Equine Vaccinations

[EqSci]

Regarding the 'big movement' to decrease vaccinations in small animals...

Why is this not happening in the equine world? (or is it?) As far as I know, people are vaccinating horses more than ever. I hope I'm not showing my ignorance here, especially since I own a horse.

I have never heard of the 3-year rabies vax for horses, whereas it's the norm in most SA clinics now. Thoughts, explanations?

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[Groominator]

I admit i don't know much about horses, so i can't add anything useful on that.

But I wish the word on vaccinating less often got out a bit more and faster. My vet still pushes annual vaccs and gives me a look when i refuse. Really wishing i could make Dr. Jean Dodd's talk on Vaccines at Rutgers this month but i don't have the extra money to go to that seminar right now

 

[WhtsThFrequency]

Me too, I toyed with the idea of heading to Rutgers but I can't afford it There are still "core" vaccines and "optional" vaccines.... so that helps some. The old gelding out in the field that never goes anywhere doesn't need EHV vaccination....but I haven't heard of any "minimal vaccination" movements like there have been in SA, either. Anyone know? I'd wager it's a matter of not enough research being done in the area. I'm admittedly not very knowledgeable on the equine world, beyond a few specific breed interests.

 

[eventualeventer]

My guess is that one of the contributing factors is $ for equine research. A couple clients at my old job opted to run titers on their horses instead of vaccinating, but the titers ended up running around $300 with minimal markup from the vet clinic. Also, the vet mentioned that there aren't a lot of data showing what a sufficiently protective titer is for all of the horse diseases; also, for some diseases, antibody titers are not necessarily indicative of actual immunity in the face of the disease, which also means that re$earch is required to support more spaced-out dosing schedules. It is a lot more expensive to keep horses around to do research on them than small animals.

There is no 3-year rabies vaccine licensed for horses -- again, I don't think the re$earch required to license such a vaccine has been done -- so no vet is going to risk their license, not to mention state laws requiring yearly rabies shots, by recommending a 3-year vaccination schedule.

Some other possible factors that I've come up with:

- Several equine diseases are either relatively recent (WNV), are re-emerging (PHF cases seem to be on the increase in the mid-Atlantic compared to the 1990's), or are in people's minds because of increased reporting and communication (the neuro form of EHV-1), so I think some of the vaccination practices are based on some combination of fear, misconceptions, and lack of data.

- There may be some tenuous, anecdotal links between vaccines and episodes of laminitis or worsening of symptoms in horses with metabolic disease (Cushing's/IR), but I have not heard of fibrosarcomas or hemolytic anemias being associated with vaccination in horses, unlike in cats and dogs.

- Most dogs and cats stick close to home. Some dogs may go to dog parks and interact with strange dogs there, and a handful (relative to the entire population) go to dog shows, but your average house pet does not get exposed to nearly the same number of strange animals and pathogens as a horse who is boarded at a large boarding stable with high turnover and no quarantine protocols (most big barns around here just chuck the new horses into the main barn and turnouts without any sort of isolation period) and goes to shows (or is exposed to horses who go to shows) on a regular basis during the warm months.

- I don't know much about small animal vaccines, but some equine vaccines, especially PHF, are not very good at stimulating a lasting immunity and really do need to be given frequently. I live/work the mid-Atlantic, a hotbed of PHF, and the practice I used to work for, which still treats my "adopted" horses, sees multiple cases and loses one or more horses a year to PHF. They recommend vaccinating twice a year, in early spring and late spring/early summer, to try to maximize protection during mid to late summer, when the disease is at its peak, and they think that (anecdotally, of course, not a real study) this has made a big difference in mortality. Vaccinated horses still get PHF and still die sometimes, but PHF used to sweep through barns and leave horses literally walking out of their feet left and right.

 

[EqSci]

If I had to guess I would say that horses are at an increased risk for rabies given that they (commonly) live outside, and barns themselves are hot spots for wildlife. The other vaccines are protection against very real, ongoing threats of disease that are usually seasonal so it's common to give boosters in the spring.

Of course, arguments to those statements could certainly be made quite easily.

 

[EqSci]

Thanks eventualeventer... you made some great points. I've actually added Potomac to the list of vaccines I'll be giving my horse this year after seeing several horses affected with it last year... before that, my impression was that it was nearly eradicated in certain areas. EEE seems to be on the rise again as well (at least in my state).

Do you know the results of the titers that those clients requested and how long it had been since they vaccinated?

 

[Gordo]

I really dont have an answer for your question, but for one I am fine with my horse getting a rabies vaccine every year instead of 3 like my dogs. My horses are exposed to all types of animals living were they are at, so I am fine with that. I vaccinate for rabies, West nile, EEW/EEE, and rhino flu. I live in Florida so the west nile and EEE/W is a must.

 

[eventualeventer]

Unfortunately, I don't remember the results of those tests, and I no longer work at that practice, although I am friends with one of the vets. I'll ask him next time I see him.

PHF is not an eradicable disease like polio or smallpox because it is maintained in the wild with a number of intermediate hosts. It's more like rabies and WNV in that horses tend to be dead-end hosts* that are not necessary to the disease's survival. Its incidence went down after the development of the vaccine in the late 1980's, but there have not been any new vaccines incorporating different strains since then. It's not clear whether there are other factors that have affected its prevalence in the wild. It has not been proven exactly how the life cycle is completed and maintained in the wild -- birds and bats are thought to be involved -- let alone whether it affects its intermediate hosts enough to generate significant selective pressures for an immune response and a cycle of outbreaks and resistance like seen with WNV.

PHF is a nasty disease (I think of severe laminitis as one of the cruellest diseases known to horses), and I've noticed that a lot of horse people I talk to on the Internet are not aware that it is not restricted to the mid-Atlantic. The Great Lakes and the Shasta River Valley in CA are other hotspots, but it has been found all over the U.S. and Canada, although it seems to be localized to specific watersheds. E.g., in MD, PHF is common along the upper Potomac River and its tributaries, but it is much rarer in southern MD along the Patuxent and the tidal Potomac.

*Technically, horses could spread rabies, but they don't tend to go around biting raccoons and skunks and contributing to its maintenance in the population.

 

[eventualeventer]

Shoot, I wrote that the PHF vaccine was developed in the 1980's when I should have written 1990's. The disease was described in the 1980's.