Studies on Malayan Filariasis in Che-Ju Island, Korea

Abstract

Although 14 species of mosquitoes were collected in Che-ju Island, Korea in August and September, 1970-1972, dominant mosquitoes feeding on man around dwelling houses were Culex pipiens pallens and Aedes togoi. Natural infections with infective larvae of Brugia malayi were demonstrated only in Ae. togoi. It is considered from these facts that the main vector of malayan filariasis in Che-ju Island is Ae. togoi. Anopheles sinensis which is known as the vector of malayan filariasis in other areas does not seem to act an important role in the transmission in Che-ju Island, because the desnity is very low owing to the scarcity of suitable breeding places. The period for the larvae of Brugia malayi to mature in Ae. togoi was estimated to be between 6 and 9 days from the results obtained by dissecting the females of the mosquito reared in the laboratory for various days after the collection at houses with microfilarial carriers. This period is much shorter than in the case of Wuchereria bancrofti. The breeding of Ae. togoi was observed mainly in rock pools on the seacoast, and only very rarely in artificial water containers within villages. Generally, adult females of this mosquito were abundantly found at houses near to the seacoast, and the density decreased with the distance from the seacoast. Similar tendency was seen in the distribution of the patients of malayan filariasis. Che-ju Island, Korea, which is 1,820 km2 in area, is situated about 370 km southwest west to Tsushima Islands, Japan. In the center of the Island there is a mountain with an altitude of 1,950 m and the plain area is rather small so that rice fields are not much developed. Human filariasis caused by Brugia malayi is known to distribute densely in the Island, in which mosquitoes were studied in 1970, 1971 and 1972 in relation to malayan filariasis. The results obtained will be reported in this paper, as the second part of studies on malayan filariasis in Cheju Island, Korea.

Studies on Malayan Filariasis in Che-Ju Is., Korea

“…It is generally accepted that Ae. togoi breeding in rock pools on the seacoast is the main vector of B. malayi in the endemic areas of Che-ju Island Wada et. al, 1973), whereas Anopheles sinensis is suspected to be a probable vector in the inland Korea (Kim et al, 1973).…”

“…In Che-ju Island, Korea, only the periodic form of B. malayi is known to cause filariasis in man; the main vector is Ae. togoi (Wada et al, 1973).…”

Introducing activities of the Archives of Infectious Diseases History (AIDH) project: Historical epidemiology

“…It was very important that the main vector in Cheju Islands was also Aedes togoi . At the joint-control program for lymphatic filariasis in Cheju Islands around the 1970s between the Nagasaki University and the Seoul National University, both scholars also researched the mosquito species and found out the main vector of Brugia malayi was Aedes togoi [ 29 ]. This kind of analysis is not the direct evidence that the Ama divers were the reason that the Brugia malayi was only in Hachijo-koshima.…”