Traveling horses every 3 months. Rhinopneumonitis Rhinopneumonitis in horses describes the outward signs associated with infection by equid herpesvirus types 1 and 4. However, in addition to causing abortion, this virus also causes respiratory disease and occasional paralysis. On rare occasions it can cause abortion in pregnant mares. These abortions may occur from 9 days to several months following infection.
Mares abort suddenly without signs of illness, and the fetus shows no signs of degenerative change.
At full term foals may be born alive, but if infected in utero the foals are very weak, have considerable difficulty in breathing, and invariably die from pneumonia within 48 to 72 hours. Neurological signs usually follow an earlier episode of respiratory disease or an abortion within a group of in-contact horses. Younger horses in training, repeat at 2 to 3 month intervals. All brood mares at least during 5th, 7th and 9th months of gestation. There are many types of encephalitis, and a large number of the cases are caused by viruses.