The morphological characters of the microfilaria of Brugia malayi collected in Cheju-Do, Korea were described and compared with those or other local strains, already reported from the Malay Archipelago(Brug, 1927), Huchow, South China (Feng, 1933), Hachijo Kojima, Japan (Hayashi, 1951) etc. And it was found that there are no marked difference among these kinds of Microfilaria malayi. The percentage measurements of the fixed points in the Microfilaria malayi from Korea are summarized as follows; B.N.C.: 3.38%(2.90-3.72%), N.R.: 22.64% (17.36-25.81%), E.P.: 32.26% (27.49-36.60%), E.C.: 38.78% (34.90-41.72%), Inn. K. begin: 53.95% (49.50-58.84%) end: 67.87%(63.02-72.97%), G-1: 70.42% (60.22-75.23%), G-2:76.70% (75.10-78.32%), G-3:78.84% (77.81-79.59%), G-4:80.84%(79.82-81.35%), A.P.:82.94%(77.32-89.72%), Length: 193.39(+-12.3 micro-meter)(170.77-233.08 micro-meter), Width: 7.04+-0.37 micro-meter(5.99-7.99 micro-meter), Sheath: 268.48+-17.07 micro-meter(218.72-286.47 micro-meter), Ratio(Cephalic space): 1: 0.78
parasitology-helminth-nematoda ; Brugia malayi ; microfilaria

An epidemiological study on brugian filariasis was carried out in endemic areas including Cheju Island in Korea, with a brief review of literatures.The results showed that the incidence among residents has remarkably decreased in Cheju Island, which was the main endemic area. Reviewing available informations on the prevalence of filariasis reported in recent years and also judging from the present socio-economic conditions which enable people to practice personal protection against mosquitos, it can be said with confidence that filariasis has almost disappeared from Cheju Island and inland areas. The disease is considered to remain at a low level of endemicity in Hugsan Islands. Certainly mass diethylcarbamazine (DEC) treatment carried out in Cheju Island in the 1960s and 1970s and remarkable economic growth followed by improved living standard and altered life-style of inhabitants could all have combined effects on the disappearance of this mosquito-borne diseae in this island. If the present trends go on, the possibility of resurgence of filariasis in Cheju Island is hardly postulated.
parasitology-helminth-nematoda ; Brugia malayi ; filariasis ; epidemiology

With a purpose to find out natural transition of endemicity of Malayan filariasis in inland Korea, a survey was conducted in June 1980 in Isan-Myeon of Yongpung-Gun (former Yongju-Gun) where an epidemiological investigation had been carried out in 1973 without any control activities such as chemotherapy. Five sample villages were surveyed for microfilaremia by 20 microliter night blood examination among inhabitants and the results of the surveys conducted in 1973 and 1980 were compared to determine natural transition of the endemicity of malayan filariasis during the period of the last 7 years. The current microfilaria rate among inhabitants in the 5 villages was 2.2 percent on the average (male: 1.6 percent, female: 2.8 percent) from 370 persons examined. By village, the rates were 5.9 percent (number of persons examined: 34) in Baranggol, 0 percent (30) in Guitonggl, 4.2 percent (72) in Alseonggol, 0 percent(65) in Jangjagol and 1.8 percent (169) in Saehae. Extremely low microfilaria rate was noted in young age groups. By age group, no positive case was found in those age groups below 30-39 years except 10-14 age group in which 2 positives (4.4 percent) were found. Two positives each were found in the respective age groups of 40-49(3.2 percent), 50-59 (4.4 percent) and over 60 (3.4 percent). In evaluation of the natural transition of the endemicity during the period of the last 7 years, the microfilaria rate turned out from 13.1 percent in 1973 to 2.2 percent in 1980. The difference in the microfilaria rate was 10.9 percent and the natural reduction rate per year was 1.6 percent on the average. From the examination of 35 cases which had revealed microfilaremia 7 years ago, 85.7 percent(30) of them were found to have converted to microfilaria negatives. On the other hand, from the 151 cases which had revealed no microfilaria in 1973, only 0.7 percent (1) of them was found to have converted to microfilaria positive. In the intensity of microfilaremia, the number of microfilaria/20 microliter blood per positive case was 11.0 in 1973 and 9.1 in 1980. The number of microfilaria/20 microliter per examinee was 1.4 in 1973 and 0.2 in 1980, thus reduced to 1/7 during the period of the 7 years. The retarding endemicity of malayan filariasis in inland Korea was considered to be resulted in by the gradual increase of environmental factors in relation to ecology of vector mosquitoes, which adversely affect to the transmission of malayan filariasis. Followings are suggested to be the factors which control the transmission of the malayan filariasis in this area: Inhabitants are the only natural final host of Brugia malayi infection in this area, gradual elevation of living standards of the inhabitants, gradual awakening of consciousness and behavior among inhabitants to protect themselves from mosquito biting using such as mosquito nets and insecticide sprays, preference of animal bait of vector mosquitoes, Anopheles sinensis, increase in number of domestic animals and fowls being raised in the village areas which play a major part of blood donors to vector mosquitoes, and relatively short (3-4 months) period of mosquito season in a year.
parasitology-helminth-nematoda ; Brugia malayi ; epidemiology

