Mediation of immunity to Toxoplasma gondii oocyst shedding in cats.
Immunity to Toxoplasma gondii, as measured by oocyst shedding, was studied in cats. In 3 trials, 12 3-mo-old T. gondii-free cats were fed tissue cysts of the ME-49 strain of T. gondii. All cats shed T. gondii oocysts for approximately 1 wk starting 3-5 days after ingesting tissue cysts. One cat became ill because of toxoplasmic pneumonia and was killed 17 days after inoculation. The remaining cats remained clinically normal. Approximately 3 mo after primary infection, these 11 cats (immune) and 11 age-matched or littermate uninfected cats (nonimmune) were challenged orally with tissue cysts of the ME-49 strain. In trials 1 and 3, 1 immune and 1 nonimmune cat were killed at 36 hr, 60 hr, 5 days, and 12 days after challenge and the development of T. gondii in intestines was studied histologically; in trial 2, cats were killed at 36 hr, 60 hr, and 5 days only. None of the "immune" cats shed oocysts after challenge. Asexual T. gondii types were found at 36 and 60 hr and at 5 days, indicating partial development of T. gondii in the intestine of immune cats. There were no significant differences in lymphocyte CD4+/CD8+ from spleen, popliteal, and mesenteric lymph nodes of immune cats compared to nonimmune cats.
Parasite Biology and Epidemiology Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland 20705-2350, USA.
S W
SW
Davis
J P
JP
Dubey
D000818:Animals; D015496:CD4-Positive T-Lymphocytes; D018414:CD8-Positive T-Lymphocytes; D002371:Cat Diseases / Q000276:immunology* / Q000469:parasitology; D002415:Cats; D003208:Concanavalin A / Q000494:pharmacology; D004199:Disease Vectors; D005243:Feces / Q000469:parasitology*; D007110:Immunity, Active; D007421:Intestine, Small / Q000469:parasitology; D008198:Lymph Nodes / Q000469:parasitology; D008213:Lymphocyte Activation; D051379:Mice; D010270:Parasite Egg Count; D013154:Spleen / Q000469:parasitology; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology*
D003208:Concanavalin A