Rabies On The Rise
Written by: Dr. Allen Landes
Rabies is a disease that strikes fear into the hearts of people and conjures up thoughts of the book and movie "Old Yeller". Since the advent of the first vaccine by Edward Jenner in the 1700's, rabies became one of the first diseases that a vaccine was developed in an attempt to eradicate its existence. This was due to its potential to infect humans and the deadly nature of the infection. In 1885 Louis Pasteur and Emile Roux developed the first rabies vaccine and the number of rabies cases seen in the United States dropped dramatically.
Rabies is an uncommonly encountered neurologic disease of horses. While the incidence of rabies in horses is low, the disease is invariably fatal and has considerable public health significance. The rabies virus attacks the nervous system and eventually travels its way to the brain of the infected animal. From the brain the infection travels to the animal's salivary ducts. The infected animal then passes on the virus to its victim, human or animal through its saliva. The rabies virus infects an animal or human by entering the body of the victim from the saliva of the infected (rabid) animal. The usual way we think of this happening is from the bite of a rabid dog. But infection can be from contact with the saliva of rabid animals to cuts, or abrasions on one's hands, or from contact of saliva to mucous membranes, i.e. mouth or eyes. The rabies virus can infect all mammals worldwide, but in the United States the wild animals most likely to be infected with the virus are skunks, coyotes, foxes, raccoons, and bats. The key symptoms are hyper-salivation, behavioral changes, increased sensitivity at the site of the injury, low grade fever, lameness, and anorexia. The key to these symptoms are that they progress rapidly in 5-7days and ends in recumbency and death.
The prevalence of rabies in Colorado is on the increase. As of May of this year, there was a report from the State Veterinarian's office that there has been a significant rise in the number of terrestrial rabies in eastern Colorado. The increased numbers of rabies cases has come from skunks. There has been a steady level of bat rabies cases in Colorado for the past 10 years ranging from 32 confirmed cases in 2001 to 70 confirmed cases in 2006. In 2007 there were 4 skunk rabies cases, 1 coyote positive for rabies and in 2008 as of October 2; already there are 18 confirmed cases of skunk rabies in Colorado.
Earlier this year the American Association of Equine Practioners (AAEP) released their guidelines for equine vaccines. A committee of AAEP members who are experts in the field of infectious diseases considered all equine vaccines and categorized the vaccines into two groups. The first group is considered core vaccines and includes the vaccines that the committee recommends all horses receive. The second group is called risked based vaccines. Not every horse needs to be given theses particular vaccines, but should be administered based on the possibility of the horse encountering that particular disease.
The group of core vaccines is considered to be essential to all horses due to the fact that the diseases that these vaccines protect against can be very serious and fatal in most cases. The diseases that these vaccines protect against are West Nile encephalitis, Eastern and Western encephalomyelitis, Tetanus and Rabies. Rabies is the one vaccine that was recently moved from the risk based category over to the core vaccine category.
There are three rabies vaccines approved for use in horses. These vaccines have excellent immunogenic properties and confer excellent protection to the horse. Adult horses require a single vaccination with yearly boosters. Pregnant mares that have been previously vaccinated against rabies need to be vaccinated 4-6 weeks prior to due date or prior to breeding. Unvaccinated pregnant mares need to be vaccinated 4-6 weeks prior to their due date. Foals need a primary series of three vaccines beginning after 6 months of age and ending at 10-12 months of age and then revaccinated yearly. If horses are exposed to rabies, there are only two alternatives. Horses currently vaccinated against rabies with one of the USDA-approved rabies vaccines should be immediately revaccinated by a licensed veterinarian and observed for 45 days for development of clinical signs of rabies. For unvaccinated horses, they should be euthanized immediately and tissues samples tested for rabies. There is no treatment for infected horses. If the owner is unwilling to euthanize the animal, then by direction from the Colorado Department of Public Health, the animal is to be placed in a mandatory 180-day strict quarantine. During the first 90 days of the quarantine the animal must be isolated at a secured facility agreeable to the health department and local agency responsible for animal control. The home property is NOT acceptable for this phase of the quarantine.
At Equine Medical Service, we are recommending that owners vaccinate their horses for Rabies as part of their fall vaccine protocol, due to recent information. Be on the watch for any signs of abnormal behavior of wild animals. Skunks are nocturnal animals and if you see them during the day call local animal control or public health authorities. Also be watchful of bats acting abnormally. Keep away from all sick or injured bats and also report these to animal control or public health officials. Remember there is no treatment for rabies in horses, only prevention.
