Experimental transmission of Sarcocystis speeri Dubey and Lindsay, 1999 from the South American opossum (Didelphis albiventris) to the North Americanopossum (Didelphis virginiana)

Sarcocystis speeri Dubey and Lindsay, 1999 from the South American opossum Didelphis albiventris was successfully transmitted to the North American op ossum Didelphis I . Sporocysts from a naturally infected D. albiventris fro m Argentina were fed to 2 gamma-interferon knockout (KO) mice. The mice wer e killed 64 and 71 days after sporocyst feeding (DAF). Muscles containing s arcocysts from the KO mouse killed 71 DAF were fed to a captive D. virginia na; this opossum shed sporocysts 11 days after investing sarcocysts. Sporoc ysts from D. virginiana were fed to 9 KO mice and 4 budgerigars (Melopsitta cus undulatus). Schizonts, sarcocysts, or both of S. speeri were found in t issues of all 7 KO mice killed 29-85 DAF: 2 mice died 39 and 48 DAF were no t necropsied. Sarcocystis stages were not found in tissues of the 4 budgeri gars fed S. speeri sporocysts and killed 35 DAF These results indicate that S. speeri is distinct from Sarcocystis falcatula and Sarcocystis neurona, and that S. speeri is present in both D. albivntris and D. virginiana.