SULKIN AND ALLEN 



determine the degree of susceptibility of various species to certain 

 virus strains and to locate the tissues involved in the infection which 

 provided sites for viral proliferation and resultant viremia. Again, 

 emphasis was placed on determining if virus invaded and multiplied 

 in interscapular brown adipose tissue, thereby providing a mecha- 

 nism for survival of arbovirus particles in the hibernating animal 

 in a manner similar to that described for rabies virus. 



In the initial experiments (SulMn, Allen and Sims, 1960), we were 

 able to confirm certain aspects of the observations reported by 

 Corristan et al. (1956) and LaMotte (1958), Viremia was demon- 

 strated in bats following peripheral inoculation of Japanese B or 

 St. Louis encephalitis viruses and, in addition, the lipotropic char- 

 acteristic of these viruses was demonstrated. These experiments 

 have now been extended to include various bat species and several 

 virus strains. Bats were inoculated subcutaneous ly and placed in 

 specially designed cages which allowed them to receive fresh food 

 and water daily with nimimum danger to the caretakers. The virus 

 inoculum consisted of approximately 150 weanling mouse i.e. LD-^ 

 of mouse brain suspension, or infected tissue culture fluid, or bat 

 blood. To simulate natural circumstances, bats were kept in near 

 darkness throughout the day and were offered food at the close of 

 each working day. Unless otherwise indicated, animals were main- 

 tained at 24° C * 2° C (relative humidity 65 per cent) and were ob- 

 served several times daily throughoutthe course of the experiments 

 for possible signs and symptoms of encephalitis. When tissues were 

 obtained for virus assay, extreme care was taken to rid specimens 

 of as much blood as possible so that resulting virus titers would re- 

 flect virus multiplication in a specific tissue and not virus present 

 in blood circulating through that tissue. These experiments, which 

 will be published in detail elsewhere (Sulkin, Allen and Sims, un- 

 published data), indicate that the Mexican free- tailed bat is only 

 slightly susceptible to the high mouse passage Nakayama strain of 

 Japanese B encephalitis virus, but is significantly more susceptible 

 to a mosquito isolate (OCT- 541) which had been through two hamster 

 kidney tissue culture passages and one passage in little brown 

 Myotis. In the latter case, the infection was widely disseminated in 

 animals sacrificed over a period of 3 weeks, with virus concentra- 

 tions reaching 3 logs or more inblood, brown fat, and kidney. In one 

 instance virus was demonstrated in the brown fat and not in the 



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