Update on the diagnosis and management of Toxoplasma gondii infection in cats.

Michael R. Lappin DVM, PhD, DACVIM
Topics in Companion Animal Medicine
Volume 25, Issue 3, August 2010, Pages 136-141

Toxoplasma gondii is a coccidian that is one of the most prevalent parasites infecting warm-blooded vertebrates around the world.1-3 Only cats complete the sexual phase in the gastrointestinal tract and pass environmentally resistant oocysts in feces. Sporozoites develop in oocysts after 1 to 5 days of exposure to oxygen and appropriate environmental temperature and humidity (Fig 1). Sporozoites can penetrate the intestinal tract of cats or intermediate hosts and disseminate in blood or lymph as tachyzoites during active infection. Toxoplasma gondii can penetrate most mammalian cells and will replicate asexually within infected cells until the cell is destroyed. If an appropriate immune response occurs, replication of tachyzoites is attenuated, and slowly dividing bradyzoites develop that persist within cysts in extra-intestinal tissues. Tissue cysts form readily in the central nervous system (CNS), muscles, and visceral organs. Live bradyzoites may persist in tissues for the life of the host.