The parasitic soil nematodes, referred to near the 

 beginning of this chapter, spend the active part of 

 their lives in plant hosts, but many have inert cysts 

 that have been known to survive in soil for many 

 years, one as long as thirty-nine years. Attempts to 

 control their depredations range from crop rotation 

 to chemical fumigation, flooding of the soil, or en- 

 couraging the growth of fungi that trap nematodes. 

 None of these methods is completely successful. The 

 sugar beet eelworm, Heterodera schachtU, referred 

 to earlier as the first nematode known to infest crops, 

 is restricted to the roots of a few plant species. The 

 potato-root eelworm, Heterodera rostochiensis, also 

 attacks tomatoes, and it causes great losses from Ire- 

 land and Great Britain to Germany and most of west- 

 ern Europe except Norway. The root-knot nema- 

 todes, said to be a number of distinct species of the 

 genus Meloidogyne, infect nearly a thousand varie- 

 ties of plants, at least seventy-five of them garden 

 and field crops, fruit and shade trees. These are 

 mostly warm-climate nematodes, but under glass 

 they flourish anywhere. In England they do great 

 damage to tomatoes and cucumbers in commercial 

 greenhouses unless controlled by steam sterilization, 

 an effective method where the soil used is limited in 

 quantity. 



Man's struggle with parasitic roundworms was re- 

 corded about 1550 B.C. in the Ebers Papyrus, named 

 for the archaeologist who made the first translation. 

 Found in 1872 in a tomb in the Nile valley near 

 Thebes, the papyrus is a collection of remedies 

 against the various diseases that harassed the ancient 

 Egyptians. To "expel the roundworm in his belly," it 

 advises the physician to try thirty-two different reci- 

 pes, with ingredients ranging from pomegranate roots 

 and red ochre to turpentine and goose fat. Old Chi- 

 nese writings, one from 217 a.d., speak of "the long 

 worm," 5 to 6 inches or up to 1 foot in length. The 

 size and symptoms are those of Ascaris Iniuhricoides, 

 which may even reach 14 inches. It is thought that 

 man picked up this long-time companion when he 

 started to domesticate pigs, and in the process also 

 domesticated his own human strain of worms. The 

 ones that attack man and pig look identical, but they 

 do not readily exchange hosts. Nevertheless, both 

 pigs and dogs ingest the eggs of the human parasite 

 and help to spread them about to small children play- 

 ing outdoors. Prevention of infection with Ascaris 

 eggs must begin with sanitary disposal of human fe- 

 ces and with teaching young children to wash their 

 hands before eating. Even in parts of the world 

 where human feces are used as fertilizer to grow 

 leafy vegetables, the most important source of in- 

 fection is direct contamination through the hands. 

 Though a female Ascaris may lay 200,000 eggs daily, 

 many hazards beset the eggs: drying, too high or too 

 low temperatures, and the sanitary plumbing or 



sometimes cleanly habits of men. When the shelled 

 eggs do find their way back to the mouth, they al- 

 ready contain young larvae, and these hatch in the 

 intestine, burrow into blood vessels, and are carried 

 to liver, heart, and lungs. In the lungs they take hold, 

 make their way back to the trachea and throat, and 

 down to the intestine again, this time arriving with 

 size and health improved by travel. They bite the 

 intestinal wall, sucking in tissue juices, and also tak- 

 ing the digested food of the host. Most of the really 

 serious damage is done by the young worms as they 

 travel, but even the adult is a very unreliable para- 

 site. It may puncture the intestinal wall or wander 

 up the bile duct, with fatal results. 



The trichina worm, Trichinella spiralis, is much 

 less widespread in the world, and almost entirely ab- 

 sent from the tropical regions that have more than 

 their share of other parasitic worms. In arctic regions 

 it is common among Eskimos, and it does occur to 

 some extent in Mexico and temperate South Amer- 

 ica. But chiefly it is a parasite of Europe and the 

 United States, where it is encouraged in its efforts to 

 keep going by the habit of feeding garbage, which 

 usually contains pork scraps, to pigs. Wherever gar- 

 bage is fed to pigs as a method of disposal in larger 

 American cities, the incidence of trichinosis is high. 

 In the United States this applies chiefly to the North 

 Atlantic seaboard and to California. Many of the 

 most serious cases are concentrated among people 

 who enjoy various kinds of raw sausage and who 

 make it themselves from a single but highly infected 

 hog. Most infections are due to eating raw or under- 

 done pork, occasionally bear or walrus meat. In the 

 United States fewer than six hundred clinical cases a 

 year are clearly diagnosed, and of these less than 5 per 

 cent are fatal. But many serious infections are mis- 

 takenly said to be intestinal flu. food poisoning, or 

 typhoid fever. Since the estimated incidence in the 

 United States, as determined from examination of 

 the diaphragm at autopsy, ranges from 5 per cent in 

 New Orleans to more than 27 per cent of the people 

 in some northern and western cities, the vast major- 

 ity of cases must go undetected or end in medical 

 statistics as "psychosomatic" or other illness. Perhaps 

 the milder symptoms of trichina worm infection are 

 simply less severe than the weakness, diarrhea, ab- 

 dominal pains, nausea, fever, puffy eyes, and ex- 

 treme muscular pains that characterize fatal attacks. 

 The adult trichina worm is a tiny intestinal parasite, 

 but serious or fatal results are attributable to the 

 even smaller larval worms as they burrow through 

 the intestinal wall and enter lymph or blood ves- 

 sels, become distributed about the body, then bur- 

 row through every tissue or organ to settle down in 

 striated muscle tissue. There they grow to be ^ •_..-, of 

 an inch long, ten times their larval burrowing size. 

 They become sexually differentiated, roll into a spi- 



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