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The epidemiology of infectious diseases among South American Indians
As we speak, many Yanomamo and other South American Indians are ill and dying from preventable diseases. At the same time, many other indigenous groups await contact with outsiders, and when it finally occurs, a huge fraction of them will die, again, from preventable causes. Why is this epidemiological profile so bleak at a time when the causative organisms of this suffering are well known, and when effective drugs and vaccines are available to prevent it? What forces continue to deprive South American Indians of the scientific knowledge and technology that protects many other people from pathogens including everyone in this audience? I suggest that these forces are complex, that to understand them and influence their course we need to do more, rather than less research, and that the anti-science views that Patrick Tierney promotes in his new book have the potential to unjustly deny indigenous people of South America the right to combat health problems through scientific research and interventions.
Tierney’s book promotes anti-science views by falsely accusing scientists of unethical experimentation among the Yanomamo. His charges have been refuted by National Academy of Science specialists and the University of Michigan in widely distributed documents, and I will not discuss them here. Instead I will focus on how Tierney’s book promotes anti-science views by giving the false impression that the causes of poor health status of the Yanomamo and other indigenous people are simple and easy to identify by anyone without carefully designed epidemiological and medical research. Tierney suggests that only treatment but not research is justifiable with indian populations. To the contrary, I will argue that in order to intervene effectively, and in ways that truly benefit South American Indians, a great deal of research needs to be done on relationships between social inequities and the uniqueness of the indigenous immune response to infectious diseases. Indeed, the book that needs to be written in order to help the Yanomamo and other Amerindians should be entitled Darkness in El Dorado: how governments, international agencies and scientists can help reverse the devastation of the Amazon.
Scientists can help by identifying the social causes of such devastation and by collaborating with international teams in efforts to counter their effects. One of the most important and well-known causes of indigenous suffering is governmental unresponsiveness to land rights violations and the increasingly precarious health status of native populations. Throughout South America, local governments allocate meager and inadequate resources to indigenous help programs and only a fraction of these resources is ever seen by native communities due to rampant corruption and embezzlement. Furthermore, laws that protect indigenous rights are infrequently implemented. For example, in 1986, I reported to the Direcccion de Asuntos Indigenas of Venezuela that only 1 indigenous land title was legitimate out of 152 that had been initially decreed by President Rafael Caldera in 1972. Several months later, Peruvian government officials threatened to expel my husband and I from our field site because we had treated the sick during a massive respiratory epidemic in a remote Machiguenga village. In 1991 several of our Hiwi Indian collaborators were murdered without cause by Venezuelan nationals. All these events were reported to government officials with no response. They were ignored along with many other instances of wrongdoing observed by us and countless other anthropologists. Darkness in El Dorado did not come from actions of a geneticist, a sociobiologist and a filmmaker in one tiny corner of the Amazon. It has been produced through hundred of years of racist colonialism and neglect. The devastation of the Amazon will only stop when governments and international agencies respond to human rights violations in an effective manner with the help of scientists.
Scientists in fact have a special role in this process–they can also help by isolating biological causes of poor health status. Biological anthropologists have repeatedly shown that South American Indians are highly susceptible to diseases of contact. In fact, the mortality rate of Amerindians at contact due to the exposure to measles is more than a hundredfold higher than in other populations even when medical help is provided to them. Much less attention has been given to the susceptibility that lingers on for many generations after contact. Recent large surveys of rural populations of South America show that natives invariably suffer from worse health than do their neighbors of European and African descent. Biological influences may account for these poor outcomes during and after contact. Inefficient immune response due to high genetic homozygosity and extensive macroparasitic infection are potentially two of the more important contributors. Unlike other populations, South American natives have much less heterogeneity in loci that control the immune system, and this low heterogeneity increases the risk of many infectious diseases as well as their severity. In addition, immune responses against hookworm and ascaris, two very prevalent macroparasites, undermine immune responses against introduced diseases like malaria and tuberculosis. This is because the exposure to macroparasites activates the T-helper 2 cell pathway which is less effective than, and antagonistic to the Th1 pathway which stimulates macrophage production to combat mycobacteria and plasmodia. The effects of these persistent and ubiquitous causes are not augmented by the presence of a few scientists in indigenous communities as Tierney claims, but rather by chronic social inequities.
