A satisfactory technique for storing and staining malaria and other parasites in old blood films

Abstract

1. 1) Unstained and unfixed thick and thin blood films stored in a desiccator in a refrigerator for at least 3 years can be stained by a method which gives results quite as good as those stained with films prepared and stained on the same day. 2. 2) Giemsa stain diluted with a physiological salt solution gives better results than does Giemsa stain diluted with distilled water. 3. 3) Autofixation soon occurs in thick blood films which are exposed to atmospheric conditions, especially in hot climates and the higher the temperature the more quickly this occurs. This prevents haemolysis and subsequent satisfactory staining. 4. 4) Thick blood films which are stored in a desiccator for years dehaemoglobinize within 2 or 3 minutes when they are exposed to water, and in less than a minute when soaked in saline (0.8 per cent. sodium chloride). 5. 5) Better staining results are obtained with Giemsa saline (1–10) than by all the other Romanowsky modifications we have tested. However, Giemsa diluted with distilled water and Leishman's and Wright's stains give good results. 6. 6) Thick and thin films stain badly when exposed to the air even for a few weeks. If old films must on occasion be stained, a watery stain (Giemsa) should always be used and thin films should not be fixed before staining. Thick films exposed to the air for 3 years are quite unstainable, but in thin films the parasites are just recognizable.