Period since Taiwan Restoration - Parasitic Diseases as an Index of Environmental Changes in Tw

First of all, it should be noted that there are two papers which provide general review of parasitic infections in Taiwan at different stage. In 1965, Hsieh Hsien-chen (1924-2000), an eminent parasitologist, presented a paper to discuss soil-transmitted helminthic infections in Taiwan. He collected infection rates obtained by surveys during the Japanese colonial period and Hsieh himself and other scholars in 1956-1963, and showed them on three maps respectively for hookworm (Ad and Na), Ascaris lumbrisoides, and Trichuris trichiura. He also enlisted the rates of Strongyloides stercoralis and Trichostrongylus orientalis. The infection rates of various species differed, however, in the early 1960s the highest rate was still around 80%. Hsieh pointed out that from the viewpoint of public health, hookworm and Ascaris required special attention.⁷⁸

In 2001, Yeh Ta-chuan et al. presented a review for the changing status of parasitic infection in Taiwan since the mid-twentieth century. In brief, malaria was eradicated by 1965 and lymphatic filariasis in the 1980s. The infection rate of soil-transmitted intestinal nematodes among school children was reduced from 70% in the 1950s to 2% in the 1990s. The infection of roundworm, whipworm, and hookworm was under control by the end of the twentieth century, but enterobiasis was still quite popular among school children. Food-borne parasitic zoonosis such as clonorchiasis and taeniasis are confined to some ethnic groups, whereas angiostrongyliasis is associated with the rainy season. The protozonal infections with Giardia lamblia and Cryptosporidium parvum are not rare, but their prevalence is difficult to assess because of lacking epidemiological surveys. Among patients with human immunodeficiency virus (HIV) infections in Taiwan, the leading parasitic pathogens are Pneumocystis carinii, Entamoeba histolytica, and Toxoplasma gondii.

In addition, a relatively common parasitic infection rate among the Southeast Asian workers employed in Taiwan had already caught the attention and a long-term study showed that the overall parasitic infection rate of these workers was 10.3%.⁷⁹

In the second half of the twentieth century, surveys on parasitic infections in Taiwan were mostly conducted among school children, local inhabitants and aborigines. This paper lists the infection rates of 4 helminthes and 3 protozoas in Appendis 3 and 4 in order to observe changes through time and space. Generally, the cases of a same place with surveys at different times are rather rare. For example, at

78 Hsieh Hsien-chen, 1965, “The Incidence and Intensity of Common Soil-transmitted Helminthic Infections in Taiwan,” JFMA, 64:4, pp. 222-238.

79 Yeh Ta-chuan, Lin Pey-ru, Chen Eng-rin, and Shaio Men-fang, 2001, “Current status of human parasitic infections in Taiwan,” Journal of Microbiology, Immunology and Infection, 34:3, pp.

155-160.

Shihpai district in Taipei city (previously belonged to Taipei Prefecture and Taipei County) there were 4 surveys: the first by Yokogawa et al. in 1929-31, the second by Loo in 1939, the third by Huang and Chiu in 1959-1960,⁸⁰ and the fourth by Yu and Chiu in 1975.⁸¹ These four surveys showed that in the case of Al, the infection rates were 98.5%, 87.0%, 65.2%, and 7.4% respectively, apparently in decline. In the case of Ev, the infection rate was usually very small before 1945, however, due to adopting Scotch-tape swab method the rate was 40.7% in 1960 and 55.5% in 1975; an increase on the contrary. This was because pyrantel pamoate (Combantrin) was more effective for expelling roundworm (Al).⁸² In 1980, the infection rates of Al, Tt, and Hw among school children at five districts in Taipei City had decline to 2.3%, 1.8% amd 0.05%

respectively; reflecting the effect of parasitic controlling since 1972; but this report did not include pinworm.⁸³ Because most of the places only had one survey, it is perhaps better to put together surveys of different places in the same county to try to observe changes through time. This will be showed below.

