Xii. an Epidemiologic Survey in Shizuoka Prefecture, Honshu, Japan
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Jap. J. M. Sc.& Biol., 9, 165-177, 1956 PARASITOLOGICAL STUDIES IN THE FAR EAST XII. AN EPIDEMIOLOGIC SURVEY IN SHIZUOKA PREFECTURE, HONSHU, JAPAN LAWRENCE S. RITCHIE, GEORGE W. HUNTER III1), ROBERT E. FREYTAG, CHIATUNG PAN, MUNEO YOKOGAWA2) AND SUNG SHENG LIN With the Technical Assistance of MITSUAKI SHIMIZU, YOSHIMASA HISHINUMA, SOICHI ASAKURA AND CARROL B. KNOX Department of Medical Zoology, 406th Medical General Laboratory APO 343, San Francisco, California and The National Institute of Health, Tokyo, Japan (Received: July 16th, 1956) A parasitologic survey of human parasitic infections was made in Shizuoka Prefecture, Japan, during August and September, 1950 (Ritchie et al., 1951a). The objectives included a determination of (i) the incidence of infections, (ii) helminth densities,(iii) factors predisposing infections,(iv) the status of schistosomiasis,(v) status of paragonimiasis and filariasis, and (vi) the efficiency of the intradermal test for the diagnosis of paragonimiasis. METHODS Single-stool examinations were made on 2278 persons in 22 communities of Shizu- oka Prefecture. Survey centers were selected independently of knowledge regarding the status of parasitic infections, with the exception of schistosomiasis, paragonimiasis and filariasis. For these three, localized occurrence necessitated making selections on the basis of a priori knowledge of distribution. All specimens were examined by means of both the 406th MGL (formalin-ether) and the AMS III concentration technics, the latter being especially effective for eggs of Schistosoma japonicum and Paragonimus westermani. Further information on occurrence of schistosomiasis was obtained by intradermal tests on 470 additional persons. Sputum concentrates were examined for a group with a history of para- gonimiasis. Scotch tape swabs were taken on 427 children included in the survey to detect pinworm infections. Blood specimens from 350 persons in a suspected filaria- 1) Col., USA (Ret .). Present address: 109 Bryker Drive, San Antonio, Texas 2) Present address: Institute of Para ,sitology, Chiba University, Chiba, Japan 165 166 RITCHIE et at Vol. 9 1956 PARASITOLOGICAL STUDIES, XII 167 sis area were examined by the Knott concentration method for microfilariae. Details of these technics and procedures have been reported previously (Tigertt et al., 1952). PHYSICAL AND BIOLOGIC CONDITIONS Description of localities surveyed: Shizuoka Prefecture is located on the Pacific Coast of Central Honshu, about 100 miles southwest of Tokyo. It is bounded on the north by Yamanashi Prefecture, where one of our surveys was made, and on the south by Suruga Bay. Sparcely populated mountainous areas (including part of Mt. Fuji) predominate, but coastal areas and several broad inland valleys support dense populations. One of the major paragonimiasis centers of Japan is located to the east of Numazu along the Kano River. The principal schistosomiasis center is a mile-wide rectangular area extending west- ward from Numazu for a distance of about 10 miles. It is bounded on the south by the shoreline Tokaido highway and railroad, and to the north by a parallel country road. A suspected filariasis center is located in a valley extending inland from Yoshiwara at the western end of the schistosomiasis area (See Fig. 1). Most of the population centers selected were rural, but some were at the perimeter of urban centers and consequently included other than farmers; one was a fishing center (Ganyudo) and another a business section of Numazu (Ote Machi). Conditions of living : Though typical of Japan, living conditions reflected an above-average economic status. This was linked with industrial pursuits, and the fruit and tea crops for which Shizuoka is noted. Rural dwellings, which were concentrated in villages, included the thatch- or tile-roofed house, stable, compost shed and storage structures, all arranged around a central dooryard. Houses were commonly neat and clean, although some were untidy and had a sour smell with uneaten food and dirty dishes in evidence. Kitchens usually had a dirt floor while the rest of the house had typical straw mats placed over wooden floors. Pumps were in general use, being associated about equally with driven and dug wells ; the latter were commonly sealed. Springs supplied household re- servoirs at Hita and Kanaoka, and tap water was in common usage in Izumi, Harada and Numazu. Where accessible, flowing streams were used for washing clothes, vegetables and sometimes dishes. Crops and livestock : Extent of rice culture varied from 30 to 90% in different areas. Tea and vegetables predominated in the foot hills. Except in strictly urban sections, most homes had dooryard gardens fertilized by night soil. There was an average of one cow or horse per dwelling, actual numbers varying according to available grass on untilled foothills or river levees. Two villages reported a considerable number of pigs, which were penned, and most families kept a few chickens. Fertilizers : Livestock was sufficient to furnish considerable manure, which 168 RITCHIE et at Vol. 9 with refuse and straw was composted. Commonly, a portion of available night soil was added to the compost piles. Chemical fertilizers were used in varying amounts in different villages. About 60 families were interrogated regarding the processing and use of night soil. The amount processed by composting varied from 0 to 80% by family and the extent of this practice varied consider- ably in different communities. Otherwise the liquid night soil was stored for a varying time, rarely exceeding one month, in open cement tanks constructed in the ground. Composted materials were applied on dry fields, paddy fields, and gardens. Liquid night soil was limited to dry fields and gardens, being used only occasionally for wet rice culture. Night soil was not utilized in any form for cultivation of tea or sweet potatoes, thus excluding two likely avenues of hookworm transmission. Whereas farmers were said to apply some chemical fertilizer on vegetables, dooryard gardens of non-farming families were usually fertilized directly from household toilets. Only about one-third of the , farm families interrogated reported direct applications of toilet receptacle contents to gardens. There was no consistent design in the processing and use of night soil that suggested a deliberate plan to suppress transmission of helminths; rather, the practices appeared to be agricultural expediencies. RESULTS AND DISCUSSION Occurrence of intestinal parasites for the entire survey (Table 1): One or more parasites were diagnosed for 93.6% of all persons examined; 91.8% har- bored helminths and 33.5% were found to be infected with one or more intestinal protozoa. Total numbers of helminth and protozoan infections identified consti- tuted an average of 1.9 and 0.45 infections, respectively, for each person examined. This is quite in contrast to adjoining Yamanashi Prefecture where corresponding averages were 3.4 and 0.85 (Hunter et al., 1951a). There were four examinees who harbored seven different parasites ; 31 had six species, 93 had five and 274 had four. Ascaris lumbricoides was the most common parasite, for which the overall prevalent rate was 79.9 %. The prevalent rate of other common helminths was Trichuris trichiura 58.3%, hookworm 27.4%, Trichostrongylus sp. 8.7% and . Enterobius vermicularis 56.4% (by Scotch tape swabs on children). No in- fections of Strong yloides stercoralis were encountered; this parasite is encoun- tered only infrequently in Japan. For the entire survey the prevalent rate of S. japonicum and P. westermani was 1.8 and 1.9 % respectively, and Clonorchis sinensis and Metagonimus yokogawai each occurred to the extent of about 1 %. Only four tapeworm infections were found, two each of Hymenolepis nana and H. diminuta. Echinostome eggs were recovered from two persons and Fasciola hepatica from one. Heterophyid-like eggs were noted in 36 persons (1.6%). In general the helminthic infections were lower than for the Kof u Valley in. 1956 PARASITOLOGICAL STUDIES, XII 169 adjacent Yamanashi Prefecture (Hunter et al., 1951a). Endamoeba histolytica was found in only 4.4% of the persons examined. For the other protozoa the figures were E. coli 22.6%, Endolimax nana 13.6%, Iodamoeba butschlii 0.6%, Giardia lamblia 4.1% and Chilomastix mesnili 0.2%. Table 1. Summary of intestinal parasites in Shizuoka Prefecture * No. positive/No. examined by scotch tape swab Frequency of the intestinal protozoa was only about one-half that for Yamanashi Prefecture. Comparison of parasitism in the various communities surveyed (Table 2): Parasitosis by community ranged from 87 to 99%. Considering only the helminths, the corresponding figures were 83 and 99 %. The occurrence of one or more protozoa ranged from 20 to 48%. The ascaris infection rate varied from 61 to 93%; whipworm from 34 to 85% and hookworm from 4 to 55%. In one community no infections of Trichostrongylus infections were found, in contrast to 26% which occurred in the largest urban center (Numazu). On the basis of small numbers of cases, the infection rate of pinworm was as high 170 RITCHIE et al Vol. 9 Table 2. Prevalent rate of intestinal parasites by community * No . positive/No. examined by scotch tape swab Table 2 (Continued). * No . positive/No. examined by scotch tape swab 1956 PARASITOLOGICAL STUDIES, XII 171 Table 2 (Continued). * No . positive/No. examined by scotch tape swab Table 2 (Continued). * No. positive/No. examined by scotch tape swab 172 RITCHIE et al Vol. 9 as 89 %. Maximum rates of M. yokogawai and C. sinensis were 8 and 5% respectively. E. histolytica was limited to 1 % in three communities and 5 % or less in 14 of the 22 population centers surveyed. The highest prevalent rate encountered was 9%, which occurred in two villages. Endamoeba coli varied from 11 to 32%, E. nana from 3 to 30% and Giardia did not exceed 9%. Kitaema was the Table 3. Parasite density index (PDI) by community for ascaris, whipworm and hookworm * Parasite Density Index is based only on positive cases.•¬ High factor due to one of the four cases.