Yesterday, we talked about how decisions are made regarding which vaccines dogs should receive. Today, I want to touch upon about a situation with horses here in Northern Colorado that shows why these recommendations are constantly being modified. (Don’t worry; we’ll talk about cats soon!)


Veterinarians in Northern Colorado used to rarely recommend vaccinating horses against rabies. We almost never saw the disease around here because the major route of transmission was through contact with bats, which is an uncommon occurrence.


This situation has changed dramatically, however. “Terrestrial” rabies (i.e., that carried by land-dwelling animals like fox, skunks, and raccoons) is now the predominant form in Northern Colorado. Experts have been watching it move in from the East and warned us about its impending arrival. Unfortunately, they weren’t mistaken.


The office of the Colorado State Veterinarian (CDA) recently sent out notifications that two horses from separate facilities in Weld County have been diagnosed with rabies. According to their reports:


On May 13th, a dead skunk was found in a horse pen on a premises near Berthoud, Colorado. The skunk subsequently tested positive for rabies. All of the horses had been rabies vaccinated by the owner approximately 1-2 years prior to the incident. A CDA Field Veterinarian examined all of the horses after the incident and no signs of trauma or bites wounds were evident. The horses were vaccinated for rabies, owners were instructed to have the horses re-vaccinated again in 30 days, and were placed under order to observe the horses closely and restrict movement for the next 120 days. On June 6th, 2013, the attending veterinarian was called to examine one of the horses which was febrile, depressed, drooling, and showing mild right facial nerve paralysis. The following day, the attending veterinarian and CDA Field Veterinarian observed that the horse showed additional clinical signs of hind limb ataxia and mild paralysis. The horse was taken to CSU Veterinary Teaching Hospital, admitted and placed in isolation. On Saturday, June 8th, the horse was euthanized and necropsied at the CSU Veterinary Diagnostic Laboratory; CSU pathologists subsequently confirmed that the horse was positive for rabies. Local public health authorities are working closely with those involved in the case for appropriate rabies prophylaxis. On June 13th, 2013, CSU Diagnostic Lab confirmatory tests revealed that another horse from Weld County was rabies-positive. The owners of the horse brought the horse to a veterinary clinic due to anorexia and colic, progressing quickly to clinical signs of stumbling, muscle tremors around the face and neck, and eventually the inability to stand. The attending veterinarian euthanized the horse and the CSU Veterinary Diagnostic Laboratory performed the testing that confirmed the horse was rabid.


When veterinarians around here (myself included) began recommending rabies vaccines for horses, many owners balked. Rabid horses just don’t fit with the picture people have of the disease, and we’ve been lucky not to see many cases in companion animals … until recently. Maybe these two tragedies will be the wake-up call we need.


Dr. Jennifer Coates


Image: makieni / via Shutterstock