1. Taipei County

In July-August, 1949, Huang Wen-hsien et al. conducted survey at 4 villages of aborigines at Wulai (Urai烏來) area. There were 634 persons, 84% of the total populations at the 4 villages, received stool examinations.⁸⁴ In October 1954, Jolliffe and Tung investigated the parasitic infections among school children in Taipei area in order to study nutritional conditions. Those received examinations in Taipei County were 219 children from Luchou 蘆洲, 204 from Yingko 鶯歌 and 105 from Hsinchuang 新莊, the original paper pronounced it as Heng-Zing, judging from place names in Taipei County, Hsinchuang is perhaps the best guess), as well as 98 children from Naihu 內湖 in today’s Taipei City.⁸⁵ In 1961, Kuntz et al. presented a paper on surveys covering 7 locations in 5 counties, and among the examinees were 256 inhabitants from Shihmen district 石門鄉. However, the time of the survey was not clearly stated in the paper and the best guess was around 1960.⁸⁶

80 Huang Wen-hsien and Chiu Jui-kuang, 1961, “Resurvey of the Incidence of Intestinal Helminthic Infections among School Children in a Rural Area in Northern Taiwan,” JFMA, 60:2, pp. 216-226.

81 Yu Jen-chieh and Chiu Jui-kuang, 1976, “Present Status of Intestinal Parasitic Infections among Shih-pai Primary School Children in Taipei, Taiwan, with an Evaluation of Pyrantel Pamoate in Treatment,” JFMA, 75: 11, pp. 639-646.

82 Yu Jen-chieh and Chiu Jui-kuang, 1976, p. 644.

83 Wei Teng-hsien, Li Chung-hsiang, Wu Kang-wen, Huang Ching-feng, and Chan Tien-sheng, 1981,

“A Report on Parasitic Control at Five Districts in Taipei City in 1980,” Public Health (《公共衛生》), 8: 1, pp. 107-113.

84 Huang Wen-shien, Loo Wan-teh, Hsieh Hsien-chen, and Wu Chen-lan, 1952, “Parasitological Investigations on the Aborigines in Taipei Prefecture, Formosa,” JFMA, 51: 3, pp. 96-118.

85 Norman Jolliffe and Ta-cheng Tung, 1956, “Nutrition Status survey of the Civilian Population of Formosa,” Metabolism, 5, p. 319, Table 7.

86 Robert E. Kuntz, James C. Burke, S. Lin and Raymond H. Watten, 1961, “Protozoan and Helminth Parasites in Peoples of Taiwan,” JFMA, 60: 9, pp. 809-824.

Table 19 lists the helminthic infections rates found in Taipei County. During 1949-1960, the total helminthic infection rates were 73-96%, with that among the inhabitants in Wulai area ranked the highest. In 1949, the infection rates at Wulai were in the order of Al 81.7%, Hw 66.1%, Tt 63.4%, Tsa 20.5%, and To, Ss and Ev below 1%. In 1954, the infection rates among children at Luchou were in the order of Al 74.9%, Tt 68.5%, Hw 46.6%, and Ev 0.9%; at Yingko, the rates were Al 59.8%, Tt 25.5%, Hw 18.6%, and Ev 0.5%; and at Hsinchuang, the rates were Hw 50.5%, Al 43.8%, Tt 4.8%, and Ev 1.9%. Around 1960, the infection rates among the Shihmen inhabitants were Hw 79%, Al 59%, Tt 29%, Pw 6% and Ev 1%. It is notable that the infection rate of pinworm was mostly around 1% in the above surveys, however, using the Scotch-tape swab method, the Ev infection rate in 1957 was 62.3% at Shengken 深坑 and 72.4% at Chingmei 景美 and 54.3% at Mucha 木柵, the last two places were still belonging to Taipei County at that time.⁸⁷ In 1985, the rate among school children at Juifang 瑞芳 was 33.9%.⁸⁸

Table 19: The Infections of Helminthes among Inhabitants and School Children in Taipei County, 1949-1960 (% in Parenthesis)

Place Wulai Luchou Yingko Hsinchuang Shihmen

Examinee Inhabitants S children S children S children Inhabitants

Time 1949/7-8 1954/10 1954/10 1954/10 1960

No. Examined 634 219 204 105 256

No. Infected 608(95.9) 209(95.4) 148(72.6) 77(73.3) (94)

Al (Ascaris lumbricoide) 518(81.7) 164(74.8) 122(59.8) 46(43.8) (51)

Hw (hookworm) 419(66.1) 102(46.6) 38(18.6) 53(50.5) (79)

Tt (Trichuris trichiura) 402(63.4) 150(68.5) 52(25.5) 5(4.8) (29)

Ev (Enterobius vermicularis) 2(0.3) 2(0.5) 1(0.5) 2(1.9) (1)

To (Trichostrongylus orientalis) 4(0.6) -- -- -- --

Ss (Strongyloides stercoralis) 4(0.6) -- -- -- --

Pw (Paragonimus westermani) -- -- -- -- (6)

Tsa (Taenia saginata) 130(20.5) -- -- -- --

Source：Huang Wen-hsien, Loo Wan-teh, Hsieh Hsien-chen, and Wu Chen-lan, 1952, p. 99, Table 1; p.

