DIAGNOSIS OF DISEASES CAUSED BY PAEASITIC WORMS 39 



with Schistosoma haematobium and Paragonimus westermanii 

 the eggs escape with the urine and sputum respectively, so 

 diagnosis of these forms must be made by microscopical 

 examination of these media. In the Filaridae, the larvae 

 are carried from one host to another by the mosquito and 

 diagnosis is made as in malaria by the examination of blood 

 smears. In the majority of these diseases however, the eggs 

 or larvae of the worms escape with the feces and an accurate 

 diagnosis can be made by microscopical examination of the 

 stools. 



In diagnosis by fecal examination the technique used is 

 of very great importance. The number of worms present 

 varies greatly in the different cases and even with the best 

 possible technique it is probable that not all cases will be 

 detected. Since in the lighter infestations there are usually 

 no symptoms present such individuals are usually classed 

 as "carriers." Since with almost all the parasitic worms 

 of man an injurious effect is produced in light infestations 

 as well as heavy, although there may be no noticeable 

 symptoms, and since every "carrier" is a potential spreader 

 of the disease it would seem that the greatest possible 

 accuracy in diagnosis is desirable. There are however other 

 factors to be considered. Greater accuracy usually means 

 fewer examinations. When as in hookworm campaigns 

 the examinations to be made are many and the workers 

 few, a compromise must be made between thoroughness and 

 speed. Under hospital conditions where there are only a 

 comparatively few examinations to be made it would seem 

 to be advisable to use the slower but more critical methods. 

 In field campaigns or surveys, however, where thousands of 

 examinations must be made, often by microscopists who 

 have no special scientific training, and under conditions 

 where it is difficult to obtain or use complicated apparatus, 

 simple, more rapid methods of examination would certainly 



