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''Neospora caninum'' is a coccidian parasite that was identified as a species in 1988. Prior to this, it was misclassified as ''Toxoplasma gondii'' due to structural similarities. The genome sequence of ''Neospora caninum'' has been determined by the Wellcome Trust Sanger Institute and the University of Liverpool. ''Neospora caninum'' is an important cause of spontaneous abortion in infected livestock. ==Life cycle and transmission== ''Neospora caninum'' has a heteroxenous life cycle, with the sexually reproductive stage occurring in the intestine of a definitive host. Until recently, the only known definitive host was the domestic dog. New research has determined that other canids such as coyotes (''Canis latrans''), gray wolves (''Canis lupus''), and Australian dingos (''Canis lupus dingo'') are also definitive hosts. Oocysts passed in the feces of the definitive host, such as canines or canids, are ingested by an intermediate host, such as cattle. After ingestion of an oocyst, motile and rapidly dividing tachyzoites are released. These tachyzoites disseminate throughout the host, and in response to the host immune response, differentiate into bradyzoites, which form cysts in muscle and tissue. Formation of these cysts results in chronic infection of the intermediate host. Ingestion of infected intermediate host tissue by the definitive host completes the life cycle. A second route of transmission is the congenital transmission from mother to offspring. Transplacental transmission (passage from mother to offspring during pregnancy) has also been shown to occur in dogs, cats, sheep and cattle. If the intermediate host acquires the disease during pregnancy, it activates these cysts, and active infection often causes spontaneous abortion.〔 In addition, if the aborted fetus and membranes are then eaten by the definitive host, they cause further infection and the cycle is complete. Other carnivores, for example the red fox (''Vulpes vulpes''), may also be intermediate hosts, but they are not known to be definitive hosts. ''Neospora caninum'' does not appear to be infectious to humans. In dogs, ''Neospora caninum'' can cause neurological signs, especially in congenitally infected puppies, where it can form cysts in the central nervous system. The discovery that coyotes are definitive hosts may increase the risk of transmission of ''N. caninum'' to domestic livestock as well as to wild ruminants such as white tailed deer (''Odocoileus virginianus''). Coyote range now includes most of North and Central America.〔 Studies suggest that the parasite may be widespread among wildlife and that infection cycles cross over between wild and domestic animals.〔 Recent studies have broadened the list of known intermediate hosts to include birds. ''N. caninum'' has recently been found to infect domestic chickens and house sparrows (''Passer domesticus'') which may become infected after ingesting parasite oocysts from the soil.〔 Sparrows, which are common in urban and rural areas, may serve as a food source for wild and domestic carnivores.〔 ''N. caninum'' has also been detected in common buzzards (''Buteo buteo'') and magpies.〔 The presence of birds in cattle pastures has been correlated to higher infection rates in cattle. Birds may be an important link in the transmission of ''N. caninum'' to other animals.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Neospora caninum」の詳細全文を読む スポンサード リンク
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