36o BIOLOGY OF THE LABORATORY MOUSE 



Taenia taeniaeformis (batsch, 1786). — Also known as T. crassicollis. 

 This is a tapeworm which commonly employs the mouse or rat as an inter- 

 mediate host. The larval stage, which bears the name Cysticercus fasciolaris , 

 is a strobilocercus (Fig. 140). It develops within a cyst in the liver of the 

 mouse or rat. The adult is a very common tapeworm of the intestine of the 

 domestic cat having also been reported from wild cats (Fig. 141). 



Infection in mice is effected by ingesting the eggs. In the intestine the 

 shells are digested off, liberating the onchospheres which penetrate the wall 

 of the intestine and make their way to the liver via the hepatic portal system. 

 On the second day after ingestion of the egg the onchosphere 

 has reached the capillaries of the liver. A cyst wall forms 

 around the larva which develops into the strobilocercus 

 lying free within the cyst bathed in a clear, yellowish fluid. 

 Cats become infected by ingesting infected mouse or rat 

 livers. 

 ii This is an especially interesting parasite in that from 



Pj(j J.J the walls of the cysts sarcomata of the liver develop. 



Scolex of Taenia Bullock and Curtis (7) in 1920 reported producing 

 taeniaeformis cysticercus tumors in some 201 rats by feeding them the 

 (X15). {From gggg Qf ^]^g parasite. Later it was used extensively in 

 a . a] er eu- ^^^^qj. experiments, especially by Dunning and Curtis (12). 

 wan.) II' 1 • T 1 • 



Except when bemg used m tumor studies, this parasite 



quite obviously would be very undesirable in laboratory mice. However, 

 control measures are not difficult, for if the primary hosts, i.e., cats, are 

 eliminated from the laboratory, the main source of infection is removed. 

 If it is desirable to have a cat around the building, as sometimes one proves 

 quite indispensable in keeping down wild mice, the cat should not have access 

 to the feed room or be permitted to climb over the feed or bedding at any 

 time. Periodic examination and treatment of infected cats constitutes a 

 control measure of value for preventing infection in mice. 



Taenia pisiformis (block, 1780). — This is a common tapeworm of dogs 

 and is occasionally found in cats. The larva is a cysticercus (Cysticercus 

 pisiformis) which develops in the liver and mesenteries of the rabbit and has 

 been reported from the mouse. However, the paucity of the records of the 

 cysticercus occurring in the mouse minimizes the prospects of its becoming a 

 pest among laboratory mice. For a rather complete account of its develop- 

 ment see Hegner, Root, Augustine, and Huff, Parasitology, page 318 (20). 



Hymenolepis fraterna (stiles, 1906). — Many authors apply the name 

 U.fraterna to the common "dwarf tapeworm" of the mouse and rat, thus 



