Pedigree Query

West Nile Vaccine
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Author:  griff [ Sat Jan 15, 2005 7:04 pm ]
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Are you sure the Menials vaccine modifies the horse's DNA? It it does do you think the stallions and mares can pass on immunity through their modified DNA?

The 2002 Ft Dodge vaccine is a killed virus while the 2003 Merials vaccine ia a live vectored recuminemt vaccine. Perhaps they modified the DNA of the live virus in the Menials vaccine so it would provide immunity without infecting the horse with WNV


Author:  Johar [ Mon Jan 17, 2005 11:35 am ]
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Both Fort Dodge's and Merial's vaccines are highly effective in protecting horses from West Nile. As others have stated, Fort Dodge's vaccine is a simple form of vaccine, being inactivated (killed). It contains their proprietary adjuvant (immunostimulant) and the killed West Nile Virus, and is administered intramuscularly. No bells or whistles. It turned out to be highly effective, which is by no means guaranteed with any vaccine, let alone a killed one such as this. In a way, that is a stroke of luck for Fort Dodge, but also for the equine community, because development and testing of a more complicated form of vaccine would have taken a few years.

Merial's vaccine represents this more complicated vaccination strategy. It is a recombinant (genetically altered) poxvirus-based vaccine. Merial are making a line of vaccines using canarypox virus as the "carrier" or backbone. They insert into the canarypox virus genome a certain gene(s) of interest from the virus you wish to protect against, in this case WNV. The WNV vaccine is basically a canarypox virus strain that has been genetically modified to contain 2 genes from WNV. Therefore the canarypox virus also makes 2 WNV proteins when administered to the horse. The reason that this virus is safe is that it is replication incompetent. It CANNOT replicate in the horse, under any circumstances. It is highly attenuated, and there is NO risk of reversion (to replication competence). However, after being administered to the horse, it can infect the horse's cells. This leads to production of many canarypox proteins within the horses cells, but also the WNV proteins of interest. The horse can then mount an immune response to the two WNV proteins it then sees. This immune response then protects the horse from infection with the virulent WNV if it encounters it naturally. Please note that the canarypox can infect (gain entry into) the horse's cells. However, it still cannot replicate, so it doesn't create "an infection". It simply produces it's proteins, and then goes no further. It cannot re-package itself into new virus particles and spread.

Recombitek is a high-tech vaccine and it is highly effective. Both vaccines (Fort Dodge's and Merial's) have been tested in challenge trials, meaning that groups of vaccinated and non-vaccinated animals were challenged with WNV to see if disease resulted. Both have been shown to protect to an extremely high degree (over 90%). As somebody else stated, the Merial vaccine is also protective after a single dose. However, it is STILL ESSENTIAL to administer 2 doses per Merial's recommendations. Protection resulting from a single dose is almost certainly short-lived. The second dose (booster) is required to "boost" the magnitude and duration of the response.

If I had to choose between using one or the other, I would choose Merial's product. While both appear to be roughly equally effective, Merial's may have longer duration of protection. Also, in general, live forms of vaccines (such as Recombitek) often have significant advantages over killed vaccines.

With all due respect to rds......Recombitek IN NO WAY alters the horse's DNA. It is only the canarypox vector's DNA that is altered. Therefore, the protection is not permanent [although any vaccine that only requires annual boosting is pretty darn good], and most definitely is not passed along vertically (from parent to foal).

Author:  rds [ Tue Jan 18, 2005 12:33 pm ]
Post subject:  West Nile

Sorry to be simple. From the Merial documentation "The inserted cDNA from the disease virus is transcribed to RNA in the (host) cells cytoplasm."

So true, the hosts (horses) DNA is not modified, and it cannot be past on. However the disease DNA is inserted in the cell, and does modify the contents of the cell. Should be as long lived as that particular cell.

Anyway, the Fort Dodge vaccine works, but takes two doses to offer any protection at all. Figure 40-45 days until the horse has protection. Whereas the Merial vaccine gives rapid response. Documentation doesn't define "rapid" precisely, but probably within 10-15 days from the first dose. Yes the second dose is needed for full protection.

Note also that the challenge testing for Merial was a full year after vaccination.

So this is very exciting technology, and most definately what I'd recommend for the best West Nile vaccine.

Now the other and equally important step to take is getting the mosquitos off the property. No mosquitos - no infections, that simple. (oops - there I go with being simple again :)

I have become a fanatic for removing water sources. Lowered my lawn sprinkling, and in fact am seeding with more drought tolerant grasses.

I am also thinking about investing in one or more "Mosquito Magnet" traps. These use a propane source to produce a moist carbon dioxide plume to attract and trap the mosquitos. They supposedly will "clean" an acre or so of area. I figure if I move them around the property to logical mosquito producing locations, I should be able to effectively reduce the mosquito population to near zip.

Elimination of the mosquitos, combined with effective vaccinations would pretty much keep the herd, and attending humans fairly safe from this disease.

