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.
As a result of recent research, our deworming protocol has changed at Montana Equine. In the past, we have recommended deworming four times per year with specific dewormers targeting specific parasites. This is no longer our recommendation. The latest research has shown that in a herd setting, 3% of horses will carry 90% of the worm burden. In addition, there is a growing concern regarding parasite resistance to dewormers that are currently on the market. Although this resistance remains rare in Montana and other similar climates, we are now recommending that all horses greater than one year of age be screened for parasites via a fecal float, instead of arbitrarily dewormed. This will help identify chronic carriers, ensure that we decrease parasite resistance, and thus maintain drugs that are efficacious against parasites in the future.
A fecal float is a cheap, non-invasive test that requires only a manure sample from your horse. This manure sample is mixed with water and spun in a centrifuge and then strained. The manure pellet left in the bottom of the tube is then mixed with a sugar solution, covered with a cover slip, and placed in the centrifuge for one last spin. The parasite eggs float to the top and stick to the cover slip. The cover slip can then be placed on a slide and evaluated using a microscope. If parasite eggs are found in your horse’s manure, the eggs are identified and recommendations for the specific dewormer that your horse needs can be made. One thing to keep in mind is that tapeworm eggs and encysted strongyle eggs are too heavy to float to the top while being centrifuged. As a result, we do recommend that you deworm your horse(s) at least once a year in the fall with an ivermectin/praziquantel product (such as Zimectrin Gold, or EquiMax).
We realize that there are herd situations where obtaining an individual sample from every horse might be challenging and that individual screening requires a larger amount of money up front. However, fecal floats will identify chronic carriers and reduce the de-worming treatment for the rest of the herd thus minimizing the money spent on dewormer in the future. In addition, the horses that are not burdened by parasites will not receive medications that they don’t need. We are open to helping you develop effective alternative strategies for minimizing worm infestations in your horse(s). 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).
When considering deworming your foal, we would recommend beginning to deworm at 6-8 weeks of age without any need for a fecal float first. Foals can be affected by large numbers of ascarids in their gastrointestinal tract that in turn, can cause impactions. You should deworm your colt 6-8 week old colt four times, 6-8 weeks apart with a product such as fenbendazole or oxybendazole. Following this initial series of deworming, your foal will be old enough to begin on a yearling/adult program of annual fecal floats and ivermectin/praziquantel.
We do not recommend using the drug Moxidectin (the product “Quest”) on a regular basis. Although there are occasionally circumstances when we might recommend Quest, side effects have been reported, especially in younger horses.
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.
