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==Description==

==Description==

Equine Infectious Anaemia (EIA) is an exotic viral disease affecting horses, donkeys and mules characterised by immuned-mediated haemolytic anemia. It is caused by Equine Infectious Anaemia Virus (EIAV), an equid-specific lentivirus in the retrovirus family that is closely to related to HIV in humans. EIA occurs in acute and subacute forms in susceptible horses but more commonly assumes a chronic course. Affected horses that recover from EIA may become lifelong carriers, and relapse of the disease may occur during times of stress or illness.

Equine Infectious Anaemia (EIA) is an exotic viral disease affecting horses, donkeys and mules. It is caused by Equine Infectious Anaemia Virus (EIAV), an equid-specific lentivirus in the retrovirus family that is closely to related to HIV in humans. EIA occurs in acute and subacute forms in susceptible animals but more commonly assumes a chronic course. Affected horses that recover from EIA may become lifelong carriers, and relapse of the disease may occur during times of stress or illness.

Cases of EIA in the UK are extremely rare and have previously occurred in horses that have travelled abroad or have been imported from areas of endemic disease.

Cases of EIA in the UK are extremely rare and have previously occurred in horses that have travelled abroad or have been imported from areas of endemic disease. The disease is notifiable and confirmed cases must be humanely destroyed.

==Signalment==

==Signalment==

==Pathogenesis==

==Pathogenesis==

EIA occurs worldwide but most commonly in countries with warm climates. The virus is usually transmitted via mechanical innoculation of blood from large biting flies such as horseflies (''Tabanid'' spp) or stable flies (''Stomoxys calcitrans''). Transmission of the virus can also occur through saliva, milk, body secretions or via contaminated needles and blood products.

EIA occurs worldwide but most commonly in countries with warm climates. The virus is usually transmitted via mechanical innoculation of blood from large biting flies such as horseflies (''Tabanid'' spp) or stable flies (''Stomoxys calcitrans''). Transmission of the virus can also occur through saliva, milk, body secretions or via contaminated needles and blood products. The disease may be passed from pregnant mares to their foals across the placenta.

Following coating of erthrocytes and thrombocytes by the virus and the development of a Type III immune complex reacion, lysis of erthrocytes occur. Infection with EIA results in an acute phase of infection followed by recurrent episodes that usually susbide after a period of time. Affected horses become persistently infected, lifelong carriers of the disease due to latent infection of macrophages. EIA may be induced by stress, disease or immunosuppressive drugs.

Following coating of erthrocytes and thrombocytes by the virus and the development of a Type III immune complex reacion, lysis of erthrocytes occur. Infection with EIA results in an acute phase of infection followed by recurrent episodes that usually susbide after a period of time. Affected horses become persistently infected, lifelong carriers of the disease due to latent infection of macrophages. EIA may be induced by stress, disease or immunosuppressive drugs.