Author:  kimberley mine [ Tue Jan 18, 2005 2:46 pm ]
Post subject:  Re: West Nile

rds wrote:
Elimination of the mosquitos, combined with effective vaccinations would pretty much keep the herd, and attending humans fairly safe from this disease.

Two comments.

Before you buy the Mosquito Magnet, check and make sure that it is effective against asian tiger mosquitos. Tiger mosquitos are the vector for West Nile. Anything else and you are tossing money away.

The other, very basic one: make sure you get rid of as many standing water sources as possible. That includes old tires, feed buckets, water troughs you do not clean or recirculate often, shallow drainage ditches, etc. Less standing water = fewer places for mosquito larvae to grow = fewer adult mosquitos.

Author:  griff [ Tue Jan 18, 2005 5:14 pm ]
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Will I still need two doses of the Menial WNV vaccine if I gave my mares two shots of the Ft Dodge WNV last year ?

Whay about vaccinating foals? Do they get any immunity from the shots givenmt to their dams? When should they receive their shots if ther dams received two Ft Dodge shots in 2004 and did not get their Minial shot[s] until after the foals are born?


Author:  griff [ Tue Jan 18, 2005 5:23 pm ]
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the theory behind the mosquito magnet sounds like it would work but from what I've heard it's not effective. However, i do live in Tidewater Virginia and there may be so many mosquitoes down here that the magnets are over whelmed.

Your County is stocking a small minnow that thrives on mosquito larvae and seem to only need one stocking. They are reporting good results but that will not help with old tires and those type breeding places.

Let us know what you think of your mosquito magnets late next summer


Author:  Johar [ Wed Jan 19, 2005 7:35 am ]
Post subject: 

griff wrote:

Will I still need two doses of the Menial WNV vaccine if I gave my mares two shots of the Ft Dodge WNV last year ?

Whay about vaccinating foals? Do they get any immunity from the shots givenmt to their dams? When should they receive their shots if ther dams received two Ft Dodge shots in 2004 and did not get their Minial shot[s] until after the foals are born?



These are excellent questions. First of all, one dose of the Merial vaccine should do. You can feel confident that the 2 dose regimen of Fort Dodge's product will protect as long as their recommendations suggest (until they require a further booster). If you choose to switch to Merial's vaccine at that stage, you can administer one dose, and then give annual boosters for as long as you deem necessary. Apparently Merial have even conducted this experiment:

As for when to vaccinate foals, unfortunately, I am not sure off-hand. I would hope that that information is on the product sheet, or at least available from the company. In short, yes, the foals do get immunity transferred from vaccinated dams. In general, anything that induces antibodies in the mare will result in the accumulation of those antibodies in colostrum (as you know). These antibodies when ingested by the foal can then mediate "interference" with the same vaccine when it is subsequently administered to the foal. The duration of "maternal antibody interference" depends on 2 things. (1) how high the titer of such antibodies was in the mare, and hence, in her colostrum; and (2) how well the foal nursed and ingested colostrum. Maternal antibodies persist in the foal with a "half-life". Meaning, they decline by 50% after each half-life period. So the more antibodies the foal ingests from colostrum, the longer those antibodies offer some sort of protection (and some interference against vaccination). It's a trade-off. In the case of EHV-specific antibodies, that half-life is 28-30 days. So if the foal starts at an arbitrary titer of 1000, then at 1 month of age that titer is 500, then 250, 125 etc. When the titer falls below a critical threshold, that is when those remaining antibodies are too few to mediate maternal interference. For EHV, you can usually vaccine successfully starting at 4-6 months of age. For influenza, the maternal antibodies persist for longer, so it's good to wait until about 9 months of age to begin vaccinating. Unfortunately I don't know what the half-life of WNV antibodies are, or if that has been measured. But again, Merial should have recommendations that are better than my guess.

Author:  griff [ Wed Jan 19, 2005 8:15 am ]
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Thanks Johar


Author:  BJ [ Tue Feb 15, 2005 1:25 pm ]
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griff wrote:
according to there are two WNV vaccines licensed for use in the USA> Fort Dodge's 2002 vaccine isa killed virus while Menial's 2003 vaccine is a live vectored recuminent vaccine.

Any thoughts on which to use?

Also, what do you think of my vet's recommendation to vaccinate after foaling and before breeding?


Anyone else have a vet recommend this? I was just fretting over this because of an old West Nile vaccination thread (old board I think) and I couldn't remember if it was o.k. to vaccinate BEFORE breeding, but not while in foal... Just acquired two mares, one without med records and wanted to hold off on breeding her if getting the vaccine would create a problem. Unfortunately, it seems, Vets and/or Farm Mgrs. SOMETIMES just pass out the "expedient for them" opinion, so I'm glad this is being discussed again.

Author:  Roguelet [ Wed Feb 16, 2005 5:35 am ]
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My Vet recommends doing this vaccine along with the others, 30 days prior to foaling. We've done that with all of our broodmares every year since the vaccine first became available and have never had a problem at all.

