Detection of Toxoplasma cysts and oocysts in an urban environment in a developed country.
Feces of 115 stray or unwanted cats were screened for Toxoplasma oocysts by sucrose density centrifugation and inoculation into mice. None of the feces examined contained detectable levels of viable oocysts. Using a laboratory infected cat, the sensitivity of this detection technique was found to be about 250 oocysts/g of feces by microscopic analysis and about 2 oocysts by mouse inoculation. Samples of pork and lamb chops bought from suburban butcher shops were screened for Toxoplasma cysts by pepsin digestion and mouse inoculation. One of the 30 pork and none of the 30 lamb chops contained viable cysts. Experimental studies determined that the sensitivity of this method of detection was about 1 cyst/100 g of tissue. The relative likelihood of each route of Toxoplasma infection for members of an urban community in a developed country is discussed.