IV. AN EPIDEMIOLOGIC SURVEY IN YAMANASHI PREFECTURE, HONSHU, JAPAN INTRODUCTION

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1 kj.m.j., Vol. 4, No. 2 April, 1951 l PARASITOLOGICAL STUDIES IN THE FAR EAST. IV. AN EPIDEMIOLOGIC SURVEY IN YAMANASHI PREFECTURE, HONSHU, JAPAN BY G. W. HUNTER III1,2, L. S. RITCHIE1, E. H. KAUFMAN1,3, C. PAN1, M. YOKOGAWA4, N. ISHII4 AND J. T. SZEWCZAK1 WITH THE TECHNICAL ASSISTANCE OF R. E. WEBER1, S. ASAKURA1, Y. HISHINUMA1 AND F. WILLIAMS, JR.1 INTRODUCTION This parasitological survey was undertaken in Yamanashi Prefecture during December 1947 and was completed by the end of February As in the case of the preceding surveys it was a cooperative undertaking with the Japanese National Institute of Health. The principal objectives included a determination of (i) the incidence, (ii) the density of the infections in the various communities, (iii) the epidemiologic factors predisposing to infection and (iv) an intensive study of schistosomiasis, as neither the incidence nor parasite density was accurately known. METHODS Representative population centers for the various types of agricultural pursuits occurring in Yamanashi were selected at random in these categories : cultivation of mulberry, vineyards, and valley or hillside rice paddies. No prior knowledge of the extent of parasitism was known other than that schistosomiasis existed in some of the communities. A sixth center, the Pref ectural capital, was added to secure a typical urban population. Approximately 500 stools were obtained from a representative cross section of the population in each of these six communities. Each individual was given a physical examination. Stools were examined by the AMS III (1) 1. Department of Medical Zoology, 406th Medical General Laboratory, APO 500, San Francisco, California. 2. Colonel, MSC, US Army, Chief of Department. 3. Captain, MC, US Army. 4. Department of Parasitology, National Institute of Health, Tokyo, Japan. 113

2 114 HUNTER et al and MGL (2) techniques for helminths and protozoa; direct smears were made on about 10% for comparison. Scotch tape swabs were taken on most of the children for the recovery of pinworn eggs. Blood specimens for malaria and filariasis were not taken, since these diseases were not endemic. A discussion of the general plan and techniques occurs in the initial paper of this series (3). PHYSICAL AND CLIMATOLOGIC DATA FOR YAMANASHI PREFECTURE Six population centers, consisting of Kofu City and five nearby villages were surveyed. The principal crops in these rural communities were:, Kissawa - rice and other grains (on terraced hillside) Otsuka - mulberry (on hillside) and rice (in valley) Hikawa - vineyards, some mulberry, and dry farming (in the valley) Futakawa - rice and other grains (in valley) Sancho - rice and other grains (in valley) In addition to the above mentioned crops each household invariably planted a vegetable garden which usually included some sweet potatoes. One unusually interesting fact was discovered at Kissawa, where the fields were mostly situated on a rock-terraced hillside with an eastern slope. The chief crops cultivated were : rice grown in paddies, wheat and barley; the last two being secondary winter or spring crops. Irrigation water for the upper hillside paddies was brought from the adjacent Mutsusawn valley. A large thriving colony of Oncomelania nosophora existed along the course of the main irrigation channel on the Mutsusawa hillside; the snails in the Kissawa valley were limited to the terraces irrigated with Mutsusawa water, and undoubtedly had their origin in the Mutsusawa colony. The records of temperature, rainfall humidity and evaporation were secured from the Kofu meteorological station. The monthly temperature averages were quite similar to those of Fukui, and the annual average of 13.4 Ž was identical. The four winter months averaged well under 10 Ž which is supposed to be the minimum at which hookworm eggs and larvae develop. Only in July and August did the monthly averages reach the figure of 25 Ž which is optimal for the development of hookworm. The rainfall of 1258 mm. was slightly less than for Aomori, and was approximately half that of Fukui. The soil types! occuring in the localities surveyed are:(i) Kissawa - Unpublished Data, Natural Resources Section, GHQ, SCAT.

