STUDY OF INTESTINAL PARASITES. 81 



In some of the studies the number of persons infected with intestinal 

 worms alone is not stated as indicated in the table. It is probable that 

 the findings at San Antonio and Maluno do not differ essentially from 

 those in other parts of Luzon, excepting Tiiguegarao, where approxi- 

 mately 10 per cent less of the population were infected than elsewhere. 



It is noteworthy that the number of infections with intestinal worms 

 per 100 persons examined was decidedly lower in the Cagayan Valley than 

 in other parts of the island ; this probably is due to the relatively low per- 

 centages of whipworm infections encountered in that locality. 



The striking features of the findings at San Antonio and Maluno are 

 the high percentage of persons infected with the hookworm and the low 

 percentage with the whipworm (Trichuris). 'Eissler and Gomez found 

 45.38 per cent of the 802 individuals and 60.58 per cent of the adult males 

 examined at Santa Isabel (which is also a tobacco hacienda) infected 

 with the hookworm whereas 54.37 per cent of the 4,278 persons and 74.89 

 per cent of the adult males composing the present series harbored the 

 parasite. That is, 8.99 per cent more of the general population and 14.31 

 per cent more of the adult male population was infected with the hook- 

 worm than heretofore reported for any section of the Philippine Islands. 

 Garrison's series of 4,106 cases examined at Bilibid prison and which 

 gave 52.00 per cent of hookworm infection, was composed almost entire- 

 ly of adult males. 



In my opinion, three factors are acting to produce a high percentage of 

 hookworm infection at the haciendas, namely, the nature of the soil, the 

 tobacco plants, and the occupation of the people. The soil is composed of 

 clay with which sand is generously admixed, the tobacco plants furnish 

 shade-conditions which are favorable for the propagation of the hook- 

 worm, and the cultivation of the tobacco keeps the people in the field daily 

 during the greater part of the year. The belief that the infections are 

 obtained in the fields is supported by the facts that the hookworm percent- 

 age increases rapidly when the age is reached at which work in the fields 

 is begun,* that males, who are in the fields more than females, give a 

 higher percentage of infection than the females, and that a greater 

 percentage of persons are infected in the lowlands than in the uplands. 



The findings in regard to the whipworm were quite as unexpected as 

 those for the hookworm. Prior to the work in the Cagayan Valley, 

 statistical studies had shown Trichuris to be very common in the Phil- 

 ippine Islands, Garrison and Llamas finding as high as 87.60 per 

 cent of 385 women and children of Manila infected with it. Bissler and 

 Gomez found 25.90 per cent of the persons examined at Tuguegarao 

 and 6.23 per cent of those examined at Santa Isabel to be infected with 

 the same parasite. (See Table III.) At Maluno only 4.75 per cent 



* That is, about 7 years. 

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