马传染性贫血（沼泽热、沼泽发烧）（英文：Equine infectious anemia，简称：EIA）是在马科里的一种感染性病毒，由慢病毒属类的病毒所引起的。和人类的爱滋病属于同一种类型的病毒。通常得传染原因为血液、唾液或是身上分泌的体液等。当然也可透过吸血苍蝇感染。此病征有分为三种状况：急性、慢性和隐性。目前有Coggin's test诊断马是否有感染此病毒。感染的马类包括：家畜马、驴、斑马、骡子。此病毒并不会感染人。马传染性贫血是最早被发现的慢病毒属，但是目前也还没有可对抗的疫苗。

Equine infectious anemia or equine infectious anaemia (EIA), also known by horsemen as swamp fever, is a horse disease caused by a retrovirus and transmitted by bloodsucking insects. The virus (EIAV) is endemic in the Americas, parts of Europe, the Middle and Far East, Russia, and South Africa. The virus is a lentivirus, like human immunodeficiency virus (HIV). Like HIV, EIA can be transmitted through blood, milk, and body secretions. Transmission is primarily through biting flies, such as the horse-fly and deer-fly. The virus survives up to 4 hours in the carrier. Contaminated surgical equipment and recycled needles and syringes, and bits can transmit the disease. Mares can transmit the disease to their foals via the placenta. The risk of transmitting the disease is greatest when an infected horse is ill, as the blood levels of the virus are then highest.