Epidemiologists investigate dynamics of diseases by dvaluating the time-space clusters while cultural anthropologists (ethnologists) study human behaviors how to respond diseases by evaluating socio-cultural background of human life.

The dynamics of diseases must be analysed in the context of human behavior which was appreciated by their cultures and principles. Individual disease pertains a long term influence on cultural aspects of human life. Thus, epidemiologists and cultural anthropologists have often shared their study subjects and undertaken their collaborations for many years.

In this article, the authors at first discuss two historical examples of diseases whose epidemiological reaserches were successfully conducted in aid of cultural anthropologists, and at second part of this article, we introduce our challenge against HIV infection and disease control that is the most important issue to be studied by cultural anthropologist and epidemiologist.

1.Human traits of sickle cell anemia and malaria

The sickle cell trais (SCT) is a genetic disorder of erythrocytes whose traits are distributed throughout India, Middle-East, the Mediterranean and Central Africa. Homozygous SCT dies of severe anemia and thus no children is rerpoduced from the homozygous patients.

In theory of genetics, the SCT decreases its gene frequency in a population. However, West Africans have kept the SCT subpopulation by virtue of malarial infection.

In Allison (1954), an epidemiologist recognized the geographical distribution of the SCT subpopulation in Africa who was resistant to falciparum malarial infection. Libingston (1958), an anthropologist depicted geographical correlation between the positive rate of sickle cell anemia and the linguistic (ethnic) groups. He explained the geographic peculiarity of SCT by migration of people, ecological (subsistence) changes and ecological changes in the environments.

Livingston, F.B. Anthropological implications of sickle cell gene distribution in West Africa. American Anthropologist 60: 533-562, 1958.


He hypothesized that the west Atlantic language-speaking peoples first distributed in the west Africa who had no SCT in their ethnic groups. The other linguistic groups (Kwa language speaking people) migrated to west Africa from east and north-east districs. Two waves of Kwa language-speaking people arrived. The first wave was the Kru and Lagoon-speaking people. They were also non-SCT groups. The next wave was the Akan and Ga-speaking people who resided at the east area of the Kru and Lagoon at present, some of them eventually moved into west Africa. Since the Akan and Ga-language speaking people showd a high SCT frequency, they might be the founder of SCT in the west Africans.

The similar pattern of SCT migration was found among Mande language-speaking people. The Wande people had no SCT but they become SCT carriers after inter-breeding with the west Atlantic language speaking people who were positive for SCT. This interbreeding hypothesis accords with the epidemiological findings of SCT prevalence whose positive rate was increased among west Atlantic language speaking peoples lived at inland as compared with the coastal people.

However, it was not the case among Gambian tropical rain-forest people whose positive rate of SCT was higher in the coastal area than dry inland area. This was related with their ecological (subsistence) condition. In the tropical rain-forest area, they cultivated Yam potatos while the people living in dry area used to work millet cultivation (sorghum etc.). The SCT was increased among Yam-cultivating people and lowered among animal hunting peoples. The high prevalence of SCT was similarly found among Kru and Lagoon subgroups of the Kwa languages-speaking people who cultivated Yam potatos.

Wisenfold (1967), an anthropologist investigated interrelationships among occupation (jobs), sickle cell anemia and malaria. When compared agricultureal products and prevalence of sickle cell anemia, the millet cultivating people was less positive for SCT than rootcrops (yam etc,) cultivating people. Their rootcrops were not the African yam (Diosocorensis cavenesis) but the Polynesian yam ( D.alata, D.bulbife, D.esculenta, Colocasia antiquorum). Added to these they cultured banana and coconut. Wisenfeld called this style of rootcrops cultivation the Malaysian agricultural complex. The Malaysian agricultural complex and SCT showed the same geographic distribution across East to West Africa.In order to understand interrelation between agricultural style and sickle cell anemia, we should know the ecological environment for Anopheles mosquitoes. There are two species of Anopheles mosquitoes in the tropical rain-forest. One species was A.funestus to transmit Plasmodium ovale (malaria) and the other was A.gambia to transmit Plasmodium falciparum. (malaria). The A.funestus could grow in the dark environment of tropical rain-forest and transmit endmic malaria with P.ovale. Meanwhile, epidemic malaria with P.falciparum was transmited by which could growin water holes at sunny place in the tropical forest.

Thus, the endemic malaria (P.ovale) prevailed in the deep tropical rain forest where hanting people lived without any deforestation. However, once these forests were opened to develop Malaysian Yam cultivation, the sunny open environments allowed A.gambiae to grow and transmit P.falciparum to cause epidemic malaria. Inaddition, deforestation bore more agricultural products to increase population density. According to the increased population, Anopheles mosquitoes changed their host range from forest animals to human.

Livingston estimated that agricultural system was introduced to the sub-Sahalian areas 2000 years ago. Thus, the West African people received natural selection pressure to increase frequency of SCT on 2000 years ago and evolved epidemic malaria of P.falciparum.

