Japan. J. Med. Sci. Biol., 18, 1-17, 1965 TECHNIQUES APPLIED IN JAPAN FOR THE CONTROL OF ASCARIS AND HOOKWORM INFECTIONS •\A REVIEW•\ YOSHITAKA KOMIYA AND AKIO KOBAYASHI Department of Parasitology, National Institute of Health, Tokyo , Japan (Received : February 10th 1965) The quickest way to control and eradicate parasites is to break up their life cycle at its weakest point. In the cases of soil-borne parasites, techniques applied in the break- up of their life cycle include (1) repeated mass treatment of the infected population to eliminate the worms they harbor, (2) handling and treatment of night-soil to render eggs and larvae non-viable, and (3) procedure for the removal or inactivation of eggs on food . Among these, in Japan, the periodic mass treatments are recognized as the •gmain main pillar•h on which prevention of Ascaris and hookworm infections rests. The following is a brief summary of techniques developed and applied in Japan . MASS TREATMENT a) General considerations In a community, especially in a rural one, mass treatment is used for the purpose of rapidly reducing the total number of egg-producing worms and consequently of minimizing the chance of reinfection. After one mass treatment, the extent of reinfection diminishes and if a second mass treatment is performed prior to the time when the number of people positive for eggs reaches the initial pre-treatment level , the total worm burden, as well as the number of people infected, will decrease gradually. Repeated mass treatment in non-rural communities will also reduce the worm burden , provided that measures are effectively taken to avoid reinfection. b) Measurement of worm burden In order to assess the effect of mass treatment it is necessary to measure the total worm burden in a given community, before and after the treatment . This can be done by egg-counting technique but because of its complexity it is difficult to use it as a routine method in large-scale surveys. Its weakness lies in the fact that eggs cannot be recovered in cases of very light hookworm infection since the sample in which eggs are counted •\ usually 10 mg of stool •\ is too small for this. In Japan, the technique used for routine stool examinations is the direct smear for Ascaris eggs, and floatation in a saturated salt solution for hookworm eggs . Worm burdens are recorded as follows : + when egg number under the cover glass (18 •~ 18 mm) is less than 9, ++ when it amounts to 10-99 , and +++ when it is more than 100. The number of people positive for eggs, in relation to the total number of people examined, can be used for indicating roughly the average individual worm burden . 小 宮 義 孝 ・小 林 昭 夫(国 立 予 防 衛 生 研 究 所 寄 生 虫部) 1 2 KOMIYA et KOBAYASHI Vol. 18 Autopsies have shown that the average number of Ascaris per positive case was 5.1 when the incidence of infection was 40 %, whereas the majority (about 70 %) of the infected harbored only one worm when the incidence was 10 % or less (Komiya et al., 1963 a). As a result of mass treatment, decline in individual worm burden appears to occur more rapidly than the decline in over-all incidence. A field experiment on hookworm (Komiya et al., 1953) revealed that incidence fell from about 67 % to 13.5 % over a period of three years, whilst the average worm number decreased from the initial 32 to about 1 per positive case. c) Frequency of mass treatment and season in which it should be carried out When incidence is high it is well known that mass treatment for Ascaris infection given once or twice a year is insufficient to reduce the incidence because of the rapidity of reinfection. If the initial incidence is not too high, say 60-70 % or less, biannual treatments appear to be effective. With the assistance of the Gunma Educational Committee, the authors carried out biannual mass treatments for Ascaris infection among children and pupils in fifty schools. Prior to the initial performance of mass treatment 73 % of the children were positive. After one year this incidence was reduced by half (Fig. 1) and continued to be reduced in the same proportion the following years (Gunma Educational Committee, 1954). Table 1 shows the results of repeated mass treatments twice yearly given to children in 32 schools in Shinjuku Ward in Tokyo. Here the initial incidence (11.6 %) decreased to 2.2 % within five years. The effect of repeated mass treatments in controlling hookworm infection is considered to be about the same as that for Ascaris. Ascaris control is even more effective when mass treatment is crried out after the Fig. 1. Decrease in the incidence of Ascaris infection as a result of biannual mass treatments. Table 1. Decrease in the incidence of Ascaris infection as a result of biannual mass treatments 1965 CONTROL OF ASCARIS AND HOOKWORM INFECTIONS 3 infection has reached its peak, i. e. in May and October in Japan, when raw vegetables are mostly to be seen in the markets (Fig. 2) (Kobayashi , 1954; Yajima, 1955). In hookworm infection such treatment should be carried out in winter , owing to the low resistance of eggs and larvae to low temperatures (Fig. 3) (Kobayashi et al., 1959). Table 2 shows the results of experimental mass treatments performed in winter over a period of three years (Komiya et al., 1953). Here the initial worm burden (32.1 per the infected) decreased to about 1/30 (1.1 per infected) after two years. d) Performance of mass treatment In order to carry out mass treatment effectively the following is recommended. 