Diseases and Disease Ecology of the Modern Period in Southeast Asia

Southeast Asia can be visualized as the part of Asia that spills into the sea, comprised of long coasts, tidal plains, peninsulas, and islands. There are high mountains, inland plains, plateaus, and upland valleys; nonetheless, to a very large degree, human culture has developed with an acute awareness of water, from the sea, the rivers, and the monsoon rains. It is therefore not surprising that many of the endemic health problems in the region are related to water; indeed, since prehistoric times, nearly all major areas of habitation have been exposed to global contact by water transport.

Maritime routes linking the littoral civilizations of the Eurasian landmass have passed through Southeast Asia for more than two millennia. We can accordingly assume that from early times the region experienced all of the epidemic diseases familiar to the ancient world. What inhibits discussion of diseases in the earlier historical periods of Southeast Asia is the lack of data. Because of the prevailing tropical-equatorial climate, the preservation of written records has, until recently, required greater effort than most human societies were prepared to make. Our first information comes from the observations of Chinese annalists, whose works survived in the temperate climate of northern China. As the Chinese moved southward into what is today northern Vietnam, they recorded perceptions of disease associated with what for them were southern lands.

Most prominent among the health problems encountered by ancient Chinese armies in Vietnam were malaria and other "fevers" associated with the monsoon rain season. Chinese generals timed their expeditions into Vietnam to coincide with the dry season, from November to May. When, in 542, ill-informed imperial officials ordered a reluctant army to move into Vietnam during the rainy season, 60 to 70 percent of the army was soon reported dead from fevers (Taylor 1983). Earlier, the general of a Chinese army encamped in Vietnam during the rainy season of A.D. 42 described the scene as a kind of exotic hell: "Rain fell, vapors rose, there were pestilential emanations, and the heat was unbearable; I even saw a sparrowhawk fall into the water and drown!" (Taylor 1983).

It became customary for Chinese generals to explain their failures in Vietnam in terms of "miasmal exhalations" by which they associated the heat and humidity of the area with disease. One of the most famous episodes of disease among soldiers was in 605 after a Chinese army successfully plundered a Cham city in the vicinity of modem Da Nang, on what is today the central coast of Vietnam: The army nearly disappeared when it was struck by an epidemic on its return northward (Taylor 1983). This disease was not malaria, but may have been cholera, smallpox, or possibly even plague. In 627, a prominent Chinese official refused an imperial order to serve as governor of the Vietnamese territories on the grounds that in Vietnam "there is much malaria; if I go there I shall never return." He ultimately chose to be beheaded for insubordination rather than accept the assignment (Taylor 1983). Previously in 136, a Chinese official had argued against sending an army to Vietnam because, among other reasons, the anticipated losses to disease would require the sending of reinforcements who would be disaffected at being ordered into a pestilential region (Taylor 1983). The failures of Chinese invasions against Vietnam in 980-1 and 1176-7 were accompanied by large losses of manpower to malaria.

Generally, malaria has never been a serious problem in preurban lowland areas where waterworks are kept in good repair and the population is at peace (Fisher 1964). Those species of anopheline mosquitoes that breed in the swamps, irrigation canals, and ricefields of the lowlands tend to prefer the blood of animals; and since animals are not susceptible to human malaria and therefore do not provide a reservoir for the disease, these mosquitoes normally do not carry malaria (Stuttard 1943). On the other hand, those species of Anopheles that breed in the shady, cool water of streams in the foothills and mountainous areas are strongly attracted to human blood and are dangerous vectors of malaria (Stuttard 1943; Fisher 1964).

Chinese armies entering Vietnam by land must pass through upland areas where malaria is endemic. This fact, along with the desire to achieve the advantage of surprise, explains why Chinese generals, having had the luxury of water transport and enough time to lay plans without haste, preferred to invade Vietnam by sea (Taylor 1983). Malaria became a threat in populated lowlands only when warfare or other disorders led to large-scale slaughtering of animals, a scattered population, and a breakdown of the water control system (Murphy 1957).

