MALARIA AND THE INHABITANTS OF THE YAEYAMA ISLANDS, OKINAWA, JAPAN

Abstract

PURPOSE AND METHOD OF THE STUDY
Malaria in the Yaeyama Islands was a typical endemic disease of the Okinawa region, and was long known for its violent symptom especially high fever. This malaria was not a simple intermittent fever but a type of malignant tropical malaria carried by the Anopheles minlmus mosquito. It is the very point to be noted that thiss sort of mosquito is only found in Yaeyama within the whole territory of Japan. As expressed in the author's paper on the “Chang-li” or the malignant tropical malaria in South China, he could not make any field survey but only use some of Chinese literatures in Japan's libraries. This paper, however, is largely based on the author's observations about the actual conditions of the tropical malaria in a field similar to South China.
The author analyzes the geographical causes and effects of the endemic disease, and tries to explain the regional structure which facilitates the outbreak of the disease in the Islands. The method of this study mainly follows the historical-ecological one. Fortunately he could receive many fruitful instructions from Dr. S. Ôhama, discoverer of the Anopheles ohamai, another mediator of the malignant malaria, and a local old historian E. Kishaba. He took many data from the accounts of an explorer G. Sasamori at the end of the 19th Century.
HISTORICAL PROCESS OF THE OUTBREAK OF MALARIA IN THE ISLANDS
Population of the Yaeyama Islands was growing up to 1771, when the terrible high waves attacked these islands. This big tsunami, called the Meiwa Tsunami, swept out about 1/3 of the inhabitants of the Islands, but did not wipe off malaria. On the contrary, the malaria attacked severelyy about half of the Islands and the whole population of Yaeyama began to drop down in number from this time to the early years of the Mei j i Era, in spite of the efforts to increase food production by establishing new villages. Many historians of Okinawa point out that the establishment of these new villages was a policy of the government of Ryûkyiû Kingdom which was led by Saion, a well-known politician of Ryûkyû, to collect foodstuff for the Main Island of Okinawa which was almost void of rice fields. The system of food collecting was to pay the tax not in cash but by rice per male adult.
The new villages were established near the arable lands possible for paddy rice growing. The main cause for population decrease was the outbreaking of malaria in the paddy fields. The government continued to supply new labourers from uncontaminated villages to the villages which were showing population decrease until the Kingdom was annexed to Japan. But the hard system of rice tax dissipated the energy of inhabitants thoroughly, and they could not stand against the disease.
Until the middle of the 20th Century, very few people lived in the hilly areas of the Islands because of the fever. Just before the end of the Pacific War, in 1945, all dwellers of the Islands were compelled to move into the area of malignant malaria by the order of the Japanese Army to protect themselves from the attack of the American force. A result was the pandemy of malaria from which a half of the people of Yaeyama suffered and 1/5 of the half were put to death.
THE ECOLOGICAL AND MEDICAL ENVIRONMENTS OF MALARIA IN YAEYAMA
The inhabitants in Yaeyama call this disease “yakii, ” meaning “burning.” They know that this fever tended to break out after staying several days near a brook or spring to cultivate paddy fields. The Islands are consisted of two main islands, Iriomote and Ishigaki, which occupy more than a half of the paddy fields in Yaeyama, whereas several other small coral islands had been used by the majority of the inhabitants. Therefore, the Islands are divided into two: the healthy dry region and the unhealthy wet region where the Anopheles mosquito is easily bred.