VIRAL INFECTION IN BATS 



identical with their winter hibernation, and serves to emphasize the 

 necessity for carrjdng out low temperature studies in bats gathered 

 during the fall months. 



Table II summarizes a study of the suppressive effect of simu- 

 lated hibernation on the susceptibility of little brown bats to two 

 strains of rabies virus. Of those receiving the canine rabies virus 

 (Thompson) and placed in the cold room,infection was demonstrated 

 in only 7.5 per cent of 40 bats studied over 40 days. The infection 

 rate amor^ animals kept at 29° C was 36 per cent, and virus was 

 demonstrated between the ninth and thirtieth day following virus in- 

 oculation. It is interesting that virus was demonstrated more fre- 

 quently in the brown adipose tissue (25.7 per cent) than in the sali- 

 vary gland (11.4 per cent). The infection rate was even higher among 

 animals held in the cold for two weeks and then transferred to the 

 warm room. Again virus was demonstrated more frequently in the 

 brown fat (30.4 per cent) than in the salivary gland (17.1 per cent). 

 Quantitative data not shown in this tabulation indicate that virus ti- 

 ters in the few animals which developed evidence of infection while 

 in simulated hibernation were 10"^^ or less, while titers in various 

 tissues of animals in the warm room ranged from one log unit to as 

 high as 10"'^^. In the experiment with the rabies virus (59V13B) re- 

 covered from the pooled brown adipose tissue of naturally infected 

 little brown bats,virus wasagaindemonstratedinfequentlyintissues 

 of animals inoculated and placed directly in the cold room, but re- 

 mained viable and was activated when animals were transferred to 

 the warm room.Although the infection rates were similar with both 

 rabies virus strains, a careful study of the results revealed differ- 

 ences in the patterns of infection produced by these viruses in active 

 bats and in those awakened foUowir^ a period in simulated hiberna- 

 tion.The bat rabies virus occurred more frequently in the brown adi- 

 pose tissue than in either salivary gland or brain,It can be seen that 

 virus was detectable in the interscapular brown fat in 92 per cent 

 of animals shown to develop infection, and inthe salivary gland and 

 brain in only 28 per cent and 50 per cent respectively. Rabies in- 

 f6ction was demonstrated in 42 per cent of the animals held in the 

 cold for 17 days before transfer to the warm room, and the infection 

 pattern seemed to be affected by the period in simulated hibernation. 

 In these animals virus was demonstrated in the brown fat, salivary 

 gland, and brain of infected animals with about equal frequency. 



375 



