Abstract
In our previous studies 1 on the typhus fever virus isolated from local patients, two distinct types were encountered, one simulating the classical epidemic type and the other, the endemic variety of the New World. At that time it was suggested that these two types of typhus fever might simultaneously exist in Peiping, though the popular impression hitherto was that typhus fever seen here was of the epidemic form. Recently Chung and Chang 2 studied a strain of virus isolated from a patient and identified it to be Rickettsia prowazekii, thus confirming the existence of the classical epidemic type. It occurred to us that if our contention regarding the coexistence of endemic typhus fever should be correct it would be of considerable interest to determine if local rats served as reservoir host, a fact already found to be true in the United States, Mexico, and countries surrounding the Mediterranean Sea 3 and in Manchuria. 4 This communication reports the result of study on this phase of the typhus problem.
The common house rats were collected from different households in the city, mostly from the district in which the College is located. Lots of 2 or 3 rats were killed with ether and their brains removed aseptically and emulsified in physiological saline. Half of the total suspension was injected intraperitoneally into one guinea pig. According to the usual technic employed in experimental typhus studies the body temperature of inoculated pigs was taken daily, and passage in guinea pigs was carried out with brain or blood-brain mixture of those animals showing definite elevation of temperature over 40° C. All surviving guinea pigs were kept under observation for one month and were then discarded if showing no fever.
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