3 PARASITOLOGICAL STUDIES IV115 a 12 inch surface of heavy silt loam under which there is a very heavy 30 inch layer of clay; (ii) Kofu City - a silt loam clay in the northern part and a sandy loam in the southern portion; (iii) Hikawa - a very sandy soil apparently produced in part by flooding; (iv) Futakawa - also sandy; (v) Sancho - loam to silt loam; and (vi) Otsuka - silt loam in the valleys and silt loam or volcanic ash on the hills. Most of the soils were poorly drained except for the hillside at Otsuka and parts of Kof u City; most of them were gstrongly acid hranging in ph from 5.0 to 5.5. EPIDEMIOLOGIC DATA FROM YAMANASHI PREFECTURE Previous Data on Incidence of Intestinal Parasites.- Previous records concerning parasitism in Yamanashi dealt only with the incidence of helminthiasis from 1922 to 1927 and revealed: Ascaris lumbricoides 80.3%, Trichuris trichiura 73.7%, hookworm 30.3% and Trichostrong ylus sp. 1.8% (3). This report also noted that 6.8% of the population of Yamanashi were infected with Schistosoma japonicum. wright et al (4) examined school children from four selected villages and found A. lumbricoides in 80.8%, T. trichiura in 32.3%, hookworm in 27.1% and S. japonicum in 53.5%. Summary and Discussion of Incidence Data for the Survey as a Whole.- One or more species of intestinal parasites were found in 99.5% of the 3,055 persons examined. (See Table I). Helminths alone accounted for an incidence of 99.4%, while 53.9% were infected with protozoa (5). A total of 12,994 parasitic infections were harbored by the 3,055 individuals examined, an average of 4.25 per person. Corresponding figures for helminths alone were 10,403 infections, or 3.41 per person, and in the case of protozoa the average was 0.85 infections. There were four individuals infected with nine parasites each, 34 were infected with eight, and 723 persons had five each. These striking figures are based principally on the following five helminths which occurred with greatest frequency: A. lumbricoides, T. trichiura, hookworm, Trichostrongylus sp. and S. japonicum; and the more commonly found protozoa: Endamoeba histolytica, E. coli and Endolimax nana. Whereas five helminths occurred with a high incidence in Yamanashi, only two occurred with equivalent frequency in Fukui and three in Aomori Prefectures (6, 7). Trichuris trichiura was the most prevalent parasite with an incidence of 91.6% as compared to A. lumbricoides which had only 88.8%. Hookworm occurred in 71.8% of those examined while Trichostrongylus sp. was present in 44.4%. Schistosoma japonicum was found in 32.0% of the 3,055 who were examined. This figure includes non-endemic as well as endemic centers. Pinworm, Enterobius vermicularis, was found in 36.9% of the 723 children who were examined by means of the scotch tape swab.

4 116HUNTER et al Other helminths found less frequently included fifteen cases of Clonorthis sinensis, five cases of Metagonirnus yokogawai, two cases of Echinochasmus perf oliatus and one case each of Hymenolepis nana, Paragonimus westermani and Strongyloides stercoralis. Sixty-nine cases of unidentified heterophyid-like eggs were found, but many of these were apparently spurious infections due to the ingestion of uneviscerated fish. Among the intestinal protozoa there was an incidence of 10.3% for Endamoeba histolytica. The corresponding figures for the other protozoa were: E. coli 42.9%; Endolimax nana 22.0%; Iodamoeba biutschlii 2.5%; Giardia lamblia 5.0% and Chilomastix mesnili 2.3%. For the surveys in Fukui and Aomori Prefectures the incidence of E. histolytica was 11.3% and 7.4% respectively. Comparison o f Parasitism in the Various Communities Surveyed.- Ninety-nine percent (99%) of the people in each of the six population centers surveyed harbored one or more parasites. The occurrence of helminthiasis likewise was 99% for each village, but protozoa collectively varied from 44.1% at Otsuka to 62.8% at Hikawa, and for whipworm a high of 96.2% occurred at Kissawa and a low of 86.6% at Sancho. The incidence of ascaris and whipworm in the urban population of Kofu was essentially equal to that in rural communities. Also, it is clearly evident that the occurrence of ascaris and whipworm in Yamanashi is not affected by variations in the principal crops raised, such as rice, mulberry and grapes. Hookworm was lowest in Kofu City, but even in this distinctly urban center the incidence was 59.5%. The highest findings occurred in the rice-growing areas of Sancho and Futakawa where 79.5% and 81.3% respectively were infected. At Otsuka, where mulberry cultivation prevailed, the incidence was 64.3%; in the vineyard area at Hikawa 73.4% were infected, and at Kissawa where rice and grains were raised on terraced hillside paddies the incidence was 72.7%. There was, then, no marked difference in the prevalence of hookworm for mulberry, grape and rice culture; neither was there any significant difference in the parasite density index. Cort et al (8), also Chang and Tong (9) noted in China that hookworm was less prevalent in strictly rice-growing areas. Further, Cort et al (10) observed in the mulberry district of the Yangtze delta, in eastern China, that practices of applying night soil and picking leaves from lowtrimmed bushes resulted in a high incidence of hookworm. On the other hand, Chang, Tong et al (11) found, in the mulberry district of the western province of Szechwan, that the incidence was relatively low, due to different practices of cultivation, fertilization and leaf-picking. In anticipating the epidemiologic factors which account for hookworm in Yamanashi Prefec-