In populations whose adults have never been exposed to nonindigenous pathogens, and who have therefore never developed immunity to them, homozygosity and macroparasitic infection probably exacerbate the effects of infectious diseases on the high mortality that natives experience at contact. To this day, first contacts result in the deaths of between one-third to one-half of native populations within the first five years. Half the Xikrin Indians of Brazil and the Ache of Paraguay died at contact in the 1960s and 1970s. In the state of Rondonia in Brazil, 600 out of 800 Surui died within 6 years of contact in the 1980s. In spite of these well documented examples, in October of 1996, FUNAI officials set out to contact the Korubo, one of 50 groups who still live in isolation in Brazil, with a team of 26 individuals none of whom were medical personnel. But the contact team did include 8 journalists including representatives from National Geographic Magazine. The next year the Korubo attacked a FUNAI follow-up team and they have not been seen since. All the Korubo at that contact could now be dead from diseases introduced by the contact team—all because the scientific literature on contact epidemics was ignored.
After contact is made, biological influences interact with social factors such as sedentism, poverty, and poor access to health care to produce an ever increasing deterioration in health status. Without scientific research on these populations we will never know the full extent of this deterioration, nor how to prevent it. Among the Ache of Paraguay, infant mortality increased over a period of 10 years after contact in the late 1970s. Over that time period, the Ache also became exposed to tuberculosis possibly for the first time in their history. Within fewer than 10 years, the prevalence of active tuberculosis increased from less than 1% to 16% - one of the highest prevalences ever reported for any human population. Some 1800 miles away in Brazil, the Yanomamo are experiencing a similar fate. Within fewer than 15 years, over 6% of the population in some villages became very ill with active tuberculosis during the late 1980s. Because of scientific research, we now have some clues as to why the Yanomamo experience such high rates. A study shows that unlike their Brazilian neighbors, the Yanomamo mount unusually high antibody responses instead of the cell-mediated defense that is most effective in containing mycobacterial infection. This could also be part of the explanation for why the measles epidemic that Neel observed among the Yanomamo in the 1960s was so devastating, and why so many other indigenous groups are similarly affected.
Recent tuberculosis epidemics clearly illustrate that more, rather than less, medical and epidemiological research is imperative to save the lives of indigenous people over the next century. Along with the Ache and the Yanomamo, the Cuna of Panama, the Taraumara of Mexico, the Shuar of Ecuador, the Maka of Paraguay, and many other groups are now becoming breeding grounds of drug resistant Mycobacterium tuberculosis. South American Indians are reliving the experiences of North American natives in the early 1900s. The difference is that we now have ways to cure tuberculosis, and yet the outcomes are currently just as devastating. Indigenous susceptibility to mycobacteria in combination with resource-poor and inadequately managed Word Health Organization-sponsored programs are exactly the sort of conditions that promote the emergence of drug resistance tuberculosis, a sure death sentence in developing countries where specialized treatment costs are beyond anyone’s means. Indigenous people will not survive drug resistance tuberculosis without research designed to find resistant bacilli and health care interventions designed to eradicate them.
Thus, I conclude that international and national guidelines for research among native peoples should be based on scientific understanding of infectious disease epidemiology to serve humanitarian ends. To do so, the field of anthropology needs to denounce anti-science propaganda that attempts to convince indigenous people and Latin Americans to ban scientific research in their communities. These views seem motivated by a desire to control indigenous populations by keeping information and alternative viewpoints from them. That is, these views constitute "colonialism by deception." Adherence to these anti-science views will tragically single out South American Indians as the one population on earth that would give up entirely the right to medical research and intervention, a benefit that is amply enjoyed by people of the First World and its enclaves overseas. This is already taking place. In the 1980s, in the country of Peru we were denied permission to obtain medicines for a remote Machiguenga village because an anti-science local anthropologist who controlled scientific research permits believed that Indians should be allowed to die without modern medical treatment. According to this anthropologist, to do otherwise would constitute meddling with natural and harmonious forms of population control.
I reject the subtext of the Tierney book that indigenous groups and national governments should severely limit scientific activity in native communities. Instead, the field of anthropology needs to make a concerted effort to put First World scientific research to good use by serving humanitarian ends among indigenous people. This can be done by encouraging interdisciplinary research and partnerships with governments in order to end human rights violations and to promote larger investments in native communities. Reporting mechanisms need to be established with international and national authorities that will be responsive to human rights abuses. Scientific partnerships with indigenous people should also be advocated as the Escola Paolista do Medicina has done in Xingu Park over the past 30 years, and research guidelines should ensure that natives can clearly identify fieldwork activities as positive for their communities. Anthropologists and medical scientists should not continue to respond to the plight of indigenous people with silence and complacency but rather with proactive plans of action that include carefully though-out research on indigenous health.
A. Magdalena Hurtado
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