101, Table 2. Norman Jolliffe and Tung Ta-cheng, 1956, p. 319, Table 7. Robert E. Kuntz, James C.

Burke, S. Lin and Raymond H. Watten, 1961, p. 815, Table 1

As for the infections of protozoa, the data were available in surveys of 1949 and 1960. At Wulai area, the infections were in the order of Ec 19.4%, Trico 8.5%, Eh 5.7%, En 4.1%, Gl 2.2%, Bc 0.8%, and Ib 0.6%.⁸⁹ At Shihmen, the rates were Gl 10%, Ec and En 9% each, and Eh 3%.⁹⁰ The multiple infections were also found at

87 Lin Yuan-tang, 1962, “Observations on Enterobiasis, I. Observation on Enterobius vermiculoris infection among school children of Chin-mei, Sheng-ken and Mu-cha primary schools in Taipei county, Taiwan,” JFMA, 61: 2, p. 155, Table 1.

88 Chung W.C., Lu J. L. and Chang K. C., 1986, “Survey of Enterobius and Head Louse Infection among Children of Jui-fang Primary School, Jui-fang district, Taipei County,” Journal of Taipei Medical College (《北醫學報》), 15, p. 139, Table 2.

89 Huang Wen-hsien, Loo Wan-teh, Hsieh Hsien-chen, and Wu Chen-lan, 1952, p. 101, Table 2.

90 Robert E. Kuntz, James C. Burke, S. Lin and Raymond H. Watten, 1961, p. 815, Table 1.

Wulai area; there were 11.0% single infection, 25.4% double infections, 33.1% triple infections, 18.4% quadruple infections and 7.6% quintuple infections.⁹¹

2. Hsinchu County

The parasitic surveys in Hsinchu County were mostly conducted at the mountain area. In 1968-1969, Chung Wen-cheng et al. conducted survey at Wufeng district 五峯鄉 and focused on Taenia Saginata. Among 302 persons received examinations, 111 (36.8%) were found infected; the infection rate increased with age and reached the highest 64.7% at ages 31-40.⁹² From July to October 1967, Wen Yung-fu conducted stool examinations with inhabitants at low mountain area at 3 villages in Chienshih district 尖石鄉. There were 239 aborigines and 224 Han Taiwanese received stool examinations; 417 aborigines and 262 Han Taiwanese received intradermal test for lung worm; and 221 aboriginal children and 163 Han Taiwanese children received Scotch-tape swab examination for pinworm.⁹³ In 1978-1979, Wu Yu-yeh and Lü Sen-chi conducted examinations with 346 students at Chienshih Middle School and 600 children at Chienshih Elementary School.⁹⁴ In July 197, Chang Kok-chung et al. conducted survey at Yufeng 玉峯 and Hsiuluan 秀巒 villages at the remote mountain area in Chienshih district with 481 Atayal aborigines.⁹⁵ And from March to July 1979, Chung Wen-cheng et al. also conducted survey at the same two villages with 770 aborigines.⁹⁶

Table 20 shows that in the lower mountain area of Chienshih district, the total helminthic infection rate among the aborigines was 96.2%, with the order of Al 82.4%, Tt 68.9%, Hw 22.2%, Tae 7.2%, Pw 4.3%, and Ev 17.7% among children; the total helminthic infection rate among Han Taiwanese was 88.0%, with Al 79.5%, Tt 56.3%, Hw 17.9%, and Ev 61.4% among children. In 1978-79, the middle school students had a total helminthic infection rate of 75.7%, with various species ranked in the order of Tt 59.5%, Al 43.1%, Hw 4.9%, Tae 2.0%; the total protozoan infection rate was

91 Huang Wen-hsien, Loo Wan-teh, Hsieh Hsien-chen, and Wu Chen-lan, 1952, p. 103, Table 3.

92 Chung Wen-cheng and Liu Jui-chung, 1971, “Survey and Treatment of Taenia Saginata with Atabrine in Aborigines in Wufeng District, Hsinchu County, Taiwan,” Chinese Journal of Microbiology, 4, p. 46. Tables I and II.

93 Wen Yung-fu, 1969, “A Survey on Helminthic Infections among Aborigines in Chien-shih district of Hsin-chu County, Taiwan,” JFMA, 68: 9, pp. 445-450. See p. 446, Table 1.

