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Jaagsiekte
Jaagsiekte (yaag·zeek·te) is a chronic and contagious disease of the lungs in sheep and goats first described in 1865. Its name derives from Afrikaans and means "Chasing Sickness" such that animals afflicted with the disease are in respiratory distress as if they are out of breath from being chased. It is also referred to as Ovine Pulmonary Adenocarcinoma (OPA). During end-stage disease, animals exude a foamy white fluid from the nose which is thought to be the mode of transmission between animals. Dissected lungs from afflicted sheep are interspersed with multifocal tumors. Some of these are small discrete nodules and others will involve the entire half of a lung lobule. The disease is caused by a retrovirus called the Jaagsiekte Sheep Retrovirus (JSRV) that acutely transforms the lung epithelia into cancerous cells. Specifically, Type-2 pneumocytes and club (Clara) cells of the lung are the likely target for JSRV transformation. The tumors formed there exhibit the overactive secretory functions which are a hallmark of OPA.
OPA is an infectious disease of sheep and recently has been used as an animal model for human lung cancer. It is common in the UK and in South Africa. The disease has a long incubation period and is not seen until sheep reach at least 2 years of age. Clinical symptoms include weight loss, loss of appetite, and respiratory difficulty which is associated with obvious movement of the abdomen and high pitched noises. Fluid accumulates in the respiratory tract and the disease ultimately causes death. The retroviral antigen levels of JSRV are very high in OPA tumors and can be detected in the lung secretions of infected sheep. A common field assessment for Jaagsiekte is the "wheelbarrow test" where one lifts the hind legs of the animal above the head to observe lung exudate flow out the nose and mouth. This fluid contains infectious JSRV. It is thought that infected animals secrete the virus before showing clinical symptoms and the virus is therefore easily spread within flocks. The disease is histologically similar to human bronchioalveolar carcinoma which accounts for approximately 25% of all diagnosed human lung cancers.
Dolly the sheep, the first mammal successfully cloned from an adult somatic cell, was euthanized after it was confirmed that she had Jaagsiekte.
==References==
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「Jaagsiekte」の詳細全文を読む
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