PARASITES 371 



Aside from the above detrimental qualities, lice are undesirable because 

 of the danger of spreading disease among the animals. Their method of 

 feeding by sucking the blood of the host facilitates the spread of any organ- 

 ism living in the blood of the host. Eliot (13) has shown that P. serrata 

 transmits the blood organism Eperythrozoon coccoides. P. spinulosa of the 

 rat transmits Bartonella muris, and in rabbits, lice act as transmitting agents 

 for tularemia. 



Eradicative measures against lice must be applied directly to the mice 

 since the parasites do not commonly leave the host. Insecticides such as 

 sodium fluoride and pyrethrum, both of which are included in many com- 

 mercial products, are efTective. These may be applied by dusting the dry 

 product into the coat of the mouse, or by spraying or dipping the animal into 

 a solution of the insecticide. Spraying is more advisable than dipping, since 

 mice often become chilled following dipping and pneumonia may develop. 

 Small atomizers (perfume atomizers) can be well adapted to spraying mice. 

 Different oils including kerosene are effective, although, especially in the case 

 of kerosene, the amount applied should be limited so as not to irritate the 

 skin of the mouse. Whatever treatment is used should be repeated one or 

 two weeks after the first treatment in order to eradicate any lice which may 

 have hatched after the first application. 



Conditions which in general tend toward producing healthy mice are of 

 value in louse control. If a mouse is otherwise in good condition it usually 

 can free itself of any lice. Animals experimentally subjected to adverse 

 conditions, as being fed a deficient diet, are more commonly infested. 



Fleas 



Fleas do not tend to be as restricted to a particular host species as do 

 some of the other insect parasites. Thus, it would not be surprising to find 

 any of a number of different species of fleas attacking laboratory mice. 

 However, the species commonly known as the mouse flea is Leptopsylla 

 musculi Duges. This species occurs abundantly on mice and rats in Europe 

 and has been reported from mice and rats in the U.S. (14). The common rat 

 flea, Nosopsyllus fasciata Bosc, which is often concerned in plague transmis- 

 sion, is the flea most commonly found on rats in Europe and North America. 

 It also occurs on mice. The Oriental rat flea, Xenopsylla cheopis (Roths- 

 child), likewise well known for its role in the transmission of bubonic plague, 

 is cosmopolitan in its distribution, having established itself in several 

 localities in the Midwestern States of the United States. 



