helps make sense of the unusual developmental trajectory of immune tissues, and emphasizes that this complex system is designed to incorporate information from the surrounding ecology to guide its development. As a result, there is substantial population variation in immune development and function that is not considered by current biomedical approaches. In an attempt to construct a framework for understanding this variation, immune development is considered in relation to the competing life-history demands that define gestation, infancy, childhood, adolescence, and adulthood. Each life stage poses a unique set of adaptive challenges, and a series of hypotheses is proposed regarding their implications for immune development and function. Research in human ecological immunology is in its earliest stages, but this is a promising area of exploration, and one in which anthropology is well-positioned to make important contributions.

Vitamin D receptor gene polymorphisms and susceptibility M. tuberculosis in Native Paraguayans

Tuberculosis (TB) is a significant health problem for most of the world's populations, and prevalence among indigenous groups is typically higher than among their nonindigenous neighbors. Native South Americans experience high rates of TB, but while research in several other world populations indicates that susceptibility is multifactorial, polygenic, and population-specific, little work has been undertaken to investigate factors involved in Native American susceptibility. We conducted a family-based association study to examine immunologically relevant polymorphisms of a candidate gene, the vitamin D receptor, in conjunction with three measures of TB status in two Native Paraguayan populations, the Aché and the Avá. This is the first large-scale genetic analysis of Native South Americans to examine susceptibility to both infection and disease following exposure to M. tuberculosis. These two types of susceptibility reflect differences in innate and acquired immunity that have proven difficult to elucidate in other populations. Our results indicate that among the Aché, the FokI F allele protects individuals from infection, while the TaqI t allele protects against active disease but not infection. In particular, FF homozygotes are 17 times more likely to test positive for exposure to TB, but no more likely to have ever been diagnosed with active TB. TT individuals are 42 times less likely to mount a delayed-type hypersensitivity response, and the T allele was significantly more likely to have been transmitted to offspring who have been diagnosed with active TB. This ongoing research is of vital importance to indigenous groups of the Americas, because if there is a population-specific component to TB susceptibility, it will likely prove most effective to incorporate this into future treatment and prevention strategies.

Population variation and differences in serum leptin independent of adiposity: a comparison of Ache Amerindian men of Paraguay and lean American male distance runners

Background

Serum leptin variation is commonly associated with fat percentage (%), body mass index (BMI), and activity. In this investigation, we report population differences in mean leptin levels in healthy men as well as associations with fat % and BMI that are independent of these factors and reflect likely variation resulting from chronic environmental conditions.

Methods

Serum leptin levels, fat %, and BMI were compared between lean American distance runners and healthy Ache Native Americans of Paraguay. Mean levels were compared as were the regressions between fat %, BMI, and leptin. Comparisons were performed between male American distance runners (n = 13, mean age 32.2 ± 9.2 SD) and highly active male New World indigenous population (Ache of Paraguay, n = 20, mean age 32.8 ± 9.2) in order to determine whether significant population variation in leptin is evident in physically active populations living under different ecological circumstances independent of adiposity and BMI.

Results

While the Ache were hypothesized to exhibit higher leptin due to significantly greater adiposity (fat %, Ache 17.9 ± 1.8 SD; runners 9.7 ± 3.2, p < 0.0001), leptin levels were nonetheless significantly higher in American runners (Ache 1.13 ng/ml ± 0.38 SD; runners 2.19 ± 1.15; p < 0.007). Significant differences in the association between leptin and fat % was also evident between Ache and runner men. Although fat % was significantly related with leptin in runners (r = 0.90, p < 0.0001) fat % was negatively related in Ache men (r = -0.50, p < 0.03).

Conclusion

These results illustrate that chronic ecological conditions in addition to activity are likely factors that contribute to population variation in leptin levels and physiology. Population variation independent of adiposity should be considered to be an important source of variation, especially in light of ethnic and population differences in the incidence and etiology of obesity, diabetes, and other metabolic conditions.