Beginning in the late nineteenth century, malaria became a problem on a larger scale than had been previously known because of circumstances associated with the development of colonial and semico-lonial economies. These included the improvement of communication systems, large-scale population movements, the opening of new ricelands, and the extension of urban settlement. All of these changes required relatively large-scale construction and engineering projects that opened new areas congenial to certain mosquito species and to epidemics that decimated cattle populations, thereby turning mosquitoes toward human beings (Boomgaard 1987).

In the early 1950s, when the Malayan emergency resulted in the resettling of large numbers of people into crowded lowland camps, an observer noted that the health of the population improved the farther upriver one went; the same observer argued that upland peoples who had been resettled in more densely populated areas near the sea experienced an "accentuation of an already existing pattern of disease" as a consequence of "the loss of interest in life due to the breakdown of the old culture" (Polunin 1952). It may be that any disease ecology must also take into account the political and psychological conditions of a population.

Another observer has claimed that cultural factors can be important in the experience of disease and illness, that there is a relationship between disease and social marginality, and that the incidence of disease can operate as a mechanism of social control enforcing respect for authority. In fact, he has written that "the social system tends to precipitate events which validate the medical beliefs, and this in turn affirms the principles upon which the social structure is based" (Feinberg 1979). It is relatively easy to discuss this approach in relation to the practice of medicine in premodern societies (Lan-Ong 1972), but contemporary attitudes toward modern medicine tend to resist this line of analysis.

Beginning in the tenth century, Southeast Asians began to record observations and write annals that provide local information, first in Vietnam and eventually in Thailand, Burma, Cambodia, and Java. Epidemics are mentioned regularly, particularly in times of warfare, though it is very difficult to determine with certainty what diseases were being observed. Some modern researchers believe that cholera was absent from Southeast Asia until the 1820s, and bubonic plague was likewise absent until 1911. The evidence, however, is ambiguous (Boomgaard 1987; Hull 1987; Terwiel 1987; Reid 1988). The great outbreaks of cholera and bubonic plague in the nineteenth and twentieth centuries were apparently related to the circumstances of European colonial expansion in the region and represented a more virulent experience of these diseases than can today be imagined for earlier times. Southeast Asia's historic openness to maritime trade and the global contacts that went with it surely resulted in a measure of immunity being built up in the population against the diseases common to international entrepots.

A relatively dispersed village settlement pattern and the Southeast Asian habit of bathing frequently are two other factors that appear to account for what has been called the "relatively mild epidemic cyle" in premodern times (Reid 1988). The most serious epidemic disease, according to Siamese chronicles from the fourteenth century and European observers in the sixteenth and seventeenth centuries, was smallpox (Terwiel 1987; Reid 1988). Leprosy and yaws also figured prominently in early European perceptions of disease in Southeast Asia, probably because of their disfiguring effects (Reid 1988). Plague, according to French observers in Indochina, was found only where there were large numbers of Chinese, namely port cities with a concentration of ships, large stores of grain, and consequently an abundance of rats (Stuttard 1943). In the 1960s, by which time plague had been eradicated in most of Southeast Asia, outbreaks still occurred in Vietnam as a result of wartime conditions (South East Asian Regional Centre for Tropical Medicine 1967).

From the 1960s, there has been a growing literature enumerating and analyzing diseases in Southeast Asian countries, particularly Thailand. The category of "tropical diseases" is sometimes used to emphasize that most of the health problems encountered in the region are now seldom seen in temperate climates. The 1967 syllabus of the "tropical medicine" course at Bangkok's University of Medical Science, Faculty of Tropical Medicine, covered the following illnesses, all identified as "common diseases": (1) viral, such as smallpox, rabies, dengue, hemorrhagic fever; (2) rickettsial, such as typhus fever; (3) bacterial, such as typhoid fever, bacillary dysentery, food poisoning, cholera, leprosy, and plague; (4) spirochetal, such as amebiasis, malaria, kala-azar, and giardiasis; (5) helminthic, such as hookworm infection, ascariasis, trichuriasis, enterobiasis, strongyloidiasis, gnathostomiasis, filaria-sis, fasciolopsiasis, and paragonimiasis; (6) nutritional, such as protein-calorie deficiencies, mineral and vitamin deficiencies, and food toxicants; and (7) miscellaneous, such as effects of heat, heat exhaus tion, blood diseases of the tropics, hemoglobinopathies and other genetic factors, as well as snake and other venomous bites (South East Asian Regional Centre for Tropical Medicine 1967).

