Epidemiological and clinical studies on malayan filariasis in Cheju-do, Korea
A considerable amount of work has been done regarding the filarial worm in Korea,
since Yoon(1927) found one male filaria from the left inguinal lymph gland by
autopsy of one case with elephantiasis of both legs. although Yoon(1927) identified
the parasite as Wuchereria bancrofti without any morphological study, it is the
general opinion that Brugia malayi is generally recognized as the only species of
human filaria in Korea. The malayan filaria is distributed predominantly in Cheju
Island and its neighbouring islands, though several areas in the mainland also show
endemicity.(Oh, 1929; Oh, 1930; Bun, 1939; Senoo, 1943; Hunter et al.. 1949; Paik,
1959; Lee et al., 1964; Hwang et al., 1965; Soh et al., 1966 and Seo et al., 1968
The present study was designed to elucidate the epidemiological and clinical
features o B. malayi infection in Cheju Island.
As the subjects, 981 students of Seogi Agricultural High School and Seogi Girl's
High School(male, 257; female, 724) at Seogipo-Up(=town) were sampled in May, 1970.
For the second step, samples were drawn among 521 students of Namwon Junior High
School(male, 302; female, 219) and 164 school children(male, 97; female, 67) of
Wimi Primary School located together at Namwon-Myun(=township), where high positive
rates were calculated from the above survey at Seogipo-Up.
Seven elephantiasis cases and six control inhabitants besides the students were
also selected for some physiological investigation.
The students gathered voluntarily at the period of 21:00∼23:00 hours. Three
drops of blood from the examinees' finger tip were obtained by lancet to make the
thick smear preparations on the clean, fat free slide glasses. The dried smears
were brought to the laboratory, and microscopic examination of the dried blood
smears were done after staining with Giemsa solution to detect the microfilariae.
The environmental condition survey in the endemic areas was done with a
questionnaire designed by the author. Fifty-three microfilariasis cases(male, 34;
female, 19) and 47 control students(male 30; female, 17) of Namwon Junior High
School were complied with this schedule.
Physical measurement of body length by Martin's anthropometer(Super Co.), body
weight by the portable weight balance, hand grip by Hand Grip Dynamometer(TKK), and
back lift strength by Back Dynamometer(TKK) were examined with the ordinary
All the examinees took a good rest, seated 30 minutes before the test. After the
number of heart beats and blood pressure of the examinees were checked by pulse
meter(Heartpet HR-7A, Mitsubishi Electric Co.) and sphygomomanometer. The examinees
exercised, practicing up and down the wooden box of 30cm height 5 minutes at the
speed of 30 times in a minute. After the loading, the frequency of heart beat was
measured by pulse meter with a minute interval. The increasing pulse and recovery
rate of each test were calculated by the following formula:
Increasing pulse=(Pulse immediately after H.S.T.)/(Resting pulse)×100
H.S.T.: Harvard Step-up Test
Recovery rate=(Step for 5 mins(30×5')×300(30cm.))/(Total pulse at 1's+2's+3)
All the examinees rested in the seat for 30 minutes before blood flow test. In
the resting situation, a sphygmomanometer was fixed on the examinee's thigh to
check the blood flow, and then Whitney's strain gauge for volume estimation of
blood flow(ml/min/100gm tissue) was settled on the lower leg, respectively. All of
the records were indicated on the dynograph(Beckman RS Type) by the perception of
strain gauge plethysmograph.
After measuring the arterial blood flow in succession of venous occlusion(50mmHg)
at the resting period, arterial blood flow was occluded under 200mmHg pressure for
5 minutes. The first check of the arterial blood flow was performed immediately
after reactive hyperemia(0' sec.), sustaining the venous occlusion. Five minutes
after the first check, it was checked at 30 second intervals for 5 minutes and then
continued at one minute interval for next 5 minutes. Up to 10th minute, the values
detected in this test were calculated by the routine formula of blood flow test.
For intelligence test standard questionnaire from which was published at the
Institute of Educational Psychology, College of Education, Seoul National
University was used. Serum protein was measured by rapid electrophoresis using
sepraphore Ⅲ strip. Differential leukocyte count was done routinely Wright stain
of thin blood smears. In the study of bacterial infection blood agar plate and
thioglycollate broth media were used in culture for identification of bacteria.