94 Wu Y. Y. and Lü S. C., 1979, “A Survey on protozoan and helminthic infections among middle and primary school children at Chien-shih district, Hsin-chu county, Taiwan,” Chinese Journal of Microbiology, 12:1, p. 113.

95 Chang Kok-chung, Sun Yun-lai, and Chiu Jui-kuang, 1973, “A Survey on Parasitic Infections among Aborigines in Remote Mountain Area of Chien-shih District, Hsinchu County, Taiwan,” JFMA, 72:5, p. 299, Table 2; p. 301, Table 4.

96 Chung W. C., Fan P. C. and Chiu H. M., 1985, “Survey of Helminthic Infections and Treatment of Taenia Species Infection among the Aborigines in Chien-shih District, Hsin-chu County, Northern Taiwan,” Chinese Journal of Microbiological Immunology (《中華微免雜誌》), 18, p. 96 and p. 98, Table 1.

16.8%, with the order of Gl 10.1%, Ec 4.3%, Eh 1.4%, and En 0.6%. The elementary school children had a total helminthic infection rate of 81.0%, with Tt 75.5%, Al 37.3%, Hw 11.3%, Tae 1.2%, and Pw and Cs 0.02% each; the total protozoan infection rate among children was 18.2%, with Gl 12.3%, Ec 5.5%, Eh 1.7%, and En 0.02%. In addition, the Ev infection rate of children was 47.3%.

Table 20: The Parasitic Infections among Inhabitants and Students at Chienshih Rural Township in Hsinchu County, 1967-1979 (% in Parenthesis)

Place Yihsing, Chialo, Chinping Middle

School Tt (Trichuris trichiura) 164(68.9) 126(56.3) (59.5) (75.5) 189(39.3) 222(28.8)

Hw (hookworm) 53(22.2) 40(17.9) (4.9) (11.3) 13(2.7) 1(0.3)

* Examination with Scotch- Ascaris lumbricoides tape perianal swab method.

Source: Wen Yung-fu, 1969, p. 446, Table 1. Wu Y. Y. and Lü S. C., 1979, p. 113. Chang Kok-chung, Sun Yun-lai, and Chiu Jui-kuang, 1973, p. 299, Table 2; p. 301, Table 4. Chung W. C., Fan P. C., Chiu H. M., 1985, p. 98, Table 1.

In the remote mountain area of Chienshih district, the total helminthic infection rate was 93.1% in 1971, with Al 88.8%, Tt 39.3%, Tsa 9.4%, Hw 2.7%, Hd 0.8%, and Echinostoma sp. (Ech) 0.6%. The total protozoan infection rate was 28.5%, with Ec 15.4%, Gl 8.5%, Eh 7.5%, En 3.1%, Ib 0.6%, Bc 0.4%, and Cm 0.2%. In 1979, The total helminthic infection rate was 80.0%, with Al 77.1%, Tt 28.8%, Tsa 18.4%, Ev 1.6%, and Hw, Hn and Hd each had 0.1%.

Compared the results of two surveys each in the lower and remote mountain areas of Chienshih district, it is notable that in 1979 the helminthic infection rate was still rather high but was already lower that in 1967-1971. This was related to the

parasitic controlling program initiated in 1972 by the government.⁹⁷

It should be noted here that in 2001, Fan Ping-chin et al reported that the tapeworm found in Taiwan was different from classical Taenia saginata and it was given a new name of Taenia saginata asiatica in 1995. They summarized the results of examinations conducted during 1971-1992 with 27,359 at 88 villages of 14 mountain districts in 10 counties and counted 3,104 persons (11% of the total) were infected with this parasite. Counted by each county, Taipei had 62 persons (8%), Taoyuan had 212 persons (10%), Hsinchu had 467 persons (12%), Yilan had 1,298 persons (16%), Nantou had 310 persons (6%), Chiayi had 3 persons (0.4%), Kaohsiung had 56 persons (9%), Pintung had 10 persons (4%), Taitung had 319 persons (11%), Hualien had 367 persons (13%).⁹⁸ It is notable that the infection of Taenia saginata asiatica in Hsinchu was only lower than that in Yilan and Hualien counties.

