Horses should get an initial vaccination with a booster following 3-6 weeks after the first vaccination. Horses will not be protected until 3 weeks after the booster shot. Horses that had their initial series should get boostered at a minimum once a year (if done close to mosquito season) or may have to be done more frequently if they are exposed to mosquitoes for more than 5 months; for example horses traveling to Southern states, brood mares that were vaccinated early in the season for purposes of getting it into the colostrum etc..

Updated: January 2003

Rabies in Wisconsin

In December 2002 a recumbent horse was euthanized and later confirmed as Rabies positive. While Rabies in horses is rare it is a frightening disease since it always results in death and also can be transmitted directly from horses to humans. While horses are more likely to be depressed rather than aggressive people often do put their hands in or near a horse's  mouth to see why the horse is not eating.
Rabies in Wisconsin is transmitted by skunks or bats. If you have skunks around your barn or pastures vaccinating your horse against rabies is a good idea. It can be given at any time of the year and is then given every 12 months. Foals can be vaccinated as early as 4 months of age.

Potomac Horse Fever - new developments 

When PHF first caused illness in horses we only new that it was somehow connected to warm water. Three to four years ago it was discovered that microscobicly small crustaceans were the culprit. They entered small fresh water snails which when swallowed by horses caused high fevers, diarrhea and often led to severe laminitis.
This still did not answer how horses not living near ponds or streams acquired PHF. It has now been found, that the crustaceans also entered the larvae of the cadysfly. Once hatched, the fly could go anywhere and be picked up by a grazing horse.
Vaccinating your horse may not protect your horse but will make an infection less severe.

Potomac Horse Fever