The life history and development of Toxocara cati (Schrank 1788) in the domestic cat

Abstract

1. An account is given of the history, synonymy and host-range of Toxocara cati.2. Eggs of T. cati were fed to various animals, and the second-stage larvae were found in the tissues of earthworms, cockroaches, chickens, mice, dogs, lambs and cats.3. Cats were successfully infected by feeding eggs of T. cati and by feeding mice harbouring larvae in the tissues.4. In egg-infected cats the larvae were found in the liver, lungs, muscles and tracheal washings as well as in the digestive tract, indicating that they migrate through the tissues.5. In mice the larvae were found in the liver, lungs and muscles, but did not reach the alimentary tract. Changes occurred in the mouth region of the larvae in mouse tissues between 8 and 11 days after infection, but no actual moult was observed. No significant growth of the larvae was observed in mouse tissues.6. In mouse-infected cats the larvae were mostly confined to the wall and contents of the digestive tract.7. It appeared that the second moult occurred in the stomach wall of egg-infected cats at 3–10 days after infection; moulting larvae measuring 0·353–0·423 mm. in length; in a mouse-infected cat moulting larvae (length 0·459–0·765 mm.) were observed at 6 days after infection.8. In both egg- and mouse-infected cats the third-stage larvae grew in the stomach wall and moulted for the third time at a length of 0·9–1·2 mm. This occurred at about 10 days in mouse-infected cats and at about 19 days in egg-infected cats.9. The smallest fourth-stage larvae were found in the stomach contents whence they passed into the intestine. Probably they are at first attached to the wall and later become free in the intestinal contents.10. The fourth-stage larvae have lips resembling the adult; sexual differentiation occurs during this stage, being first evident at 1·5 mm.11. The fourth moult occurs in the intestine at a length of approximately 4·5–5·5 mm.12. In the adult stage the lateral alae gradually disappear and the cervical alae reach the adult form at a length of approximately 45 mm. The smallest female observed containing eggs in the vagina measured 55 mm. in length. Eggs were first observed in the faeces at 56 days after infection by eggs.13. The evidence from experimental and natural infection indicated that infection of cats with T. cati always takes place after birth.14. No larvae were found in the alimentary tract of dogs following experimental infection either with eggs or with infected mice.15. The relationship of the life history of T. cati to that of other ascaridid species, to the feeding habits of the definitive hosts, and in relation to the occurrence of human infection with this parasite is discussed.