3. Yilan County

Regarding the parasitic infections among inhabitants in Yilan County, the earlier surveys focused on school children at Kuishan Island 龜山島. There are three reports: Kuntzs and Wells examined 80 children in 1959-62;⁹⁹ Chung and Cross examined 158 children in 1975;¹⁰⁰ and Chung Wen-cheng examined 62 children in 1977.¹⁰¹ In addition to Kuishan Island, Kuntz and wells also examined 204 children and 115 adults at Toucheng 頭城, 147 Taiwanese children and 116 aboriginal children at Nanao 南澳. In 1978-1979, Fan Ping-chin’s team adopted Formalin-ether concentration method to examine intestinal parasites with 1,767 students at four middle schools at Chuangwei 壯圍, Toucheng, Yuanshan 員山 and Chiaohsi 礁溪, and used the Scotch-tape perianal swab method to examine pinworm with 2,329 children.¹⁰² In January and February 1980, Fan Ping-chin’ team used the same methods to examine 1,074 students at Nanao for intestinal parasites, and 1,051

97 Chung W. C., Fan P. C. and Chiu H. M., 1985, p. 99.

98 Fan Ping-chin, Chung Wen-cheng, and Chen Eng-rin, 2001, “Parasitic Infections among the Aborigines in Taiwan with Special Emphasis on Taeniasis Asiatica,” Kaohsiung Journal of Medical Science, 17: 1, p. 2, p. 7, Table 4.

99 Robert E. Kuntz and William H. Wells, 1967, “Parasites in School Children of I-lan and Peng-hu Hsiens; and Adults in I-lan and Chang-hua Hsiens, Taiwan,” JFMA, 66: 6, pp. 300-307.

100 Chung Pyung-rim and John H. Cross, 1975, “Prevalence of Intestinal parasites in Children on a Taiwan Offshore Island Determined by the Use of Several Diagnostic Methods,” JFMA, 74:6, pp.

411-418.

101 Chung Wen-cheng, 1977, “ Report on Survey on Parasitic Infection at Kuishan Island, Yilan County, Taiwan,” Biological Science (《生物科學》), 11, pp. 47-54.

102 Fan P. C., David Chao, Liu H. Y., Lee K. M., Cheng F. Y. Wang K. H. and Lee S. H., 1980,

“Comparative Studies on Prevalence of Common Intestinal Nematode Parasites in the Tape-water and Non-tape-water Supported Areas in Taiwan, Part I. Prevalence and Chemotherapy of Common Intestinal Nematode Parasites among Junior High School Students in Ilan County, Northern Taiwan,” National Science Council Monthly (《科學發展月刊》), 8: 12, pp. 1168-1179.

children at Nanao and 200 children at Chuangwei for pinworm.¹⁰³ From April 1981 to March 1983, Fan Ping-chin’s team conducted survey and treatment of parasites at Nanao and Tatung 大同 districts.¹⁰⁴

Table 21.1: The Parasitic Infections among School Children at Kuishan Island, Yilan County, 1959-1977 (% in Parenthesis)

Helminth

Year 1959-62 1975 1977

No. Examined 80 158 62

Al (Ascaris lumbricoides) (93) 76(48) (41.9)

Tt (Trichuris trichiura) (100) 157(99) (75.8)

Hw (hookworm) (0) 22(14) (25.8)

Ev (Enterobius vermicularis) (1) 20(13) (16.3)

Ev (Enterobius vermicularis)* -- -- (58.3)*

Hn (Hymenolepis nana) (4) 30(19) (11.3)

Hd (Hymenolepis diminuta) (0) (0) (3.2)

Tae (Taenia saginata) (1) (0) (1.6)

Didymozoon-like egg (41)

Protozoa

Year 1959-62 1975 1977

No. Examined 80 158 62

Eh (Entamoeba histolytica) (23) 29(18) (4.8)

Eha (Entamoeba hartmanni) (15) 28(18) (14.5)

Ec (Entamoeba coli) (30) 62(39) (46.8)

En (Endolimax nana) (9) 23(15) (8.1)

Df (Dientamoeba fragile) (3) 5(3) (0)

Ib (Iodamoeba bütschlii) (0) 4(3) (0)

Cm (Chilomastix mesnili) (5) (0) (1.6)

Gl (Giardia lamblia) (9) 50(32) (30.7)

Tricho (Trichomonas hominis) (0) 32(20) (1.6)

Enba (Enbadomonas intestinali) (0) (0) (1.6)

Bc (Balantidium coli) (0) (0) (1.6)

Isospora (0) 1(0.6) (0)

* Examination with Scotch-tape perianal swab method. The number examined was 132.

Source: R. E. Kuntz and W. H. Wells, 1967, p. 304, Table 1. Chung Pyung-rim and John H. Cross, 1975, p. 415, Table 4. Chung Wen-cheng, 1977, p. 50, Table 1; p.53, Table 5.