The clinical manifestations in filarial infection were examined during 1965-1966 from the known endemic areas: Yongju, a mountainous inland area and Cheju-Do, an island. All the microfilaria which were found during the survey were Brugia malayi. The principal symptom was cuticular hypertrophy (elephantiasis). It was found in 4 cases from Yongju among 707 villagers, 84 cases from Cheju-Do among 2,376 villagers. Four microfilaremia cases (4.5%) were found among a total of 88 cases of elephantiasis. In Cheju-Do, the higher incidence of elephantiasis was observed among people over 20 years old and the females showed much higher incidence than males (30 males and 54 females). The cuticular hypertrophic changes (elephantiasis) appeared more often in the lower extremities(77%) than in the upper part of the body, and in the right side than in the left.
parasitology-helminth-nematoda ; Brugia malayi ; filariasis ; hypertrophy

The periodicity of the microfilariae of Brugia malayi was studied in 9 human carriers from Shin-san Ri, Seong-san Myon, Cheju Island. The periodicity pattern was markedly nocturnal and the peaks were observed between 21:30 p.m. and 5:30 a.m. The average peak count was 1:30 a.m. and the percentage of peak count at this time was 95.3. The ratio of minimum of the average peak count percentage to the maximum was 8.3. The periodicity pattern of B.malayi in Cheju Island was compared with that in Inland and no differences were found between two forms. From the above observations, it was concluded that the periodicity of B. malayi in Korea is markedly nocturnal and closely resembles that in the strain of Penang, Malaya.
parasitology-helminth-nematoda-Brugia malayi ; periodicity ; microfilaria

A night blood survey was carried out among inhabitants aged over 1 year from the fifteen villages throughout Cheju-Do (Quelpart Island). Blood films from 2,139 persons were examined and 183(8.6 percent) showed microfilariae, the incidences varying according to geographical sources are from 0.8 to 19.5 per cent. All the microfilariae found in this survey were of the nocturnal periodic Brugia malayi. The microfilarial density was 1.9 per cent of blood. The age and sex distributions of microfilaria rate in Cheju-Do were not distinctly different. On the other hand, the intradermal test using Dirofilaria antigen (FPT antigen) and clinical survey of filariasis were also undertaken in same areas of microfilaria survey. Out of 2,449 inhabitants examined 1,434(58.6 percent) persons showed positive reaction of skin test, 503(20.5 percent) persons have clinical manifestations and 112 (4.6 percent) persons showed elephantiasis . It is assumed that Aedes togoi may be the most probable vector of B. malayi in the areas of Cheju-Do.
parasitology ; helminth ; nematoda ; Brugia malayi ; epidemiolgy ; filariasis ; intradermal test ; blood

A study on the effect of diethylcarbamazine (DEC) (Supatonin) against Brugia malayi infection was conducted on Cheju Island in September 1965. A total of 182 persons living in a village of Aiwol Myun, Bukcheju-Gun was examined for microfilaraemia. Microscopic examination of smears of 20 microliter of blood revealed a microfilaria positivity rate of 28.5 per cent. At the end of September 1965, 34 confirmed microfilaria positive cases were treated with DEC at a daily dosage of 5 mg/kg body weight. A full course of 12 days of drug administration divided of two rounds for 6 days each was used. The first round of treatment was given under a strict supervision of the author in order to observe carefully side-effects of the drug. The second round of treatment was given in January 1966. The microfilaria density in 20 microliter of blood of those who received the drug was checked four times; before the treatment, during the first round of the treatment, 2 weeks and 4 months after the completion of the first round. The pre-treatment mean microfilaria density of 104.6 diminished to nearly zero (only two cases with one microfilaria respectively) 2 weeks after the first round and again slightly rose up to 0.5 four months after the first round. These results indicate that DEC (Supatonin) is highly effective to eliminate the microfilaria of B. malayi. However, severe side-effects, e.g. fever (average 38.6C, maximum 39.7C), headache, backache and seldom abdominal discomfort ect. were observed. There were two cases of withdrawal from the scheme due to refusal.
parasitology-helminth-nematoda ; Brugia malayi ; chemotherapy-diethyl carbamazine ; diethylcarbamazine

