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Comparative Parasitology 68(2) 2001 - Peru State College

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264 COMPARATIVE PARASITOLOGY, <strong>68</strong>(2), JULY <strong>2001</strong><br />

was recovered from the rats collected in the<br />

paddy and hilly areas but not from those in the<br />

residential area.<br />

The differences in species composition and<br />

prevalence among the habitats could be explained<br />

by the biological characters of each<br />

helminth and by the environmental conditions.<br />

Because members of Notocotylus require a<br />

freshwater snail as the intermediate host (cf.<br />

Yamaguti, 1975), their presence in the paddy<br />

fields is reasonable. The hilly area surveyed in<br />

the present study contained many small ponds<br />

that might provide habitats for the snails. Also<br />

not unexpected is that G. neoplasticum and M.<br />

moniliformis were found only in the rats captured<br />

around the houses, because their intermediate<br />

hosts, usually cockroaches, are abundant<br />

in the residential areas. Nippostrongylus<br />

brasiliensis and Strongyloides spp. require<br />

moist soil for their embryonic and larval development<br />

and transmission. Their low prevalence<br />

or absence in the residential areas<br />

seems to be due to the dried soil around the<br />

houses in that season. Syphacia muris, the<br />

only helminth with relatively stable prevalence<br />

among the habitats, has a quite simple<br />

life cycle passed nearly entirely within the<br />

body of the host, and hence, its prevalence is<br />

less affected by the external environment.<br />

We are deeply indebted to Dr. G. G. Musser,<br />

American Museum of Natural History, for his<br />

kindness in identifying the rat species and to<br />

Dr. S. Kamegai, Meguro Parasitological Museum,<br />

for his kind consultation on Notocotylus<br />

sp.<br />

Literature Cited<br />

Durette-Desset, M. C. 1970. Caracteres primitifs de<br />

certains Nematodes Heligmosomes parasites de<br />

Murides et de Cricetides orientaux. Definition<br />

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