Viability of Sarcocystis neurona sporocysts and dose titration in gamma-interferon knockout mice

Gamma-interferon knockout mice have become the model animal used for studie s on Sarcocystis neurona. In order to determine the viability of S. neurona sporocysts and to evaluate the course of the disease in these mice, sporoc ysts were collected from opossums (Didelphis virginiana), processed, and st ored fur varying periods of time. Gamma-interferon knockout mice were then inoculated orally with different isolates at different doses. These animals were observed daily for clinical signs until they died or it appeared nece ssary to humanely euthanize them. 15 of 17 (88%) mice died or showed clinic al signs consistent with neurologic disease. The clinical neurologic sympto ms observed in these mice appeared to be similar to those observed in horse s. 15 of 17 (88%) mice were euthanized or dead by day 35 and organisms were observed in the brains of 13 of 17 (77%) mice. Dose appeared not to effect , clinical signs, but did effect the amount of time in which the course of disease was completed with some isolates. The minimum effective dose in thi s study was 500 orally inoculated sporocysts. Efforts to titrate to smaller doses were not attempted, Direct correlation can be made between molecular ly characterized S. neurona sporocysts and their ability to cause neurologi c disease in gamma-interferon knockout mice. (C) 2001 Elsevier Science B.V. All rights reserved.