is a coccidian parasite of animals. as a serious disease of cattle and dogs worldwide. Additionally clinical neosporosis has been reported in sheep goats deer a rhinocerus and horses and antibodies to have been JNJ7777120 found in the sera of water TCL1B buffaloes red and gray foxes coyotes and camels and felids. BIOLOGY Life Cycle Dogs are both the intermediate and definitive host for (McAllister et al. 1998 Lindsay et al. 1999 1990 2001 Basso et al. 2001 Dubey et al. 2002 The life cycle is typified by 3 infectious stages: tachyzoites tissue cysts and oocysts (Fig. 1 and Fig. 2). Tachyzoites and tissue cysts are the stages found in the intermediate hosts and they occur intracellularly (Dubey et al. 2002 Tachyzoites are approximately 6 × 2 μm (Fig. 1). Tissue cysts are often round or JNJ7777120 oval in shape up to 107 μm long and are found primarily in the central nervous system (CNS). The tissue cyst wall is up to 4 μm thick and the enclosed bradyzoites are JNJ7777120 7-8 × 2 μm. Thin-walled (0.3-1.0 μm) tissue cysts have been recently reported in muscles of cattle and dogs naturally-infected with a stages in dogs. Bar = 20 μm and applies to all figures. (A) Tachyzoites in an impression smear of lung. Giemsa stain. Note individual organisms (arrowheads) and those dividing into 2 (arrows). Compare size with red blood cells … Domestic dogs are the only known definitive host for unsporulated oocysts from experimentally-infected dogs were 11.7 × 11.3 (10.6-12.4 × 10.6-12.0) μm in size (Lindsay et al. 1999 oocysts sporulate outside the host. oocysts are morphologically similar to and oocysts in cat feces and broadly resemble oocysts of in animals using the natural routes of transmission. The parasite can be transmitted transplacentally in several hosts and vertical route is the JNJ7777120 major mode of its transmission in cattle. Carnivores can acquire infection by ingestion of infected tissues (McAllister et al. 1998 Lindsay et al. 1999 1999 Dijkstra et al. 2001; Schares et al. 2001 Gondim et al. 2002 It is epidemiologically important to be able to identify oocysts in dog feces. Microscopic examination alone will not be enough to identify oocysts in dog feces. Methods have also been developed to genetically distinguish oocysts from oocysts (Hill et al. 2001 ?lapeta et al. 2002 oocysts have been identified feces of only two naturally-infected dogs (Basso et al. 2001 ?lapeta et al. 2002 Animal models There are no suitable animal models at the JNJ7777120 present to perform bioassay to detect oocysts in dog feces. Although interferon-gamma gene knockout (KO) mice are highly susceptible to parenteral inoculation with tachyzoites and tissue cysts (Dubey and Lindsay 1996 Dubey et al. 1998 they are less susceptible to parenteral or oral inoculation with oocysts. Gerbils (infection with oocysts (Dubey and Lindsay 2000 Basso et al. 2001 Schares et al. 2001 Another species of gerbils and sand rats (because of previous experience with the related parasite and are very closely related parasites structurally genetically and immunologically caution should be used in making generalizations about based on the biology of because neosporosis and toxoplasmosis are biologically distinct diseases. is a major disease of sheep and humans and not of cattle whereas neosporosis is a major disease in cattle not of sheep and there is no evidence for human infection. NEOSPOROSIS IN CATTLE Bovine neosporosis has been reviewed in several papers (Dubey and Lindsay 1996 Wouda 1998 Dubey 1999 Anderson et al. 2000 Buxton et al. 2002 Dijkstra 2002 Innes et al. 2002 Jenkins et al. 2002 Dubey 2003 Therefore most references on bovine neosporosis were omitted from this review. Clinical signs causes abortion both dairy and beef cattle. Cows of any age may abort from 3 month gestation to term. Most neosporosis-induced abortions occur at 5-6 month gestation. Fetuses may die in utero be resorbed mummified autolyzed stillborn born alive with clinical signs or born clinically normal but chronically infected. Neosporosis-induced abortions occur year-round. Cows with antibodies (seropositive) are more likely to abort than seronegative cows and this applies to both dairy and beef cattle. However up to 95% of calves born.