21,6 Mendoza-Guazon: Schistosomiasis in the Philippines 563 
specificity in the choice of an intermediary host and adaptability 
to a new host. This fact is true of S. hematobium, for the 
development of cercarize in both Bullinus contortus and B. 
dybowski has been reported by Leiper(19) in Egypt, and in 
Physopsis africana by Cawson(3) in South Africa. 
If the intermediary host does exist here, it can find in this 
country all the conditions favorable for its endemicity and 
spread; namely, warm climate, continuous rain, evergreen 
vegetation (which supplies abundant food for the snails), un- 
sanitary methods for the disposal of human waste, the habit 
of our laborers compelled by necessity to wade the rice fields 
of going barefooted and, above all, the habit of eating partially 
cooked snails, which in some places are used as food, especially in 
time of famine. 
Even if the intermediary host is not found in these Islands, 
the immigration of people who eat this snail and the possible 
entrance of infected individuals are a possible source of in- 
fection. Cort(8) found that this snail can resist drying during 
the shipping time from Japan to California, due to its ability 
to close the opening of its shell with its operculum, and that 
this resistance is limited to three months. Although he found 
that the cercaria within the snail is affected by desiccation 
and that the infected snails die more quickly than the un- 
infected, the distance from Japan to the Philippine Islands is 
so short that desiccation cannot be relied on to kill the snails 
when imported into our country. 
AGE, SEX, AND OCCUPATIONAL INCIDENCE 
Table 2 shows clearly that the infection is acquired at ages 
when the male has to work outdoors for his living. 
TABLE 2.—Age, sex, and occupational incidence in schistosomiasis. 
Age in years. 
Author, Sex. | Occupation. 
15-20 | 20-80 | 30-40 | 40+ 
Woolley... --4- nn nd ono = nono s ene e] stains == |-4------|-------: 2 M Prisoner. 
Phalen and Nichols... ------------------|-------- LESS ase ger M Soldier. 
Pe Geto oi cn ee ah ee ie n= ~~ p ey Apeee eta pers ne at M Laborer. 
This report .n0ci ciate y- -cns -neeyeaseree 3 Btge ey 2 M Prisoner 
and labor- 
ers. 
The number of cases reported, the lowered resistance of the 
infected individuals, and the danger to the community must 
189549-——4 