Survey for tuberculosis in an indigenous population of Amazonia: the Suruí of Rondônia, Brazil

A cross-sectional survey was carried out in 2003 to investigate the epidemiology of tuberculosis (TB) among the Suruí Indians, Brazilian Amazon. A total of 736 subjects (50.7% females) were examined (80% of the total population). TB suspects underwent standardised evaluation for the presence of signs and/or symptoms of active TB, including chest radiography, PPD skin test, sputum microscopy examination for acid-fast bacilli and mycobacterial culture. A Bacillus Calmette-Guerin vaccine scar was detected in 699 individuals (95.0%). Of all the individuals examined, 120 (16.3%) had undergone previous TB treatment (46.7% females). One hundred and nine individuals were assessed as TB suspects (52.3% females). The survey identified six new cases of TB in the Suruí (three men and three women). Five of the six cases came from only two of the ten villages. Mycobacterium tuberculosis colonies grew from 5 (4.6%) samples (only two of which were also smear-positive) and mycobacteria other than M. tuberculosis were isolated from 14 (12.8%) samples. Diagnosis of TB based exclusively on clinical grounds was established only in the case of a 4-year-old girl. Based on this survey, the prevalence of active TB in the sampled group (N=736) was 815.2 per 100000. This study highlights the urgent need to review and strengthen control strategies directed at indigenous peoples in the country, taking into consideration their social, cultural and environmental differences.

Teste tuberculínico na estimativa da prevalência de infecção por Mycobacterium tuberculosis em populações indígenas do continente americano: uma revisão da literatura

Realizou-se revisão sistemática da literatura sobre trabalhos que utilizaram PPD para estimar a prevalência e o risco de infecção tuberculosa entre os povos indígenas do continente americano. Foram consultadas as bases de dados MEDLINE e LILACS, utilizando-se a combinação dos seguintes descritores: "tuberculosis", "south american indians", "north american indians", "tuberculin skin test", "PPD", "risk assessment" e "BCG vaccine", para o período de 1974/2004. Foram incluídos estudos longitudinais e seccionais que consideraram como desfecho a prevalência de infecção por M. tuberculosis definida por reações > 5mm e > 10mm. Foi possível localizar 54 artigos, dos quais 16 foram incluídos nesta revisão. Com base nos artigos selecionados, foram contabilizadas 13.186 pessoas, sendo 50% menores de 15 anos. A prevalência oscilou de 0 a 93,4% e o risco de infecção de 0 a 35,4%. A análise da heterogeneidade nas condições ambientais e nos métodos utilizados para estimar a infecção entre os estudos revisados demonstrou que o teste tuberculínico foi oportuno em decisões clínicas (p.ex., início da quimioprofilaxia), e que os inquéritos tuberculínicos são úteis para avaliar as medidas de controle da tuberculose entre os povos indígenas.

HUMAN RIGHTS, BIOMEDICAL SCIENCE, AND INFECTIOUS DISEASES AMONG SOUTH AMERICAN INDIGENOUS GROUPS

Despite the efforts of international health agencies to reduce global health inequalities, indigenous populations around the world remain largely unaffected by such initiatives. This chapter reviews the biomedical literature indexed by the PubMed database published between 1963 and 2003 on South American indigenous populations, a total of 1864 studies that include 63,563 study participants. Some language family groupings are better represented than are others, and lowland groups are better represented than are highland groups. Very few studies focus on major health threats (e.g., tuberculosis, influenza), public health interventions, or mestizo-indigenous epidemiological comparisons. The prevalence rates of three frequently studied infections—parasitism, human T-cell lymphotropic viral infection (HTLV), and hepatitis—are extraordinarily high, but these facts have been overlooked by national and international health agencies. This review underscores the urgent need for interventions based on known disease prevalence rates to reduce the burden of infectious diseases in indigenous communities.

Differential cytokine genotype frequencies among Canadian Aboriginal and Caucasian populations

Genetic diversity related to the human immune response is a key factor in individual and population survival throughout human history. Population diversity in disease susceptibility and resistance have been identified and linked to differences in cytokine mRNA and protein expression levels. Polymorphisms in the regulatory regions of cytokine genes can influence gene transcription levels and they have been associated with susceptibility to, and/or severity of, autoimmune disorders such as rheumatoid arthritis, meningococcus and sepsis. It is reported here that in two study populations, Canadian Aboriginal individuals have a higher frequency of cytokine single-nucleotide polymorphisms favouring a low production of TNFalpha, IFNgamma and IL-10 and high production of IL-6 as compared to a Caucasian population. We postulate that the evolution of this unique cytokine genotype profile may be linked to the Aboriginal adaptation to selection pressures related to an environment in which helminthic, parasitic and fungal infections predominated.