MICROBIOLOGICAL ASPECTS OF HIBERNATION 

 IN GROUND SQUIRRELS 



J. Schmidt 



Department of Bacteriology 



University of New Hampshire 



Durham, New Hampshire 



ABSTKAGT 



Studies were designed to determine the effect of reduced temperatures on the normal 

 bacterial and viral flora of the experimental animals and on the fate of other micro- 

 organisms artificially introduced. Determinations were made of the number of coliform 

 bacilli, fecal streptococci, and psychrophilic organisms present in the fecal material 

 before and immediately after hibernation. In addition, the total viable aerobic cell 

 count was determined. All counts were based on the number of orgamsms per gram 

 (dry weight) of fecal materal. The data indicate a gradual 3 log increase in the number 

 of psychrophiles and a simultaneous decrease of similar magnitude in the number of 

 coliform bacilli during periods of hibernation. No change which could be associated with 

 hibernation was noted in either the total cell count or the number of fecal streptococci. 

 The animals were shown to be free of viruses capable of inducing a cytopathogenic 

 effect in monolayers of either HeLa, human amnion, or monkey kidney cells. Fecal 

 samples from each of 32 animals were repeatedly tested over a period of four months. 

 Bacterial viruses ( Escherichia coli phage) have been demonstrated in only one of the 

 40 ground squirrels examined. Several strains of E. coli isolated from the animals were 

 used as the host cell in the test systems. The effect of hibernation on the presence of 

 artificially introduced ECHO-6 and Coxsackie B-3 viruses and E. coli phage in the in- 

 testinal tract of ground squirrels is being evaluated. 



Hibernating mammals provide an excellent means for studying 

 the effect of cold on the biology of experimental infection from the 

 standpoint of boththehostand the parasite. These animals represent 

 a unique situation in which a normal system is available in the same 

 species, at widely separated temperatures. For instance, in the ac- 

 tive state a ground squirrel has a normal body temperature of ap- 

 proximately 37° C, whereas in hibernation its normal temperature 

 may approach 0° C. 



The studies reported here deal with the effect of hibernation on 



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