Resistance of Leishmania cultures to cold

Abstract

On the assumption that Leishmania is able to persist outside the vertebrate host, it is evident that in North China the parasite must be capable of with-standing exposure to extreme cold, for during the winter the temperature in Shantung Province often reaches — 20° C. If the parasite is able to persist throughout the winter in the body of some insect, the flagellate stage should not be killed by exposure to low temperatures. So far as we are aware, no observations have hitherto been recorded on the resistance of flagellates to cold, and, therefore, we examined a number of hibernating insects with a view to finding out whether natural flagellates could persist during the winter. Active flagellates were found in the alimentary tract of hibernating females of Culex fatigans , and in a Pentatomid bug caught in January, and also in the same species of bug in March, after it had just emerged from hibernating during the winter, thus showing that natural flagellates of these insects are not affected by cold. In addition, experiments were made with cultures of Leishmania , in order to determine whether the flagellate stage of this parasite was equally resistant to cold.