PHYLA NEMATHELMINTHES, NEMATOMORPHA, AND ACANTHOCEPHALA 



155 



Giant kidney worm, 

 Dioctophyma renale, 

 from fish-eating 

 mammals 



Free-living horsehair worm, 

 Paragordius varius 



Figure 81. Roundworms, parasitic and free-living. 



into the lumen, attach themselves to the 

 mucosa, and develop into adults. 



PARASTIC ROUNDWORMS 



OF MAN 



Ascaris lumbricoides 



Human beings are parasitized by at least 

 45 species of roundworms, some of which 

 are widespread and cause great suffering and 

 thousands of deaths annually. Ascaris lum- 

 bricoides is an important human parasite. 

 One survey in the tropics showed that in 

 over 200 natives studied, only one did not 

 suffer from ascariasis. \Vhen large numbers 

 of the ascaris larvae pass through the lungs, 

 inflammation is set up and generalized pneu- 

 monia may result. The adults may be pres- 

 ent in the intestine in such large numbers 

 as to produce fatal intestinal obstruction. 

 One thousand to five thousand worms have 

 been recorded in a patient, but even a hun- 



dred worms can cause a blockage that is 

 fatal. One of the most frequent complaints 

 of a patient suffering from ascariasis is 

 abdominal pain or discomfort. Nervous 

 svmptoms such as headache or convulsions 

 may appear as a result of the secretion of 

 toxic substances by the worms. Fortunately, 

 several drugs are available which remove 

 the worms. The amount of infection with 

 ascarids is a measure of the sanitation pres- 

 ent in the region. In some areas and eco- 

 nomic strata in the United States there is 

 still considerable worm infection. Ascariasis 

 occurs more frequently in children than in 

 adults because of the carelessness of chil- 

 dren with regard to sanitary matters. Infec- 

 tion can be prevented by enforcing sanitary 

 practices. 



Hookworms 



The hookworms, Ancylostoma duodenale, 

 and Necator americanus (Fig. 82) are also 

 widespread and injurious; about 95 per cent 