5 PARASITOLOGICAL STUDIES IV117 ture, it appears at least in part that they represent a common denominator for all the population centers surveyed, including Kofu City. It seems that the universal use of night soil in the dooryard gardens constitutes such a factor. This would explain the high incidence in the urban population, as dooryard gardens are frequent there, except perhaps in the heart of the city. Such gardens may be particularly critical because of their proximity to the toilet and fresh night soil. Where all the land is suitable for wet rice, summer gardens are largely limited to those of the dooryards; however fall and spring gardens, and wheat, barley or rape seed are planted as interim crops, and are fertilized with night soil. Chang and Tong (9) noted that a relatively high incidence of moderate hookworm infection occurred in a truck-gardening section of Szechwan. Tang (12) and Chang (13) noted respectively in Fukien and Szechwan, China, that people connected with the planting and cultivation of sweet potatoes were apt to have a high incidence of severe hookworm infection. Sweet potatoes are quite a staple crop in Yamanashi, as they are in most rural communities of Japan. It appears, therefore, that the incidence of hookworm is tied up with gdry farming hthat occurs so universally during a part of the growing season in this area. Schistosoma japonicum was found to occur in about 65% of the people in two of the six villages surveyed, approximately 30% of two others, and less, than 5% of the remaining two, the findings being as follows: Sancho and Futakawa, 65.9% and 64.6% respectively; 30.0% and 27.4% for Kissawa and Otsuka ; and 3.4% and 0.2% for Kofu City and Hikawa. Only Sancho, of the above six villages was surveyed by Wright et al (4), for which they reported an incidence of 61.3% for school children. The actual status of schistosomiasis may be more nearly reflected by figures obtained by us in a more recent investigation (1950). Approximately 200 children, 11 to 15 years old, in each of six communities were all examined six times for helminths by means of the ANTS III technique (1). In three of these, Shiozaki, Mikage and Tamahata, over 90% of the children were found to be infected, and in two others the incidence was between 80% and 90%. In this connection it should be noted that the infections of schistosomiasis in the age groups above 15 years are essentially equal to those of the 11 to 15 year category. The.occurrence of protozoa, collectively, was lowest in the rice growing villages. of Sancho and Futakawa, highest at Otsuka and Hikawa, and intermediate at Kissawa and Kofu a City. The two highest figures, in comparison with the two lowest, represent a highly significant difference; also

