CHAPTER IX 



THE DETERMINATION OF HELMINTH 

 INFECTIONS THROUGH FECAL EXAMINATIONS 



TECHNICAL SUGGESTIONS 



As an introduction to the methods of determination of parasites 

 in the living host, this practicum is confined to the microscopic 

 examination of fecal samples for helminth infections. Most of the eggs 

 to be considered have already been seen in the course of the practi- 

 cums, but it is essential that the student learn to identify them and 

 to distinguish them from the miscellaneous debris of fecal samples. 



If time and the size of the class permit, the entire preparation and 

 examination should be carried out by each student. For this purpose 

 fresh feces of cats and dogs, preferably of young animals, may be used. 



Ordinarily it is necessary to rely on formalin-preserved material, 

 arid such may often be from human sources. Samples from infected 

 patients can be secured through the aid of physicians and hospital 

 technicians, sedimented, and preserved in a liberal quantity of 10 

 per cent formalin. If there is considerable coarse debris, the sample 

 should be passed through a fine-meshed sieve. (The tea-strainers 

 available at the five-and-ten-cent stores make a convenient tool for 

 this purpose.) After each using they should be flamed or thoroughly 

 washed to avoid contamination of subsequent samples. 



Eggs of a number of species of helminths affecting man, or of very 

 closely related species, may be obtained from the parasites of various 

 animals and should be stored in formalin as individual samples. In 

 order to obtain quantities of eggs for class work the samples may be 

 increased by adding the teased uteri of mature specimens. Unknowns 

 may be prepared by combining several species after the study of the 

 separate samples. 



As illustrations of useful forms from animals may be cited the 

 ascaris of the pig, ascarids, hookworms, and trichurids of cats and 

 dogs; Taenia and Dipylidium eggs from cats and dogs; Hymenolepis 

 eggs from rats and mice, or, for more general study, from chickens. 

 The sheep liver fluke affords a typical fluke egg, but even the ever 

 available frog flukes may be used. The oocysts of rabbit coccidia 

 should be studied as illustrations of forms that may be confused with 

 helminth eggs. 



One or more of the important schistosomes of man should be 

 available. Formalin-preserved material or prepared slides of eggs of 

 these are obtainable from dealers. 



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