Coccidians

Toxoplasma gondii. Oocysts in formalin-preserved wet mount preparation of cat feces (unstained, high power). Oocysts of T. gondii occur naturally only in the feces of cats or other felids that serve as definitive hosts for this parasite; they do not occur in human feces. They are shown here because not infrequently individuals who are concerned about cats as a source of human toxoplasmosis submit fecal specimens from their pet cats for examination. Oocysts are unsporulated when excreted in cat feces and usually require 48 to 74 hours to undergo sporulation in the external environment. In this field, sporulated oocysts contain two sporocysts, each of which contains four sporozoites.