1) Stool examinations : The performance of stool examinations of all people in a Fig. 2. Seasonal variation of Ascaris infection Fig. 3. The resistance of hookworm eggs to low temperatures Kobayashi et al., 1959) Table 2. Number of worms expelled after mass treatments (Komiya et al., 1953) 4 KOMIYA et KOBAYASHI Vol. 18 community prior to mass treatment is bound to be difficult, but it is essential that at least 80 % of the population is examined previously for eggs. To achieve this, health education is an absolute necessity. Simple posters, pamphlets and pictures should be utilized. Small groups should be invited to view slides and movies. 2) Technique for the recovery of eggs from stools : For evaluation purposes, stool examinations should be made before and after mass treatment, using a standardized technique. As mentioned above the two techniques which are recommended in Japan are : the direct smear with a 18 •~ 18 mm cover glass for Ascaris eggs (provided that the same specimen is examined three times) and floatation in a saturated salt solution for hook- worm eggs. The direct smear is sufficient for the recovery of fertilized Ascaris eggs even in mild infection cases. But when incidence is reduced the number of people discharging only unfertilized eggs was found to increase gradually. For instance, when the former become as low as 5 % or less, the latter accounts for 80 % or more of all the positives (Komiya et al., 1963 a). In such a case those discharging only unfertilized eggs are considered as harboring only one female, and the EPG of such a female is considered to be much lower than the EPG of a female producing fertilized eggs (Komiya et al., 1963 a). It seems that the •gthick thick smear technique with cellophane paper cover•h (Kato and Miura, 1954) enables the recovery of more unfertilized eggs. This technique has been officially recommended by the Parasite Control Association of Japan for use in a nation- wide survey of Ascaris and hookworm infections. 3) Selection of anthelmintics : For mass treatment to be successful an anthelmintic should be selected in advance which must be very effective with few side-effects, inex- pensive and easily tolerated. With the above in mind the Ministry of Health and Welfare of Japan (1961) recommended the following anthelmintics for use in mass treatments of ascariasis and ancylostom iasis. For ascariasis : 1. Santonin 2. A combination of santonin and kainic acid 3. Piperazine preparation 4. A combination of santonin with oil of chenopodium For ancylostomiasis : 1. Tetrachlorethylene 2. 1-bromo-2-naphthol 3. 4-iodothymol 4. Bephenium hydroxynaphthoate Among these santonin with kainic acid and 1-bromo-2-naphthol are particularly recommended for Ascaria and hookworm infections, respectively. Both anthelmintics have been developed in Japan and proved to be highly effective with few side-effects. It is possible that these drugs may not yet be widely used outside the country. Brief inf ormations may therefore be necessary under the separate chapter as to their an thel- mintic activities and toxicities. In some communities, it will be necessary to determine the predominant hookworm species involved prior to drug administration so that a better compound is given. For such a purpose, the cultivation technique using a filter paper (Harada and Mori, 1951) may be conveniently adopted. 1965 CONTROL OF ASCARIS AND HOOKWORM INFECTIONS 5 4) Assessment of mass treatment : In order to assess the results obtained after treatment it is necessary to perform stool examinations. Morishita working on Ascaris (1953) and Komiya et al. (1954 a) on hookworm have shown that Ascaris is completely expelled within 14 days and hookworms within 4 days. As a safety measure another week should be added to the expulsion period and stool examination should be performed 3-4 weeks after treatment for Ascaris, 2-3 weeks for hookworms, or if convenient 3-4 weeks in both cases. The anthelmintic action of a given drug against Ascaris or hookworm infection may possibly be evaluated according to one of the following criteria: (1) the rate of ex- pulsion of the worms, (2) the egg-reduction rate, and (3) the egg-negative rate.