Experiments bearing on the susceptibility of the striped hamster ( Cricetulus griseus ) to Leishmania of Chinese Kala Azar

The experimental study of Kala Azar has been greatly facilitated by the introduction of the use of the Chinese striped hamster (C. griseus) as a laboratory animal. Smyly and Young (1924) were the first to demonstrate the marked susceptibility of this animal to infection with Leishmania, and subsequently, in collaboration with Brown (Young, Smyly and Brown, 1926), they confirmed and extended their original observations. Utilizing large numbers of hamsters, they were able to show that the intraperitoneal route is the most certain method of infecting this rodent. Out of a total of 182 hamsters inoculated in this way, 129 were positive after intervals varying from 10 to 347 days; and they noted that the parasites originally inoculated into the peritoneum could persist there for about a month after they were introduced. Two hamsters were infected by intrapleural injection, and both became infected, one after 15 days, and the other after an interval of 67 days. The infection in each case was detected by liver puncture. With regard to subcutaneous injection of the parasites into hamsters, these authors only succeeded in infecting three hamsters out of a total of 14. In connection with all their experiments it should be noted that their animals were invariably inoculated with relatively large quantities of liver and splenic emulsion, rich in parasites. It is important to note that in spite of the fact that large numbers of parasites were usually present in the spleen and liver, and the former organ was greatly enlarged, the animals seemed to remain in good health for long periods; although no tendency to spontaneous recovery was ever observed.