In the same year, South Vietnamese disease specialists identified malaria and plague as their greatest problems and categorized "endemic infections" as follows: bacteriological (cholera, salmonellosis, bacillary dysentery, and typhoid), parasitic (amebiasis, ascariasis, hookworm infections, gnathostomiasis, strongyloidiasis, diphyllobothriasis, spargano-sis, and taeniasis), viral (hemorrhagic fever and dengue fever, smallpox, infectious hepatitis, Japanese B encephalitis, and rabies), bacterial (leprosy and venereal diseases), and mycotic (cutaneous mycoses) (South East Asian Centre for Tropical Medicine 1967).

What can be emphasized is that a very large percentage of these diseases are waterborne or are transmitted by a parasite that depends upon a water-dwelling host such as the snail. In a region where a large part of the population is involved in paddy agriculture requiring barefoot work in fields covered with water, where sanitation depends upon the common use of rivers and ponds, and where nearly half of each year is a time of heavy rainfall, such diseases account for much of the burden of unhealthiness. Dysentery, amebic infections, intestinal worms, and skin afflictions are endemic. The linkage between health and seasonality is obvious to any observer and has been an object of study in recent years. The wet season, in addition to providing an environment in which many disease vectors thrive, is also a time of food shortages and of a consequent relative increase in poverty and decrease in physical well-being. Women and children are particularly at risk during this time (Charles 1979). This writer was in Hanoi in May 1986 during the onset of the rainy season and saw that within a few days a large part of the population had become ill with fevers and other "flu" symptoms; local people considered this a normal phenomenon.

Medically trained observers in Southeast Asia have difficulty in determining mortality statistics. Such compilation efforts are complicated by the fact that although death may be occasioned by the onset of a particular disease, such as malaria, the person's inability to resist the disease is generally due to prior debilitation from a combination of other afflictions, such as intestinal parasites and nutritional deficiencies (Institute for Population and Social Research 1985).

Beriberi, caused by vitamin B deficiency, was in premodern times largely confined to the islands of eastern Indonesia where sago rather than rice was the main dietary staple (Reid 1988); recently, however, it has become a more general regional phenomenon as a result of the increasing use of polished rather than whole-grain rice (Fisher 1964). Beriberi was first reported by the Portuguese in Southeast Asia during the sixteenth century, and the term is of Malay derivation (Reid 1988).

The ecology of disease in Southeast Asia is currently in a period of rapid and significant change, the beginning of which is usually dated around 1970. For one thing, except for infants and children under 5 years, infectious diseases are no longer a significant threat to health. Tuberculosis remains a hazard for the aged population (which has grown), and malaria remains endemic in many areas, but, in general, tuberculosis, pneumonia, malaria, diarrheal diseases, and nutritional deficiencies, along with other infectious diseases, have declined. On the other hand, death rates for heart-related diseases, cancer, and accidents along with violent deaths have significantly increased (Institute for Population and Social Research 1985). Increasing attention is being given to the problem of infant mortality, for persons under 5 years have benefited least from the overall improvement in health. Diseases of pregnancy, delivery, and puerperium have also become more prominent of late. In addition, cirrhosis of the liver and hepatitis have appeared as significant health problems (Institute for Population and Social Research 1988).

The rise in noninfectious diseases, namely coro-nary-cerebrovascular diseases and malignant neoplasm (cancer), is primarily a phenomenon of the large urban centers such as Bangkok. It is believed to come not only from improvements in diagnosis but also, in the words of a Thai government report, from "real increases in the incidence rate due to various environmental hazards of the present living conditions" (Kanchanaraksa 1987).

Larger proportions of the populations of the Southeast Asian countries are increasingly concentrating in major urban centers. Living conditions in these places are increasingly exposed to the chemical environment of modem industry and to the emotional pressures of modem business activity. As Southeast Asia is integrated into a global system of manufacturing and markets, we can expect that its disease ecology will begin to display characteristics already familiar to areas where this system has been in place for several decades.

Keith W. Taylor

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