If a horse comes into the hospital at this time of year and has some difficulty standing, incoordination and mild fever, the first thing on my list of likely causes is probably equine herpesvirus type I (EHV-1) infection. Next would be West Nile virus encephalitis. However, we consider all sudden onset neurological disease cases in Ontario to be rabies suspects, just in case.
Rarely is it actually rabies, which can lead to less attention to the potential for rabies infection and sometimes an approach of “we’re calling it a rabies suspect because we have to, but we really don’t think it’s a big deal.” That can lead to less care with infection control practices. However, even though it’s rare, it still happens. A recent case of rabies in a horse in Minnesota should be a reminder of that.
The scenario was similar to that described above: the horse had a hard time standing, was incoordinated, had facial spasms and a low grade fever (facial spasms would get me thinking more about West Nile since that was a pretty common sign when we saw the first wave of equine West Nile cases here in Ontario in the early 2000s). The horse was euthanized after failing to respond to treatment, was tested and was positive for rabies. Post-exposure prophylaxis (PEP) was recommended for the owner, three family members, the vet and a vet student.
As is common, a clear source of infection wasn’t identified. A skunk source is suspected because skunks are a rabies reservoir in that region, and the owner reported smelling a skunk in the area a couple months earlier (consistent with the rabies virus incubation period).
There’s no mention of whether the horse was vaccinated against rabies. I’d guess that it wasn’t, since rabies vaccine is pretty effective. While rabies is rare, this is a good reminder of the need for vaccination against this almost invariably fatal zoonotic infection, and the need to approach neurological horses with care.