bornavirus

noun

bor·​na·​vi·​rus ˌbȯr-nə-ˈvī-rəs 

variants or borna virus or borna disease virus

: a single-stranded RNA virus (family Bornaviridae) that has a spherical virion with a lipoprotein envelope and chiefly infects the central nervous system of birds and mammals (such as sheep, dogs, and horses) causing mild to fatal disease

Bornaviruses, a group of RNA viruses that cause disease in horses and sheep, first inserted their genetic material into ancestral human DNA at least 40 million years ago …

—Tina Hesman Saey, Science News