VIRAL INFECTION IN BATS 



Illation, and virus concentration in some of the tissues approached 

 the level of the stock mouse brain virus suspension used in inocu- 

 lating these animals. Virus was demonstrated in the brown fat of 

 30 per cent of the experimentally infected Myotis. These data, to- 

 gether with the recent demonstration of rabies virus in the brown 

 fat tissue in naturally infected insectivorous bats, would support the 

 h)T)othesis that this tissue provides nutriment for a latent focus of 

 infection (Bell and Moore, 1960 ;Sulkin, 1962), Studies are in progress 

 to determine the frequency with which virus can be demonstrated, 

 under natural conditions, in the brown adipose tissue of bats netted 

 in different geographic areas at different times of the year. 



The mechanism by which brown fat may actually serve as a depot 

 for storage of rabies virus is still under study, A working hypothe- 

 sis concerns the possibility that at least in hibernating species, 

 rabies virus sequesters in brown adipose tissue in the quiescent 

 host during the period of hibernation and is subsequently activated 

 by the physiological alterations which occur prior to awakening and 

 by emergenceintoawarmer environment. Studies concerned with the 

 effect of low environmental temperature on the pathogenesis of ra- 

 bies in insectivorous bats would suggest that this may actually be 

 the case. The remaining portion of this discussion will be limited 

 to those areas which relate to the subject of this conference. 



It is clear from previous discussions in this conference that en- 

 vironmental temperature has been shown to have a significant effect 

 on several experimental virus-host systems, both in vivo and in 

 vitro. It is also apparent that the outcome of such experiments de- 

 pends on the particular virus used and on the host or cell system 

 under study (Sulkin, 1945; Walker and Boring, 1958; Hoggan and 

 Roizman, 1959; Lwoff, 1959). 



During the course of studies on the role of Chiroptera as reser- 

 voir hosts for viruses innature,itbecame evident that these exper- 

 iments with bats provided an unusual opportunity for determining the 

 effect of temperature on viral multiplication in the intact animal. 

 The bat does not possess a thermoregulatory mechanism for main- 

 taining a constant normal body temperature, but rather, the body 

 temperature of a bat is that of his environmnet, except when he is in 

 the active state of walking or flying (Hock, 1951; Morrison, 1959), 



373 



