As you head into winter, temperatures cool and insect vectors are less in abundance in many parts, but not all, of the country. Your visit with your veterinarian in the fall includes vaccination boosters for a few risk-based diseases, namely against respiratory viruses—equine influenza virus (EIV) and equine rhinopneumonitis virus (herpesvirus or EHV-1 and EHV-4).
Immunity from these vaccines persists for about 4-6 months. Twice-annual boosters against equine influenza and EHV-1 and EHV-4 are especially important for horses that travel to clinics and competitions off the farm where they co-mingle with horses from all over. Sickness from equine influenza or EHV leads to time lost in training and competition in addition to the potential for a horse to develop pneumonia or chronic respiratory problems such as equine asthma.
It is also a good idea to boost immunity for respiratory viruses for horses that don’t leave the farm. Traveling horses might show no clinical signs upon return home, yet could carry a virus that is infective to resident horses with less robust immune systems.
In the spring, your horse was likely given his annual core immunizations that included Eastern and Western equine encephalitis (EEE and WEE), West Nile virus (WNV), tetanus and rabies. Protection from the mosquito-borne viruses generally lasts for 4-6 months, so it is a good idea to boost EEE, WEE and WNV in the late summer or fall if you live in areas in more southern states with year-round mosquitoes.
Other Risk-Based Vaccines
Potomac horse fever (PHF caused by Neorickettsia risticii) occurs in horses in some parts of the country. While vaccination against PHF does not guarantee limited risk of contracting disease, it is best given in late summer or fall due to the seasonal nature of this disease.
Strangles (Streptococcus equi) is another risk-based disease for which there is an intranasal vaccine. The vaccine is associated with a number of adverse reactions, so it should be used in consultation with your veterinarian. In high-risk areas, horses might need to be immunized twice a year against Streptococcus equi, which means you need to include a fall booster.
Good biosecurity practices are as important as immunizations to limit spread of infectious disease across your property and through your herd. A few basic precautions can reduce disease risk around the farm:
- Try to keep traveling horses away from resident horses as much as possible during a busy riding season. Stable competition horses away from the resident herd, particularly for a couple weeks following return.
- Don’t allow nose touching or shared water sources between traveling and resident horses as those are key factors in spread of disease. The same is true while your horse is off the farm at a distant venue.
- Monitor rectal temperatures of traveling horses for several days after you return home.
- Wash your hands well in between handling horses, especially the ones that have been off the farm. Change clothing if there is any suspicion that a horse is showing clinical signs of illness.
- Don’t share cleaning equipment, tack or grooming tools between travelers and stay-at-home individuals.
- Clean the trailer well after each outing.
The Bottom Line
A combination of immunization strategies and biosecurity practices both at home and away will lead to healthier horses on your property.