Weisenfeld developed a computer simulation and successfully evaluated the impact of malarial infection on persistence of SCT among the West African people. It was confirmed that sickle cells became non-permissive to malaria parasites due to sickle cell turnover rate and its altered metabolism.

This comprehensive hypothesis on the interrelationship between sickle cell anemia and malaria infection explained a good model of the biocultinal evolution theory which could unite the fields of epidemiology and anthropology.

2.Kuru and prion disease

REMARK: Today, the "slow virus infection" is understood as prion disease

Kuru was one of the prion disease and Known to be endemic among Central New Guinean high landers. They spoke Fore language. Kuru meant tremoling in Fore language.The patients could not stand up and walk due to a progressive cerebellar ataxia with shivering like tremor and died within several months. Clinical symptoms appeared to be manifsted by a subacute spongiform encephalopathy (Gajdusek 1977).

Berndt, an Australian colonial patrol officer was the first reporter of Kuru. Berndt described Kuru, a psycho-somatic disorder of native people in contact with western cultures.

From late 19C to early 20C, nativistic socio-religious movement called Cargo cult, prevailed throughout the Oceanian countries. Berndt thought that Kuru might be a psychologic disorder of the personal dimension but not a disorder of the social dimension like Cargo movement.

In 1957 Gajdusek came to New Guinea and met Vincent Zigas, a local medical officer. Zigas introduced Kuru diseases to Dr.Gajdusek and explained that background of Kuru disease might be related to the Fore people. This was the first episode on Kuru epidemiology.

The unique symptoms of Kuru, its high lethal rate and predominance of adult fema le patients attracted many investigators.

The Fore belived that Kuru disease was caused by a wrong sorcery which was done by an unfavourable person. The native treatment was how to find out the wrong sorcerer and exclude his sorcery from the patients. The high prevalence of Kuru in 1950-1960 was a disaster which reduced number of women in their society. Male leaders got together and discussed how to exclude the wrong sorcerer the village (Lindenbaum 1979). Fortunately, Kuru faded out after the peak of disease incidence in 1959-1963.

At first most investigators thought that Kuru was a hereditary disease. This hypothesis however was abandoned by the epidemiological findings of Kuru such as outbreak pattern and female predominance.

Next hypothesis was considered from the aspect of nutritional condition under native environments. However, no toxic materials was identified in their foods and water. Botanists and entomologists surveyed biological pathogens but they did not find any possible ones. After they excluded all environmental and genetic factors in Kuru etiology, a new hypothesis (infection hypothesis)was made to explain an etiology of Kuru although the route of infection and mode of transmission remained unknown.

Gajdusek's group was successful to reproduce a Kuru-like disease in chimpanzee after a homo genate of the patient brain tissues was inoculated intracerebrally. Passages of pathological chimpanzee brain tissue reproduced the diseases after several months and years. Thus, Kuru was designated as a slow virus infection on hat time. It was currently renamed as a prion disease. Gajusek was granted the Nobel prize in Physiology & Medicine for 1976.

Kuru attracted investigations in relation to Creutzfeld-Jakob's disease which was thought to be one of the slow virus infections.Kuru has gone before its mode of infection was fully investigated. An etiology of Kuru was considered by cannibalism hypothesis that was speculated by Gajdusek (1977) so as documented in a textbook (McElroy and Townsend 1989).

The cannibalism hypothesis that was speculated by an anthropologist, mislead us to accept a wrong etiology of Kuru. This historical mistake was carefully criticized by Allens (1979). It was also claimed by a Japanese anthropologist that native informants behaved like a cannibal when they met a caucasion anthropologist (Yoshida 1993). This Kuru story was the case of unsuccessful collaboration done by anthropologist who must be an experpert to know people's behaviors and should privide exact informations to epidemiologist. i

3. HIV infection and Cultural anthropology

Informations of the local people how they understand diseases in their epidemic locale, is most important for the HIV prevention and AIDS control. Medical anthropologists called this local information as cultural constriction of illness and recognized it one of the important research fields. This kind of informations was recorded in a natural history of disease of anthropologists.

The natural history of disease should contribute to epidemiology by providinga primary information of the people's behavior to respond diseases. The Cultural constrict of illness was typically seen among Haitian people in the Caribbean Sea.

Former(1990) reported the disease concept on AIDS of central Haitian villagers that was divided by 4 terms from 1984 to present. (1) The first term 1983-1984: villagers believed that the high prevalence of AIDS among Haitian immigrants to USA(1983-1984) must be caused by a Maladi lavil (city sickness). (2) The second term 1985-1986: they thought that AIDS was caused by a move san (bad blood) through their knowledge informed by AIDS champaign of the media and the government. They had no AIDS among the villagers in high land of central Haiti. (3) The third term 1987: The first case of AIDS was found in the village. They saw real symptoms of AIDS such as diarrheas and waning and thought that AIDS was a disease of digestive tract caused by infection with mikwob/microbe. (4) The fourth term 1988- present: AIDS prelailed more and became a common disease in the village. They accepted the concept of infection and use of condom for AIDS prevention. The concept of AIDS was correctly understood by the villagers but some of them believed that AIDS was produced by sorcery or by bacteria-weapon developed by US military power.

