Toxoplasmosis: Current Status and Unsolved Problems. Introductory Remarks

Toxoplasma gondii was reported as a new species of protozoon in 1909. According to present knowledge, there is only one species of toxoplasma, which is pathogenic for different mammalian and avian hosts, and such names as T. cuniculi, T. canis, T. hominis, etc., are invalid. In accord with the laws of priority for binomial nomenclature, the proper name for all strains of toxoplasma is T. gondii (Nicolle and Manceaux).Although the morphology of toxoplasma is much more distinctive in stained films than in sections of fixed tissue, an unknown organism cannot be identified as T. gondii on morphology alone. The cardinal characteristics of the species are: 1. Typical morphology and staining characteristics of extracellular and intracellular forms in impression films of fresh tissue or exudate. 2. Pathogenicity for mice, guinea pigs, rabbits, chicks, etc. 3. Obligate intracellular parasitism. 4. Immunologic relationship with established strains.