3 54 Constant 



the Panama canal was due as much to 

 our war against mosquitoes as to our 

 engineering skill. Draining of marshes, 

 screening of houses, and isolation of the 

 human carrier were measures that proved 

 successful; but they could be carried out 

 only in a relatively small area. There are 

 still great areas where mosquitoes are 

 plentiful and we are far from having 

 wiped out mosquito-borne diseases even 

 in our own country. 



The larger parasites. There are many 

 important diseases that have been barely 

 mentioned in the preceding pages. These 

 are the diseases caused by worms of vari- 

 ous sorts. These larger parasites damage 

 the body in quite a different way from 

 germs. We do not develop immunity to 

 such diseases. AH we can do is to attempt 

 to keep the parasites from entering the 

 body and to fight them with drugs. 



Hookworm disease. In many parts of 

 the world, where the climate is suitably 

 warm, large numbers of people have 

 hookworm disease. There are probably 

 as many as two million persons suffering 

 from hookworm in the United States. 

 The worms do not kill their host. They 

 cause anemia which makes the host feel 

 continually tired. Before measures were 

 taken to stop the spread of hookworm a 

 large proportion of the population of 

 certain states was infected with the 

 worm. 



The hookworm belongs to the group 

 of roundworms. It is like a tiny white 

 thread, scarcely visible to the naked eye 

 (1/25 of an inch in length). It spends 

 part of its life in the soil and enters its 

 host by boring through the skin of the 

 foot. Children are therefore most likely 

 to become infected because they often 



Care Is Needed for Health unit vi 



go barefoot. Once in the body, the 

 hookworm enters the veins, is swept to 

 the heart, and from there to the lungs. 

 Again it bores. And this time it enters 

 the air passages of the lung. In boring 

 from the veins into the lung it damages 

 lung tissue, thus making the host more 

 susceptible to tuberculosis. From the 

 windpipe it passes into the alimentary 

 canal where it spends the rest of its life 

 and where it does great harm. The worm 

 attaches itself to the wall of the intestine 

 and feeds upon the blood. It secretes a 

 substance which keeps blood from clot- 

 ting. In this way the worm has a steady 

 flow of food. Since the blood fails to 

 clot, the host is constantly losing blood 

 even when the worm is not feeding. It is 

 this loss of blood which causes anemia. 

 As the parasites develop they reproduce 

 in large numbers. The eggs pass out of 

 the intestines with the excretions and get 

 into the soil. Here each egg changes into 

 a larva which may find its way again into 

 another human host. 



Drugs have been discovered which 

 kill the hookworm in the host. Sanitary 

 precautions can be taken to keep the 

 larvae out of the soil. Also, shoes can be 

 provided for people who cannot afford 

 to buy them. Spreading education and 

 establishingr a higher standard of living 

 are the best ways of getting rid of the 

 hookworm. Try Exercise 9. 



Trichinosis. Trichinosis (trick-i-noh'- 

 sis) is a disease of men and pigs caused 

 by a relative of the hookworm. Men get 

 the disease by eating infected pork 

 which is raw or not thoroughly cooked. 

 Once the worms get into the intestines 

 of man they find favorable conditions 

 and develop rapidly. They reproduce, a 