Former, an anthropologist explained these popular imege that reflected villagers' anti-government feeling against Haitian dictator and US military powers. Generally speaking, the decease concept of local people was constructed in the context of socio-cultural background. His report pointed a key issue for the comprehensive disease control that was obtained by the local understanding of disease.

Grasp of risk group for HIV infection is another important issue for AIDS control. For instance, clients of sex-workers answered the usefulness of condom to prevent AIDS when they were asked by interviewers, but they did not use a condom in their real intercourse.

Leonard explained this behavioral discrepacy by the following reasons; male clients appreciated feracio during intercourse with prostitute and want to have a clean intercourse with a young lady who was immature in her sex business and not use a drug. The belief rendered male clients to accept a risky intercourse.

The singles bar is a drinking place to discover a sex partner irrespective of homosex and heterosex. The customers are at high risk for sexually transmitted infections and diseases by their nonspecific sex intercourse.

Stall et al.(1990) investigated his San Francisco cohort study of 1500 cases of customers of single's bar and pointed that they had a plenty of knowledge of AIDS, but they easily behaved a risky intercourse. Prostitutes and customers of singles bar often conducted a contradictory behavior in spite of their ample knowledge of disease. The increase of knowledge was insufficient to control disease and thus the individual behavior must be changed to prevent risky action.

Epidemiogical study on US drug-users revealed a high prevalance of HIV seroposivies among intravenous drug users (Page et al.1990). Illegal drug users shared a needle at a shooting gallery which was hidden from police control. The ethnographic survey informed that sharing of needle encouraged mutual confidence at the shooting gallery. They were willing to share a common needle. Page et al (1990) recommended to use a sterilized needle and quit sharing of needles to prevent HIV infection and disease.

For HIV prevention and AIDS control, cultural anthropologists can support epidemiologists to record people's behavior and collect the sosio-cultural background of AIDS riskgroups. To this end, we should advise people not to take risky　behavior in addition to medical knowledges on HIV and AIDS. Changed behavior of the risk groups could be established by exact knowledges from real observations and interviewed documents of their sosio-cultural background.

Conclusion

Epidemiology is comprised of three paradigms; descriptive, analytical and clinical ones which investigate dynamic changes of diseases in time and space as well as multifactorial development of diseases. Epidimiology of 1950s was the descriptive epidemiology which depicted infections and acute diseases. In 1950-1970, the analytical epidemiology was a major discipline to investigate a risk factor of epidemiology needed theoritical supports of cultural anthropology to analyse the nature and cultural factor of human behavior.

Causal relation of sickle cell traits and malaria revealed by the studies of Livingston (1958)　and Wisenfeld (1967)　was monumental success story in the time of two paradigms. In contrast, the Kuru study of Fore was only successful to persuade the viral etiology but it was unsuccessful to establish the cannibalism hysothesis proposed by anthropologists. This hypothesis was not appreciated anymore.

is unacceptable at present scarsely and. The latter was were not appreciative in the current evaliaticoen. After middle of 1970s, the clinical epidemiology was a trendy paradigm which aimed to assess clinical practice of intervention study by introducing operations research and decision making theory. Thus, the clinical epidemiology mainly used a mathematical model that appreciated less cultural and social factors and became one of the field to study a particular factor of diseases. In these years, the holistic approach of classical anthropology became unpopular among epidemiologists. Thus, epidemiologist was not interested with holistic approaches by classic anthropologists.

from middle 1980s to present, HIV infection and AIDS control was the major issues of epidemiological study. Now, the cultural-anthropological approach revived again to consider cultural background of sex behavior and drug abuse. In order to face a global problem of AIDS, some cultural anthropologists are changing their classical holistic theory to more practical approach of the behavioral science. These epidemiological anthropologists pay attention to psycho-social condition and non-infectious diseases (Jane et al. 1986). Both epidemiology and cultural anthropology continue to change their research styles but keep their mutual interactions. In conclusion, the continued collaboration between epidemiology and cultural anthropology will open a new frontier of human science.

Refences

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• Ingstad,B. The cultural construstion of AIDS and its consequences for prevention in Botswana. Med Anthropol Quaterly NS 4: 28-40, 1990.
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• Lindenbaum, S. Kuru sorcery: Disease and danger in the New Guinea highlands. Palo Alto, CA. Mayfield, 1979.
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• Stall, R. et al. Sexual risk for HIV transmission among Single-Bar patrons in San Francisco. Med Anthropol Quarterly NS 4: 115-128, 1990.
• Wisenfeld, S.L. Sickle cell trait in human biological and cultural evolution, Science 157:1134-1140, 1990.
• Yoshida, S. Minzokugaku to Ekigaku (Ethnology and Epidemiology: in Japanese) Igaku no ayumi 165(1): 8-12, 1993.