SUMMARY 



that host resistance to selected strains and doses of salmonella and 

 staphylococci was decreased by a low environmental temperature. 

 Dr. Metcalf and Dr. Walker demonstrated that in chilled animals 

 there is a lowered resistance to influenza and Coxsackie B-1 viruses 

 respectively. And Dr. Marcus has shown us that chilled mice which 

 were not acclimatized are more susceptible to Coxsackie B- 5 virus 

 than are normal animals. On the other hand, Dr. Sulkin has told us 

 that there is less rabies or encephalitis virus produced in bats at 

 -2° C than at higher temperatures. These findings clearly indicate 

 the complexnatureoftheproblemsweface.lt is indeed logical to ex- 

 pect less virus production in cells whose metabolism is lowered by 

 cold; but pathogen replication is only one phase of disease produc- 

 tion, although it is an important one. 



Another aspect of these experiments conducted with animals is 

 that it became clear that in challengingthem while kept at normal or 

 low ambient temperatures, one must define certain experimental 

 procedures quite carefully. These include such aspects as ambient 

 temperature, rectal temperature, cage type, bedding (or lack of 

 bedding), acclimatization (which should be defined by physiological 

 measurements, if possible), virulence and dosage of pathogen, and 

 site of inoculation (S. C, or I. P. being the major methods used). 



Dr. Walker's report on virus replication showed that the strain of 

 Coxsackie used was replicated in the pancreas of animals kept at 

 normal temperatures, but was not replicated in other tissues. In- 

 fections of the pancreas are rare, yet this strain of Coxsackie 

 selects this organ as its site of operations in the normal animal. 

 When the animals were chilled in Dr. Walker's experiments, the 

 virus became replicated in many tissues. 



Dr. Berry cited Shephard's success in producing growth of M. 

 leprae in mice injected in the foot pad, and Shephard has surmised 

 that success was based on the lower temperatures of foot pad tissue. 

 We all know that T. pallida will not infect rabbit testicles unless the 

 ambient temperature is lower than 59.5° C. Also, elevated body 

 temperatures have been used in man to treat s3T3hilis. One wonders 

 if these effects are related to the metabolism of the pathogen or 

 host defense mechanisms. It is of some interest to observe that cer- 

 tain pathogens such as the trypanosomes and leptospira grow much 



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