When the "lost foals" group started making noise, I asked our vet if he had any problems with side effects on any other horses and he said no. He deals with a LOT of horses, so that was good enough for me. I also know of several other TB farms that use the vaccine yearly as part of their pre-foaling series, all without incident. So, I will continue to use the vaccine on the same schedule as all of the others and hopefully will never regret that decision. :wink:

Author:  valerie [ Wed Feb 16, 2005 7:21 pm ]
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My vet doesn't like me to vaccinate my foals until they are at least 5 months of age. We have done this for a number of years with no ill effects on the horses. I do this with the 5way and the WNV and by the way I have changed all mine to Merials vaccine and like it much better. Not at much site reaction like with the Ft. Dodge products.

Author:  sulphurfire [ Wed Feb 16, 2005 11:18 pm ]
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I just read this on the west nile and thought some of you might be interested in what they said regarding the vaccine and breeding mares.

Author:  Kirsten [ Wed Feb 16, 2005 11:19 pm ]
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I am leary of vaccinating my mares with WNV.
Last year my mare aborted 10 days early as did my friends mare bred the same time. Both mares were vaccinated first trimester with the vaccine ( unsure of which one)
We had also heard of 4 other ppl with the same dilemma. I know ill probably get shot down here for it but im way too terrifed to go thru that again.
I will vaccinate this years pregnant mare after she foals as will my friend. Both our mares are due 2 weeks apart again. Just hope it doesnt happen on April fools day again.

Author:  BJ [ Thu Feb 17, 2005 8:25 am ]
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sulphurfire wrote:

I just read this on the west nile and thought some of you might be interested in what they said regarding the vaccine and breeding mares.

Thank you S! It mentioned the correlation between mares in "fescue pastures", so I looked that up and found this article below. A picture of the grass (many of you probably already know this...I did not) is at this link: There are probably other articles re: toxic plants and things for animals at this site.



Festuca arundinacea

(grass family)

TOXICITY RATING: Moderate to high, depending upon individual circumstance.

ANIMALS AFFECTED: Horses, cattle, possibly other ruminants.

DANGEROUS PARTS OF THE PLANT: Seed head, stem and leaf sheath

CLASS OF SIGNS: Reproductive problems, "poor doers", lameness, dry gangrene, fever, death.

PLANT DESCRIPTION: This grass (fig. 15), often cultivated in wet pastures for forage or for turf, is a perennial, 3 to 4 foot tall clump grass with medium-wide leaves that are rough-ribbed on top. It has no rootstocks (rhizomes). The heads are open and many-branched. Escaped plants may be found along roadsides and in waste areas, especially in the southern half of the state.

SIGNS: Toxicity is the result of an endophytic ("inside the plant") fungus, Acremonium coenophialum, which is believed to enable the grass to be more hardy and outcompete other grass species. The grass itself is not toxic. The fungus is passed in the seed, and is not transmitted directly from plant to plant.

In horses, pregnant mares are most at risk when eating fescue, since the alkaloids produced by the fungus inhibit prolactin release. Mares will have an increased risk of prolonged gestation, abortion, stillbirth, dystocia (difficult birth), foal mortality, retained or thickened placenta, no milk, and mare death (in foaling, or from a retained placenta).

In cattle, several syndromes have been reported, including fescue toxicosis (summer slump), fescue foot and abdominal fat necrosis. Summer slump causes slower gains, decreased milk production, poor appetite, retention of winter coat, reproductive problems, and elevated temperature. Diarrhea may also be present. Summer slump tends to occur in the warmer months, but has been noted at any time of year, and is the most common of the three syndromes. Fescue foot tends to develop in the late fall and winter, and the extremities (typically tail, ears, and rear feet) undergo necrosis ("death"). Another name for this type of necrosis is "dry gangrene". Fat necrosis develops when areas of fat inside the abdomen die.

Additional note: Fescue can accumulate nitrates under conditions of overfertilization (see the section on oats for more information on nitrate toxicosis).

FIRST AID: There is only supportive and symptomatic treatment once signs appear. A veterinarian can advise on treatment of more severely affected animals. Pregnant mares will be likely to need assistance when foaling and in the post-foaling period. Foals that survive will require supplemental colostrum. Management and prevention are the best means to minimize losses.

SAFETY IN PREPARED FEEDS: The toxin remains active in hay.

PREVENTION: There are several options, depending on the farm situation. Fungicides do not work, so animal and pasture management are the only viable alternatives. Pastures can be tested for the presence and degree of fungal contamination, and reseeding may be required. If reseeding the pasture is not feasible, keeping the pasture short will prevent seed formation. Feeding other forages, such as other warm season grasses or legumes, will be of benefit. Fescue pastures can also be diluted with legume planting (red or white clover). Heavy fertilization may make the problem worse, especially in cattle. If fescue has to be used for mares, at least avoid feeding fescue hay or pasture during the last 30 to 60 days of gestation to minimize problems. Endophyte-free strains of fescue exist, although they do not grow as well as tall fescue with endophyte.

Author:  BJ [ Thu Feb 17, 2005 8:28 am ]
Post subject: 

The Cornell U article also gave this government link for more info:

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