103 Fan P. C., David Chao, Liu H. Y., Lee K. M., Cheng F. Y. Wang K. H. and Wu C. C., 1981,

“Comparative Studies on Prevalence of Common Intestinal Nematode Parasites in the Tape-water and Non-tape-water Supported Areas in Taiwan, Part II. Prevalence of Common Intestinal Parasites among Children in the Remote Area of Taiwan and Determination of the Minimum Effective Dose of New Broad Spectrum Anthelmintics against the Common Intestinal Parasites,” National Science Council Monthly (《科學發展月刊》), 9:2, pp. 159-175.

104 Fan P. C., Chung W. C., Chan C. H., Lee K. M., Wang C. C. and Wu C. C. , 1982, “A Pilot Control Study of Common Intestinal Parasites and Head Louse among Aboriginal Children in Taiwan, ROC, Part I. Prevalence and Chemotherapy of Parasitic Infections among Aboriginal Children in Nan-ao and Ta-tung districts, Ilan County, Northern Taiwan,” National Science Council Monthly (《科學發 展月刊》), 10: 9, pp. 773-798；Fan P. C., Chung W. C., Chan C. H., Cheng F. Y., Chen Y. A., and Hsu, M. C., 1984, “A Pilot Control Study of Common Intestinal Parasites and Head Louse among Aboriginal Children in Taiwan, ROC, Part II. The 2^nd Year Survey and Treatment of Intestinal Helminths and Head Louse Infections among Aboriginal Children in Ta-tung and Nan-ao districts, Ilan county, Northern Taiwan,” National Science Council Monthly (《科學發展月刊》), 11: 12-3, pp.

1511-1535.

Table 21.1 shows that during 1960-1977, the parasitic infections among school children at Kuishan Island had changed substantially; the rate of Al declined from 93% to 41.9%; that of Tt from 100% to 75.8%; but that of Hw increased from 0 to 25.8% and that of Ev from 1% to 16.3%; using the Scotch-tape swab method the infection rate of Ev in 1977 was 58.3%. Of the protozoa, the rate of Eh declined from 23% to 4.8%, but that of Eha and En declined only slightly; on the contrary, the infection rates of Ec and Gl increased a lot; Ec from 30% to 46.8% and Gl from 9% to 31%. For other species, the infection rate was mostly around 1% or none at all.

Moreover, the survey in 1975 discovered 41% infected with Didymozoon-like egg.

Table 21.2 shows that around 1960, the total helminthic infection rate among students at Toucheng middle school was 98% and among the adults 90%. Specifically, both the students and adults had 70% infected with Al and 68% with Tt; but the students had 25% infected with Hw while the adults 36%; the students had 1%

infected with tapeworm and the adults 2%. At Nanao, both the aboriginal and Han Taiwanese children had 100% infected with parasites; with Al 93% and 99%

respectively, Tt both 90%, Hw 29% and 50% respectively; showing higher rates among the aborigines. In addition, the aborigines had 13% infected with tapeworm. In 1978-1979, the total infection rate among students in Yilan was 42%, with Al 14.5%, Tt 32.9%, and Hw 3.9%; much lower than those rates in 1960. However, using the Scotch-tape swab method, the infection of Ev was 41.9%; much higher than 9% with other method. It is also notable that the surveys in 1978-79 found that the parasitic infection rates were not closely related with the supply of tape-water.¹⁰⁵ In February 1980, the survey at Nanao found that the total infection rate was 60.9%, with Tt 45.3%, Al 39.9%, Hw 10.6%, Tae 2.4%, and Hn 0.5%. Using the Scotch-tape swab method, the results showed the positive rate was 25% among 1,051 children at Nanao and 49% among 200 children at Chuangwei; demonstrating that enterobiasis was more prevalent among children at the plain than at the mountain area.¹⁰⁶

As for surveys conducted at Nanao and Tatung districts during 1981-1983, Table 21.1 listed the results before treatment (1981/5), after the first treatment (1982/6) and after the fourth treatment (1983/1). In the case of Nanao, the total infection rate declined from 79% to 24%, with Al from 53% to 0.6%, Tt from 57% to 21%, Hw from 16% to 0, and Ev from 4% to 1.2%. In the case of Tatung, the total infection rate declined from 83% to 25%, with Al from 64% to 1.5%, Tt from 66% to 24%, Hw from 7% to 0.3%, and Ev from 8% to 1.8%. The magnitude of decline was quite substantial. Moreover, the result of using the Scotch-tape swab method to examine

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