The recent Kentucky Derby featured superbly athletic horses at the prime of their lives. Unfortunately, not all horses (or other livestock for that matter) are so fortunate. In the past week, 2 stories have been hoofing around the news. The first has been an outbreak of vesicular stomatitis virus, a rhabdovirus like the infamous rabies. It primarily infects insects and livestock, but it can be a zoonotic disease of humans that consists of flu-like symptoms. VSV has also been studied as a candidate for virus-based vaccine therapy (http://wwwnc.cdc.gov/eid/article/21/2/14-1649_article).
In Kane County, Utah, several horses and a mule have become sick with VSV. While many animals recover from vesicular stomatitis, it can cause lesions in the animals’ mouths and on their hooves that cause them pain. It also causes them to show a severe decrease in appetite, which is especially problematic for dairy cows and other animals who are supposed to grow fast and/or be in good physical condition. While the exact means of transmission isn’t known, it is thought that saliva and fluid from ruptured blisters are a likely mechanism. Seeing as rabies is also transmitted via saliva, this seems plausible.
In Oregon, four horses have tested positive for equine herpes virus (EHV-1). Herpesviridae, as we’ve learned, is a very old and successful group of viruses that infect a myriad of different species. These viruses can cause a wide variety of symptoms (remember the 9 human herpes viruses?).
Like all herpesviruses, it can go latent and then reactivate to cause clinical disease. Horses infected with EHV-1 can suffer from respiratory and neurologic symptoms (e.g. loss of muscle tone), as well as fever, urine dribbling and nasal discharge. In severe cases, the animal may die, or a pregnant mare may abort her fetus. The symptoms are treatable, but as is the case with human herpes viruses, “unlike love, herpes is 4ever”™. While humans aren’t in any danger from the virus, they can spread it on their clothing and equipment.