Cnapter 11 



PARASITES 



By Walter E. Heston, National Cancer Institute.* 



Introduction, 349. Protozoa, 350. Amoebae, 350. Flagellates, 351. Haemo 

 llagellates, 353. Coccidia, 354. Sarcosporidia, 357. Prevention and control of 

 protozoan infections, 358. Helminths, 359. Trematoda, 359. Cestoda, 359. 

 Nematodes, 364. Arthropods, 370. Lice, 370. Fleas, 371. Bedbugs, 372. Mites, 

 374. Control measures for other insect pests of the laboratory, 376. BibUography, 

 377- 



Introduction 



The house mouse has not been shghted by the evolutionary processes 

 developing parasitic forms. Over a dozen protozoa have been described as 

 parasites or commensals living in its blood stream, digestive tract, and 

 various other internal organs. Of the nematodes, Hall (17) lists twelve 

 species for which the mouse may act as host, and describes from the rat a. 

 thirteenth which other workers have found in the mouse. A number of 

 species of tapeworm infest it, the adult forms of some living in its digestive 

 tract and the larvae of others in its tissues. Also, to this group of internal 

 forms might be added the mites, lice, bedbugs, and fleas which may occur 

 as external parasites. 



Many of these parasites are of utmost importance to the research worker 

 who is employing mice in his experiments. Although probably compara- 

 tively few of the forms have much influence on the well-being of the mouse 

 in the natural state, under laboratory conditions and especially under 

 experimental conditions they may develop into serious factors not only 

 because of their deleterious effects upon the mouse, but also because they 

 may act as influencing factors introduced into the experiments. Animals 

 used in testing deficient diets may have their resistance so lowered that 

 external or even internal parasites may get out of control. The death of a 

 mouse bearing a large tumor may be affected not merely because of the large 



* Formerly National Cancer Institute Research Fellow at the Roscoe B. Jackson 

 Memorial Laboratory. 



349 