The species composition, population density, and seasonal prevalence of vector mosquitoes in an inland area of Kyungpook province were studied, based on light trap and human bait trap collections, and the recent patterns of infestation for infective larvae of Brugia malayi in these vector hosts were investigated from May to November in 1985. Nine species in four genera of mosquitoes were collected by light trap, human bait trap, and/or by nets. Anopheles sinensis Wiedemann was the most abundant species collected by light traps during this year. Culex tritaeniorhychus Giles was the second abundant species, and Aedes vexans nipponii(Theobald) ranked third in total abundance. The earlist time when A. sinensis were found was the middle of May. At that time the temperature ranged from 14.3 C to 22.8 C and the humidity 53-90 per cent. The month of highest average nightly catch was July, when the temperature was betweeen 21.5 C and 30.6 C and the humidity 72-91 per cent. The peak time of biting activity of mosquitoes was different in each month, i.e. between 22:00-23:00 in July, and 20:00-21:00 hours in September, when the temperature was between 24.3 C and 26.5 C and the humidity 73-88 per cent in the field. While infective larvae of B. malayi were reported to have been found in one species of mosquito in 1975, no larvae were found in any species collected in this survey.
parasitology-helminth-nematoda ; arthropoda ; Brugia malayi ; Anopheles sinensis ; epidemiology

Study of filariasis to determine important factors involved in its ecology was carried out on Che Ju Island for three consecutive years from 1968 to 1970 in seven villages, three coastal villages and four islets remote from the main island. One village which was located in mountainous area far from the coast was surveyed to serve as control area. About 90% of population inhabiting the study area had at least one blood smear during the three-year period; about one third had three blood smears, and a little over one third had two, and the rest only one examination. Animal and mosquito surveys were carried out at the same period. Followings are the results obtained: All human cases but several had microfilariae identical to the description of B. malayi. The several cases who had morphologically different microfilariae from that of B. malayi need further study for definite conclusion. Five persons randomly sampled from Mf positives and bled every two hours demonstrated nocturnal periodicity between 9 p.m. and 3 a.m. Human is considered to be only reservoir host for human filariasis in the area since animal survey and experimental exposure to the infective larvae of human filaria species showed failure to infect animals. Microfilaria rate, microfilaria density, prevalence of elephantiasis varied by area and age with correlation, which indicated cumulative process of the parasite by repeated exposure and development of host immunity to certain extent. Clinical manifestation of filariasis (symptom complex and elephantiasis ) taken from history and inspection was low in its prevalence with range of 0.9% 11.8% of total population. Only 5.2% of 517 Mf positives had the clinical manifestation. 24.8% of 109 persons with clinical manifestation had microfilaria; 42.9% with symptom complex only, 23.1% with both symptoms and elephantiasis, and none with elephantiasis only were microfilaria positive. Ae. togoi was the only species infected with the filaria. Mosquito infection rate by area showed positive correlation to the Mf rate and density of human population; where the Mf rate and density were high, the mosquito infection rate also high.
parasitology-helminth-nematoda ; ecology ; epidemiology ; Brugia malayi ; filariasis

Control programme of malayan filariasis by diethylcarbamazine was set up in village, Cheju-Island, Korea. The daily dose of 6 mg per kg of body weight for 6 days was chosen as a chemotherapeutic course only for microfilaria positives, which was repeated with an interval of one or two months. For the evaluation of drug control programme the yearly posttreatment blood survey was carried out. The results collected from 1970 to 1973 were analysed from the various points of view, such as microfilaria positive rates, incidence as well as prevalence rates. The change of microfilaria counts was also utilized for the comparison of the intensity of infection among population in the four year blood surveys. Considering the extremely skewed distribution of average microfilaria density, the mode of frequency distribution of microfilaria density in a population was particularly taken into account for the evaluation of changing endemicity affected by diethyecarbamazine treatment. The equation; Y= a+b log X(a , b: constants, X=microfilaria density; Y=probit scale of cumulative frequency of positives to X microfilariae) was found to fit farily well the data collected from four-year surveys before and after treatment. From these data obtained, four regression lines have been drawn by determining "a" and "b"; two paramenters, which were increased year by year since inauguration of control programme. In the present investigation, it was verified that the chmotherapeutic control measure of malayan filariasis applied in a village of Cheju-Island has been successfully carried out and the quantitative level of endemicity inthis area has also been distinctly lowered within the four-year control programme.
parasitology-helminth-nematoda-Brugia malayi ; chemotherapy-diethylcarbamazine ; control ; filariasis ; diethylcarbamazine