STUDIES ON THE IN VITRO AXENIC DEVELOPMENT OF TRICHINELLA SPIRALIS: I. BASIC CULTURE TECHNIQUES, PATTERN OF DEVELOPMENT, AND THE EFFECTS OF THE GASEOUS PHASE

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Abstract
Trichinella spiralis larvae from rat muscles were cultured axenically in roller tubes. In chick embryo extract and rabbit serum medium, male and female external genitalia appeared after the second incomplete molt. Molting was preceded by cuticular swelling around the neck, followed by constriction and ultimate rupture. The worms did not increase in size. Digestive enzymes and bile salts did not promote exsheathment and were often toxic. With added vitamins, the second molt was reached after 24 hours in vitro (as against 48 hours in the basic medium), but amino acids and glucose had no effect on survival and development. Under nitrogen or 5% CO2 in nitrogen the worms survived longer than in the presence of 5% oxygen or under air. Development was better in the presence of 5% CO2 than under 5% oxygen, and still better under higher CO2 tensions. Because CO2 tension in the mammalian intestine is often high, this gas and (or) carbonic acid probably play an important part in the biology of intestinal parasites. The two incomplete molts represent advancement through two stages and the worms with external genitalia are believed to be immature adults (that is, fifth stage). Because direct microscopic evidence of molting prior to encapsulation in muscles of infected animals has been obtained, the infective larvae are believed to be in the third stage.