Toxoplasivli Gondii Oocyst from Cat Feces

Toxoplasma infect ion is c o m m o n in m a n and animals, ye t for 60 years the life cycle of Toxoplasma gondii remained unknown. Recen t ly a new form of Toxoplasma was found in the feces of cats t ha t had ea ten Toxoplasma-infected mice (for rev iew of earlier work see [1]). Th is fecal form is biological ly different f rom the known stages of Toxoplasma. While searching the feces of cats for a morphological equ iva len t of Toxoplasma, several cand ida te forms such as fungi, cysts of flagellates, and coccidian oocysts resembling those of Isospora fells, I. rivolta, and I. bigemina were found. Of these only oocysts resembl ing [. bigemina were cons tan t ly and q u a n t i t a t i v e l y associated wi th fecal Toxoplasma infect ivi ty. We will describe and character ize these oocysts and show by a series of m u t u a l l y independen t de te rmina t ions tha t t hey should be regarded as oocys ts of Toxoplasma got~dii. Some of these findings were briefly repor ted (2).