Fall is a good time to add equine vaccination and deworming to your to-do list. Our Equine Field Service’s equine vaccination guidelines can help horse owners determine which vaccination schedule is right for their horse.

Core horse vaccines

Ideally, all horses in a herd should be on the same vaccination and deworming schedule. This helps simplify record keeping, minimizing replication and transmission of infectious agents in a herd and indirectly protecting those horses in the herd that responded poorly to vaccination, thereby optimizing herd immunity. All equines should receive core horse vaccines at least annually. Their efficacy and safety are easily demonstrated, they provide high patient benefit, and low patient risk.

Core horse vaccines include:

  • West Nile virus
  • Eastern equine encephalitis
  • Western equine encephalitis
  • Rabies
  • Tetanus (horses should also receive a booster after incurring a significant wound)

“Risk-based” vaccines

The decision to vaccinate with non-core or “risk-based” vaccines is based on the exposure or risk of disease of each individual horse. Risk factors include anticipated exposure, environmental factors, geographic factors, age, breed, use, and sex of the horse. Consult the American Association of Equine Practitioners’ risk-based vaccination guidelines to make an informed decision about your own horse.

“Risk-based” horse vaccines include:

  • Strangles
  • Equine influenza
  • Equine herpesvirus (rhinopneumonitis)
  • Botulism
  • Potomac horse fever
  • Rotaviral diarrhea
  • Anthrax
  • Equine viral arteritis
  • Leptospirosis
  • Venezuelan equine encephalitis (VEE)
  • Snake bite

Side effects are a possibility after a horse receives any vaccination. To minimize the risk of side effects, horses should be in good systemic health when vaccinated. If your horse is known to have allergic reactions, or has had a vaccine reaction in the past, an anti-inflammatory drug such as Banamine or dexamethasone may be administered prior to vaccination. The morning of vaccination day is a good time for this administration.

Monitor your horse for these side effects for a few days after being vaccinated:

  • Sore muscles
  • Heat/swelling/abscess at the injection site
  • Fever
  • Colic signs (most commonly associated with Rabies vaccine, but rare)
  • Hypersensitivity (allergic reaction)

Horse deworming schedules

In addition to ensuring your horse is vaccinated against disease, it is also important to protect your equine against parasites by adopting a horse deworming schedule tailored to your herd.

There are many ways to provide parasite protection, but “targeted dosing” is the most effective way to keep worm burdens low in your herd. Targeted dosing involves having your veterinarian perform monthly fecal egg counts on all grazing horses and administering an anthelmintic (dewormer) to those that have a count of >200 eggs per gram. This method minimizes the overall use of anthelmintics, which reduces anthelmintic resistance. Anthelmintic resistance decreases the effectiveness of each medication against parasites, so we do our best to avoid adding to this problem!

“Strategic dosing,” or deworming the entire grazing herd only in the spring/summer, is another way to keep anthelmintic resistance low. This approach is most effective in areas where a dry heat is maintained for several weeks, which is detrimental to parasite survival. “Interval dosing,” or deworming year-round at synchronized times (every two months), should be avoided if possible, as it gives parasites the highest chance of developing anthelmintic resistance.

Our focus for deworming horses is on parasites called small strongyles (cyathostomins), because all grazing horses are affected to some degree by these parasites. The true goal of parasite control in horses (and other equids) is to limit parasite infections so animals remain healthy and clinical illness does not develop. The goal is not to eradicate all parasites from a particular individual horse. Using our preferred “targeted dosing” method, it is usually necessary to treat for cyathostomins at least twice a year, in the late spring and fall. Ivermectin and moxidectin remain the foundation for control of these most common parasites. Additionally, praziquantel should be used in the fall (or more often if found on fecal exam) to treat tapeworms.

In addition to maintaining a solid horse deworming schedule, we recommend practicing “non-chemical pasture hygiene” by removing feces from grazing areas once or twice weekly.