During the summer season(July-August) 1969, the insecticide tests for resistance
on adults and larvae of Aedes togoi were carried out. Aedes togoi larvae were
collected from the breeding places, tidewater rock pools in endemic area of
filariasis in Cheju-Do, and adults in the test were bred in laboratory from the
larvae. WHO standard method for insecticide resistance test on adults and larvae of
mosquitoes(1963) was applied.
The results were as follows: Eight out of 257 male students of Seogi Agricultural
High School were microfilarial positives(3.1%). the students from Namwon-Myun, one
of the high end endemic focus, revealed the highest prevalence(10.3%), and the
positive cases among these students were the residents mostly in
Wimi-Ri(Ri-village), Namwon-Ri and Taeheung-Ri located along the coastal area in
Namwon-Myun. Out of 724 blood smears in Seogi Girl's High School, only 6(0.8%) were
positive, and all of those were from Bupwhan-Ri, Hokeun-Ri in Seogipo-Up and
Wimi-Ri in Namwon-Myun.
Out of 521 students of Namwon Junior High School, the prevalence of the
microfilariae was 10.9%(male, 12.3%; female, 9.1%). The positive rates were 10.2%
in Taecheung-Ri, 26.8% in Wimi-Ri, 9.4% in Namwon-Ri and 8.2% in Shinheung-Ri, and
all of them were located lining the coastal area; but none of the students who
inhabited the mountainous are showed positive.
The positive rate among 164 children in the fifth and sixth year grade of Wimi
Primary School was 19.5%(male, 16.5%; female, 23.9%). The highest positive
rate(22.8%) was found among the children resided at one out of 6 villages, Wimi-Ri,
where the parasite has been highly prevalent.
As a preliminary check to detect endemic foci of filariasis in a wide area the
rusult of a night blood survey on children and students in school might be valuable
for extensive practical field work on filariasis among general population.
One hundred students of Namwon Junior High School(male, 64; female, 36) were
subjected for the survey by questionnaire. In average, the family members of each
household were 7.1 in the filariasis group(male, 30; female, 17) and 6.6 in the
non-filariasis group(male, 30; female, 17). The numbers of the households in which
the examinees dwelt more than 10 years in Cheju Island were 47(86.8%) in the
filariasis group and 40(85.1%) in the non-filariasis group.
Thirty-three households(62%) of the filariasis group were located within 500
meter area from the coastal line, and 15(31.9%) of the non-filariasis group.
Elephantiasis patients were found in 18(33.9%) out of 53 households of filariasis
students and in 8(17.0%) out of 47 households of the non-infected group.
Fourteen out of 36 students(38.9%) misunderstood that elephantiasis was due to
drink unsuitable water, and the students who gave the right answer about the vector
of the filarial parasite were only 15%.
Height and weight of the body, hand grip and back lift strength of the students
aging 10 to 15 years were measured. The examinees were 80 students in both infected
and non-infected group, respectively. Height and weight in 13 year-old and 15
year-old male students of the infected group showed a slight decrease as compared
with the non-infected group, but no difference was observed in female groups. The
mean values of the hand grip power between two groups were compared. The mean
values of back lift strength in the filariasis students were 63.8kg in 10 year-old
male group and 36.0kg in 11 year-old female group, whereas the values in healthy
were 50.8kg and 44.2kg in the same age group. The hand grip and back lift strength
tended to decrease significantly in the filariasis cases. Some physical
examinations with special reference to Harvard Step-up Test were carried out in the
11 to 17 year-old students. the blood pressure(systolic and diastolic) and pulse
were not different in the infected and non-infected students at the resting state.
The pulse recovery rates after taking exercise by Harvard Step-up Test were
156.5(male) and 152.5(female) in the filariasis cases in contrast to 171.7(male)
and 164.5(female) in non-filariasis group. In the same test, the values of
increasing pulse were 176.8(male) and 179.6(female) in filariasis cases, but
169.2(male) and 161.8(female) in non-filariasis group.
