Vaccinations
Deworming
Other Recommendations
The selection of the best vaccination strategy for each group of horses always involves a risk-benefit analysis. Unfortunately, there is no perfect vaccine (100% safe, 100% protective), and some of the most widely-used products are minimally protective and carry some actual health risks of their own. In addition to rare side-effects of vaccination, such as local swelling or allergic reactions, there is some evidence that too-frequent vaccination is itself a possible risk factor. Although recent and ongoing research has suggested some risk of over-vaccination in people, and possibly, in small animals (dogs and cats), no scientific work has yet been published regarding a similar risks for horses. We will continue to monitor the literature for such information, but also welcome your input on this topic.
Fortunately, equine vaccine technology is vastly superior today, compared with even just 7-10 years ago. Not only are the newest vaccines MUCH more thoroughly tested these days (by measuring degree of protection, as well as safety), new technologies are emerging to confer longer-lasting, more balanced protection.
Thus, when choosing the best vaccination strategy for your horses, you have to balance the actual risk of infection (likelihood of exposure AND severity of the disease) with the potential benefit of vaccination (degree of protection conferred, risk of adverse effects). We are very happy to consult with you regarding formulation of the best vaccination strategy for your horses.
For comparison, consider two widely-used vaccines, one against West Nile Virus (WNV) and the other against Strep equi ("Strangles") infection. The vaccine against WNV is highly effective, as horses which receive the initial two-shot primary series and regular boosters. Add to this the fact that 30% of horses infected with WNV will die. So the risk of fatal illness is high, and the vaccine is highly effective, with only very rare, typically mild side-effects. Administration of the WNV vaccine(s) is relatively easy to routinely recommend.
In contrast, while the intra-nasal vaccine against Strangles is the best that researchers have yet developed, the vaccine offers only partial protection against infection. Most exposed horses will still develop mild to moderate clinical signs of infection. Yet the manufacturer of this vaccine reports that more than one in 30 horses will develop some side effects following vaccination, and over one in 300 develop more serious side-effects requiring more medical intervention. And while the disease is a mess, it is rarely a fatal condition when diagnosed and treated aggressively. So the risk of fatal illness is very low, and the vaccine is moderately effective, with relatively common, occasionally serious side effects. Administration of the Strangles vaccine is harder to routinely recommend.
The routine useage of most vaccines falls somewhere between these two extremes. Again, the potential benefit of each vaccine must be evaluated, along with the relative risks of actually contracting the disease. You must also consider the financial cost of vaccinating versus infection, and the risk of potential side effects. Our veterinarians are always happy to help you weigh the potential pros and cons of vaccination in order to help you develop the strategy that makes the best sense for you.
Overwhelmed yet? With our knowledge of emerging technologies and tried-and-true vaccines, as well as local and national disease epidemiology, we feel that the veterinarians at Montana Equine are exceptionally well-qualified to help you design a vaccine strategy that works for you.
For more information on vaccinations, please review Dr. W. David Wilson's Vaccination Guidelines for Horses in the Western United States.
Montana Equine's Basic Vaccination Recommendations:
| Spring (April) | Fall (October) | |
| Horses < five years | Tetanus /Eastern+Western/West Nile Encephalitis
(+/- West Nile Booster 4 wks after 1st WNV vacc) Influenza/Rhinopneumonitis |
Tetanus/Eastern + Western Encephalitis Influenza/Rhinopneumonitis |
| Horses > five years | Tetanus/Eastern+Western/West Nile Encephalitis
(+/- West Nile Booster 4 wks after 1st WNV vacc) Influenza | Tetanus/Eastern + Western Encephalitis Influenza |
Strangles:
- We recommend Intra-Nasal Strangles vaccination (twice yearly) only when there is a current or recent outbreak on the premises. We may recommend giving this vaccine under certain other circumstances.
Pregnant Mares:
- Vaccination with "killed Rhino" (we most often recommend "Pneumabort K") is a critical means to minimize the risk of abortion due to Rhinopneumonitis (Herpes) Virus. This should be given at the beginning of the 5th, 7th, and 9th months of gestation.
Foal Shots:
- Foals born to mares fully vaccinated at 10 months of gestation:
- Begin vaccinating at 5 months of age
- Plan for booster shot at 1 month post-vaccination
- Foals born to mares who have not been vaccinated (other than Pneumabort):
- Begin vaccinating at 4-6 weeks of age
- Plan for booster shot at 1 month post-vaccination
- Under certain circumstances, we will recommend Rabies vaccination. This is a one-yearly vaccine.
Generally, we recommend de-worming four times per year. Most deworming medications sold over-the-counter work fine, but it is important to keep in mind the basics of the worms' life cycle. You may notice that Moxidectin (the product "Quest") is not included among our routinely-recommended de-wormers. Although there are occasionally circumstances when we might recommend Quest, side effects have been reported, especially in younger horses.
Overall, we are fortunate that our hot dry summers and cold winters help to minimize total worm burdens in our environment. But it is not correct to assume that your horses do not require regular de-worming. It is not uncommon for us to hear from clients who wish to minimize the amount of de-worming medication they use and we generally support the philosophy that "less-is-more," especially when it comes to any type of medication. However, the readily available over-the-counter de-worming medications are generally very safe and, in fact, ivermectin is increasingly used to treat parasitic infections in people.
These de-worming medications have been vital in decreasing the severe clinical signs of worm infestation seen prior to their introduction into regular equine medical practice. Their routine use does not just reduce simple unthriftiness, but also is widely understood to massively reduce the risk of simple and severe colic in all age groups of horses. However, as mentioned above, we are open to helping you develop effective alternative strategies for minimizing worm infestation in your horses. Please contact our herd health and Internal Medicine specialist, Dr. Peter Heidmann (406-285-0123), to discuss your goals and to personalize the safest approach for your animal(s).
Many clients ask for more information about worms' resistance to the commonly used de-worming medications. Again, our regional climate may provide a significant benefit -- most scientific reports documenting anthelmintics resistance have been based in much more temperate climates, most notably in the Southeastern United States (Georgia and Alabama) and Europe (Belgium). These studies are very difficult to conduct, but there is little evidence that resistance is widespread. In addition, scientists and veterinary researchers remain divided about the potential benefits of rotating medications versus sticking with one de-wormer long-term. There is actually conflicting evidence suggesting that each strategy may be superior. At this time, we generally recommend a rotational strategy, but will support you in any well-formulated strategy.
The outline below reflects our general overall de-worming recommendations. Are your horses on drylot? Do they travel a lot? Are there many or few horses per acre? All these questions can contribute to helping design a de-worming program to suit your circumstances. As always, we recommend routine testing of your horses' feces to monitor their current potential worm burden. Although some worms (encysted small strongyles and tapeworms, most notably) usually escape detection, routine testing can help identify horses with heavier parasite burdens, allowing treatment and minimizing the risk not just for themselves, but for all the other horses in the local environment.
| Yearlings | Adults, Large Pasture (Low Population Density) | Adults, Drylot / Paddock (High Population Density) | |
| Spring (April) | Febendazole (every six weeks) | Ivermectin (with praziquantel) | Ivermectin (with praziquantel -- Once each in March and June) |
| Summer (July) | Febendazole (every six weeks) | Febendazole / Oxibendazole | Febendazole / Oxibendazole (Or Panacur Powerpack) |
| Fall (October) | Ivermectin | Ivermectin | Ivermectin (Once each in September and November) |
| Winter (January) | Pyrantel Pamoate | Pyrantel Pamoate | Pyrantel Pamoate |
We will be adding content regarding additional preventative care recommendations in the near future.