6 118HUNTER et al the highest and lowest, in comparison with the intermediate figure, give significant differences as based on the Chi-squared test. General conditions of living and sanitation are relatively uniform for all the communities; the fly population is dense everywhere, and there would not be much, if any, difference in the personal sanitation of family food handlers from one community to the next. Certain observations can, however, be made regarding the possibility of water accounting for some of the above differences. At Hikawa the entire area had been flooded just a few months prior to this survey. The inundation was general and severe enough to flood the open wells and night soil receptacles. Such a circumstance could account for the relatively high incidence of intestinal protozoa which occurred there. At Otsuka, gardens and fields extended well above the level of this hillside village. At times of heavy rain, polluted run-off water from cultivated areas would flow through the village streams. Furthermore, many of the open wells of this village were so poorly constructed that run-off water from the dooryard slopes and adjacent gardens could readily enter them at times of heavy rains. Kissawa was somewhat comparable to Otsuka, except that in Kissawa more of the dwellings were on the floor of the narrow valley. In contrast to the above, Sancho and Futakawa, with a low incidence of protozoa, were entirely situated on the bottom of the Kofu valley. Severity of Helminth Infections.- The incidence of the various parasites reported here is based upon the examination of approximately two grams of feces. The numbers of eggs are counted and recorded as previously described (3) in gplus hcategories. These in turn form the basis for the parasite density index. This index furnishes evidence of the intensity of infections with ascaris, whipworm, hookworm and others. The parasite density index has been correlated with the Stoll Dilution Egg Count so that interpolations can be made if desired. In Yamanashi Prefecture, A. lumbricoides had a parasite density index of 126. The variation in the different communities was marked (Table II), ranging from 84 in Kofu City to 191 in Sancho. This correlates well with the epidemiologic picture, as it is expected that those persons living in a city such as Kofu would be exposed less frequently to ascaris than the farmer in a community like Sancho. Similar variations will be found in the case of the other helminths which are recorded in detail in Table II.

7 PARASITOLOGICAL STUDIES IV119 The overall parasite density index for hookworm was 53, and the range of this figure for the several communities was from 41 (Otsuka) to 60 (Sancho and Kissawa). As previously determined (2), the Stoll Dilution Egg Count Equivalents for our gplus hcategories ( }...5+) are respectively 304, 919, 2554, 2705, 8073 and 8745 eggs per gram of feces. Since the ratio of Necator americanus and Ancylostoma duodenale is not known for Yamanashi, it is inadvisable to interpolate worm burden, but rather to arrive at an evaluation of infection severity on the basis of egg counts, after the suggestion of Cort, Stoll and Grant (14). As the result of the studies of these investigators, it is possible to associate egg counts of varying magnitude with proportionate degree of anemia, regardless of the ratio of the two hookworms. They recognized the following egg count categories in relation to varying degrees of anemia: I. Negative to Dilution Egg Count. II. Egg Counts eggs per gram-blood loss compensated. Includes, essentially our }(304) and+ (919) categories. III. Egg Count from eggs per gram-blood loss nearly compensated. Includes our 2+(2554) and 3+(2705) categories. IV. Egg Count from disturbance or break in compensation. Includes our 4+(8073) and 5+ (8745) categories. V. Egg Count of 10,000 and over-severe hookworm disease. All such cases in our survey are averaged into the higher gplus h categories, which are limited to group IV. The Stoll Dilution Egg Count Equivalents for our }and-categories are very similar and essentially belong to group II above; the equivalents of 2+and 3+are close together and of group III; again 4+and 5+have similar Dilution Equivalents and both fall in group IV. To be sure, a certain number of our cases, averaged into the higher gplus hcategories, had egg counts in excess of 10,000 (category V) per gram of feces. These severe infections probably comprised less than one percent of the 3055 people examined. An additional 10% probably had a low-grade hookworm disease, while the remainder were subclinical. From these figures it is apparent that hookworm is a public health matter of some concern in Yamanashi Prefecture. SUMMARY 1. An epidemiologic survey of intestinal parasites was made in the population centers of Kissawa, Kofu City, Otsuka, Hikawa, Sancho and Futakawa in the Kofu valley area of Yamanashi Prefecture.