A 69 year-old female elephantiasis case who suffered from cuticular hypertrophy
in right lower leg showed greater delayed recovery of arterial blood flow following
reactive hyperemia in the elephantiasic leg than in the healthy side. In spite of
taking time immediately after reactive hyperemia, the slope of blood flow curves on
the dynograph was more precipitous in the swelling leg that in the control one. In
comparison of blood flow following time in minutes among 7 elephantiasis cases and
6 control healthy, the increased of blood flow immediately after reactive hyperemia
was more significant in healthy group(p-value<0.05), whereas the recovery of blood
flow by time delayed in the elephantiasis group. In the result of intelligence test
for the students of Namwon Junior High School there was no significant difference
between filariasis and healthy group.
In comparison of serum protein of 4 elephantiasis cases and 2 control persons,
measured by rapid electrophoresis, lower gamma-globulin values and higher A/G ratio
were observed in elephantiasis group. Clinical manifestation of 32 elephantiasis
cases aged 13 to 79 yeats were surveyed. The site of cuticular hypertrophy in
elephantiasis cases was 84.4% in the lower extremities and 15.6% in the upper
extremities; however, no case was observed in the upper extremity only.
The symptoms were mainly occasional fever, chilling, headache, pain and lumbago
in decreasing order. Skin injury and hard labour were recognized as the motives for
those symptoms. All elephantiasis cases complained the labour difficulty during the
The range of eosinophilic leukcocytes was 1∼13% in the elephantiasis cases and
1∼10% in the filariasis cases. Bacterial infection at the location accompanied
with acute inflammation was proved in 9 elephantiasis cases. Staphylococcus in 4
cases and Gram negative bacilli in 5 cases were detected.
Insecticide susceptibility tests of both adults and larvae of Aedes togoi were
perform to elucidate preventive measures in the future. The mortality rates of
Aedes togoi larvae were 67.6% in 0.5ppm and 100% in 2.5ppm of DDT., and LC^^50 was
0.085ppm. By BBC LC^^50 was 0.078ppm and by Dieldrin LC^^50 was 0.0075ppm.
The 3 day-old adults of Aedes togoi showed mortality rate of 88.7% in 4% DDT and
LC^^50 was 2.2%.
Summarizing above results:
1. Among 521 students of Namwon Junior High School, the prevalence of the
microfilariae of Brugia malayi detected in the blood smears was 10.9%(male, 12.3%;
female, 9.1%). The positive rates according to the villages of these students'
residence showed 10.2% in Taecheung-Ri and 26.8% in Wimi-Ri which were located
together along the coastal area, but one of the students resided in the mountainous
area showed positive.
2. The positive rate of malayan microfilariae among 164 children, resides at 6
villages, of Wimi Primary School(5th and 6 th year grade) was 19.5%. Highest
rate(22.8%) was found in children resided at Wimi-Ri where has been known as the
high endemic focus of the parasite in Cheju-Do.
3. The students who gave the right answer to the questions regarding the vector
of the filaria were no more than 15%.
4. In comparison of height and weight of the body, hand grip and back life
strength measurements between filariasis and non-filariasis students in this study;
the filariasis group was inferior to the control, especially in hand grip and back
lift strength test.
5. The pulse recovery after taking exercise by Harvard Step-up test delayed more
in the filariasis cases than in the healthy controls.
6. In an elephantiasis case, the normal recovery of blood flow in accordance with
the reactive hyperemia was delayed more in the elephantiasic leg that in the normal
leg. Among 7 elephantiasis cases and 6 healthy persons, the increase of blood flow
immediately after reactive hyperemia was more faster in the healthy group, whereas
the recovery of blood flow by time delayed in the elephantiasis.
7. The intelligence test for the students of Namwon Junior High School showed no
difference between the filariasis and the healthy group.
8. The total serum protein level were increased more in the elephantiasis cases
than in the healthy controls. Albumin-globulin ratio in the elephantiasis patients
was 0.66 in average.
9. the site of cuticular hypertrophy in elephantiasis cases was 84.4% on the
lower extremities and 15.6% on the upper extremities.
10. The principal clinical manifestations were occasional fever, chilling,
headache, muscle pain and lumbar pain in decreasing order.(skin injury and hard
labour were recognized as the motives for those symptoms).
11. Elephantiasis patients complained of working difficulty during clinical
12. Eosinophil leukocytes were 1∼13% in the elephantiasis cases and 1∼10 in the
13. Various microorganisms were detected from the inflammed portion of
14. Both adults and larvae of Aedes togoi showed susceptibility to the
insecticides DDT, Dieldrin and BHC.