Blue gill virus See American oyster reovirus

Blue River virus A strain of Sin Nombre virus in the genus Hantavirus. Isolated from Peromyscus leucopus rodents from Indiana and Oklahoma in the MidWestern USA.

Bluetongue virus (BTV) The type species of the genus Orbivirus. 24 serotypes can be identified by neutralization tests. There is a group-specific CF antigen. Causes a serious disease of sheep with a mortality of 5-30%. There is fever, edema of the head and neck, cyanosis, erosions around the mouth, sometimes pulmonary edema and lameness due to involvement of the hooves and muscle damage. Cattle and goats develop a much milder disease. Foot lesions occur in pigs. Wild ruminants are often infected. The infection is prevalent between 50° North and 30° South of the Equator. Occurs mainly in

Africa, especially in the east and south, but has occurred in Cyprus, Palestine, Turkey, Spain, Portugal, Pakistan, India, Japan and southern and western USA. The virus is transmitted by nocturnal biting flies of the genus Culicoides. Virus replication occurs in the insects but there is no evidence of transovarial transmission. Infectivity is ether-resistant. Virions have a sedimentation coefficient of 550S and contain 20% double-stranded RNA which is in 10 segments, total size 19.2kb. There are three large (3.9-2.8kb), three medium (2.0-1.8kbp) and four small (1.1-0.8kb) segments. Virions are icosahe-dral, 80nm in diameter. Unlike the Orthoreovirus, there is a diffuse outer capsid removed by exposure to CsCl. The outer coat may contain 92 capsomeres. The inner shell has a diameter of 54-64nm and contains 32 large ring-shaped cap-someres. There are seven viral proteins. Replication occurs on yolk sac inoculation of 6-day-old eggs at 33.5°C. Replication with CPE occurs in cell cultures of lamb kidney, hamster and chick embryo tissue and in BHK21 cells. An egg-attenuated vaccine is effective if polyvalent. Synonyms: ovine catarrhal fever virus; sore mouth virus.

Barber TL and Jochim MM (editors) (1985) Bluetongue and Related Orbiviruses. New York: Alan Liss

Mertens PPC and Roy P (1999) In Encyclopedia of Virology, Second edition, edited by A Granoff and RG Webster. London: Academic Press, p.1043

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