VIRAL INFECTION IN BATS 



quitoes present at the hibernating site. In this regard, it is of in- 

 terest that LaMotte (1958) has shown that mosquitoes will feed on 

 bats at 10° C. Thus the viremic, hibernating bat could provide a mid- 

 winter feeding of infected blood for mosquitoes, making possible a 

 two-step winter transmission chain as suggested by Bellamy, Reeves 

 and Scrivani (1958) for western equine encephalitis virus in birds 

 and mosquitoes. In addition, the bat which enters hibernation in a 

 viremic state, although his blood titer gradually decreases during 

 the winter, would be capable of circulating virus again upon arousal 

 in the spring) and (3) bats which enter hibernation at a time when 

 they possess neutralizing antibodies against Japanese B encephalitis 

 virus may show negative neutralization indices by the termination 

 of their winter sleep and the warmer environmental temperature, 

 together with the physiological alterations which occur at time of 

 arousal and emergence, could serve to activate latent Japanese 

 encephalitis virus infection and produce viremic hosts without the 

 necessity of re- infection. 



We feel that these studies demonstrating experimentally the var- 

 ious conditions under which the hibernating bat can serve to over- 

 winter an arbovirus add strong supportive evidence to the growing 

 concept of the role of hibernating animals inthe maintenance of these 

 agents in nature during periods when vectors are not active. Another 

 hibernating mammal, the hedgehog, has been shown experimentally 

 to circulate Russian spring- summer encephalitis virus during 

 periods in the cold (van Tongeren, 1958) and experimental studies 

 with western equine encephalitis virus in snakes (Thomas and Ek- 

 lund, 1960) and Japanese B encephalitis in frogs (Chang, 1958) sug- 

 gest that these poikLlothermic animals may be capable of overwin- 

 tering these viruses. 



In addition to the broad epidemiological aspects of the studies 

 presented here, the compiled data also provide information of a 

 more fundamental nature relative to the influence of temperature on 

 the virus-cell-host relationship per se. There is no doubt that the 

 multiplication rate of both rabies and Japanese B encephalitis 

 viruses is suppressed in the bat by maintaining the animal at low 

 temperature. The manner in which infection with both these agents 

 is sustained for long periods of time in the dormant animal, however, 

 suggests that some type of viral activity occurs in this host at low 



389 