8 120HUNTER et al 2. A total of 99.5% of the 3055 people who were examined harbored intestinal parasites; 99.4% were infected with helminths and 53.9% with protozoa. The incidence of the individual parasites is summarized in Table Whipworm was encountered more frequently than ascaris, 91.6 and 88.8% respectively. 4. On the basis of incidence data there did not appear to be any correlation between the occurrence of hookworm and the various agricultural pursuits, such as the raising of rice, mulberries or grapes. 5. Schistosoma japonicum was found in about 65% of the individuals examined in two population centers, in about 30% of two others, and less than 5% in the remaining two. By multiple examinations an incidence of over 90% was shown to occur for children villages other than those included in the survey years of age in several 6. Endamoeba histolytica was present in 10.3% of those examined, with a peak of 15.8% in one rural village. The lowest incidence occurred in two communities on the valley floor, while the highest occurred in hillside villages. 7. Helminth infections appeared to be of moderate intensity, but a large majority of the people harbored 3 to 5 different species. Probably 10% had severe ascaris, and 1% severe hookworm disease. REFERENCES (1) Hunter, G.W.III, Hodges, E.P., Jahnes, W.G., Diamond, L.S. and Ingalls, J.W.Jr.: Studies on schistosomiasis. II. Summary of further studies on methods of recovering eggs of S. japonicum from stools. Bull. U.S. Army Med. Dept. 8: (2) Ritchie, L.S.: An ether sedimentation technique for routine stool examinations. Bull. U.S. Army Med. Dept. 8: (3) Tigertt, W.,D., Hunter, G.W.III and Ritchie, L.S. MS: Parasitological studies in the Far East. I. Methods and review of Japanese literature. (4) Wright, W.H., McMullen, D.B., Bennett, H.J., Bauman, P.M. and Ingalls, J.W. Jr.: The epidemiology of schistosomiasis japonica in the Philippine Islands and Japan. III. Survey of endemic areas of schistosomiasis japonica in Japan. Am. J. Hyg. 27: (5) Hunter, G.W.III, Ritchie, L.S., Kaufman, E.H., Pan, C., Szewczak, J.T., Yokogawa, M. and Ishii, N.: Parasitological studies in the Far East. IV. An epidemiologic survey in. Yamanashi Prefecture, Honshu, Japan. J. Parasit. 34 (Suppl.):35 (Abstract.)

9 PARASITOLOCICAL STUDIES IV121 (6) Hunter, G.W.III, Ritchit, L.S., Nagano, K. and Ishii, N.: Parasitological studies in the Far Fast. II. A preliminary report of an epidemiologic survey in Fukui Prefecture, Honshu, Japan. Jap. Med. Jour. 3. 6, (7) Ritchie, L.S., Hunter, G.W.III, Pan, C., Szewczak, J.T. and Ishii, N. MS.: Parasitological studies in the Far East. III. A preliminary report of an epidemiologic survey in Aomori Prefecture, Honshu, Japan. Jap. Med. Jour.3., 6., (8) Cort, W.W., Grant, J.P., Shoal, N.R. and Tseng, H.W.: Researches on hookworms in China. IX. Rice cultivation and hookworm infestation. Am. J. Hyg., Mono. Series No. 7: (9) Chang, K. and Tong, W.K.: Hookworm disease in Szechwan Province, West China. V. Surveys of hookworm infections in a rice district and among a group of vegetable gardeners. Am. J. Hyg., Mono. Series No. 19: (10) Cort, W.W., Grant, J.P., Stall, N.PI., Tseng, H.W.: Researches on hookworm in China. VIII. An epidemiological study of hookworm disease in the mulberry district of the Yarngtze Delta. Am. J. Hyg., Mono. Series No. 7: (11) Chang, K., Tong, W.K., Ch'in, H.T. and Li, C.H.: Hookworm disease in Szechwan Province., West China. II. Mulberry cultivation and hookworm infection. Am,. J. Hyg., Mono. Series No. 19: (12) Tang, C.C.: Sweet potato cultivation and hookworm disease in Fukien, South China. A.m. J Hyg., 50(2): (13) Chang, K.: Hookworm disease in Szechwan Province, West China. VII. The transmission of hookworm disease in Szechwan. Am. J. Hyg., Mono. Series No. 19: (14) Cort, W.W., Stoll, N.R., Grant, J.I.: Researches on hookworm in China. I. Problems and methods of attack. Am. J. Hyg., Mono Series No. 7:

10 122 HUNTER et al TABLE 1 INCIDENCE OF INTESTINAL PARASITES

11 IN YAMANASHI PREFECTURE PARASITOLOGICAL STUDIES IV 123

12 124 HUNTER et al Table 2 PARASITE DENSITY INDEXES FOR HELMINTHS IN ASSOCIATION WITH INCIDENCE \BY COMMUNITY * Parasite Density Index.