ANIMAL PARASITES 153 



this country, where but httle pork is eaten raw. Infec- 

 tion is usually due to eating raw (merely smoked) ham. 



Hookworm. — A disease common in Porto Rico and in 

 the Southern States is due to infection with hookworm. 

 This parasite appears to live only in man, and infection 

 usually takes place through the sldn, especially in those 

 walking, barefooted. The first symptoms are those due 

 to the penetration of the skin by the young w^orm, and 

 constitute what is known as "ground itch." Subse- 

 quently the parasites enter the intestines and give rise 

 to ver}^ characteristic symptoms, chief among which are 

 anemia and laziness. The worm is sometimes spoken 

 of as the ''lazy worm." 



Filaria. — The disease known as "filariasis" and ''ele- 

 phantiasis" is due to infection with a tiny worm which 

 invades the blood and lymph passages. This infection is 

 transmitted by a species of mosquito. 



So far as the nurse is concerned, the description of the 

 mode of infection, as just presented, should suffice to 

 indicate the mode of prevention. 



Pediculosis. — Infestation with lice, called pediculosis or 

 lousiness, is important because lice are known to spread 

 disease (typhus fever, trench fever, and probably other 

 infections). The body louse is said to have about 5000 

 offspring in the course of two months. The eggs, called 

 "nits," are slightly elongated, and fastened to the hair of 

 the host or clothing. They hatch out in three or four days 

 and are sexually mature in about eighteen days. Lice 

 are parasitic, blood-sucking insects, and three species are 

 known to infest man. (For methods of combating lousi- 

 ness see under "Disinfestation," page 1G9.; 



