THE INTERNAL PARASITES OF RATS AND MICE IN THEIR 

 RELATION TO DISEASES OF MAN. 



By CH. WARDELL STILES, Chief, and CHARLES G. CRANE, B. S., Assistant, 

 J>ii ision of Zoology, Hygienic Laboratory, United States Public Health and Marine- 

 Hospital Service. 



SUMMARY. 



Rats and mice may harbor 11 species of internal parasites which come into consid- 

 eration as possible or established parasites of man. From this point of view, 7 

 of the parasites are of more academic interest than practical importance. The rat 

 may, however, be viewed as the practical, theoretical, and permanent reservoir for 

 one zooparasitic disease (trichinosis) of considerable importance, and of at least one, 

 perhaps two, other zooparasitic infections ("Lamblia duodenalis" and Hymenolepis 

 diminuta) of much less importance. Its possible future role in connection with sleep- 

 ing sickness should not be entirely ignored. 



From the standpoint of internal zooparasitism, therefore, the present public health 

 interest in rats and mice centers in trichinosis. This disease will probably never be 

 eradicated from man until rats and mice are practically eradicated, and any rational 

 public-health campaign directed against trichinosis must take the rat into serious 

 consideration. 



The eradication of rats and mice would be a very substantial contribution toward 

 a reduction and eradication of trichinosis. 



INTRODUCTION. 



From the habits of rats, it is to be expected that they harbor 

 many species of parasites, and on account of their presence in our 

 houses the question naturally arises as to whether any of these para- 

 sites are transmissible, either directly or indirectly, to man. 



The species of internal parasites which come especially into con- 

 sideration in this connection are the following: 



PROTOZOA: Chlamydophrys enchelys (p. 88), Lamblia duodenalis (p. 89), Trypanosoma 

 gambicnse (p. 94). 4 



TREMATODA: None. 



^TODA: Cysticercus cellulosx (p. 95), C. fasciolaris (p. 96), C. pisiformis (p. 95), 

 //. murina Duj. [=fraterna] (p. 96), Hymenolepis diminuta (p. 98). 



NEMATODA: Trichinella spiralis (p. 101). 



ACANTHOCEPHALA: Gigantorhynchus moniliformis (p. 108). 



ARACHNOIDEA: Linguatula denticulata (p. 110). 



Of these 11 species, the trichina worm (sometimes called the flesh 

 worm) exceeds all the others combined, both in frequency and im- 

 portance, as a cause of disease in man. 



(87) 



