Post by Calaminty Jane on Jan 31, 2009 12:40:23 GMT -5
Worms and the Equine
This information is supplied by Richard Mumm, of Enterprise , Oregon . He did quite a bit of research for this article which first appeared as a post on the Wildhorses mailing list. He is not a veterinarian, but this is excellent information you can use in association with your vet's advice.
Quest is borderline dangerous to give a horse, in my opinion. I've spent
a fair amount of time on the internet searching out info on horse
de-worming medicines, and Quest (Quest is the brand/trade name, the
chemical name is moxidectin) is the least safe of any of the commercial
worm medicines currently in popular use. There are reports of it killing
horses who were in marginal condition, undernourished and/or a little
weak, also foals.
Quest (moxidectin) is expected to cause physiological problems in a
healthy horse at 5 times the effective dose. That is, if you give a
healthy horse 5 times the dose recommended by the manufacturer, according
to the horse's weight, you could expect to see problems (neurological
problems would be most likely, with Quest/moxidectin), or have the horse
die.
By contrast, ivermectin (brand names Zimecterin, Eqvalan, Rotectin 1,
Equimectrin, etc.) is not expected to cause problems until 60 times the
effective dose is given.
Oxibendazole (brand/trade name: Anthelcide EQ) is not expected to cause
problems until 60 times the effective dose is given.
Fenbendazole (brand names Panacur, Safe-Guard) may cause problems at over
100-200 times the effective dose, although apparently when testing for
side-effects from fenbendazole, the researchers had difficulty producing
any problems at all, at any amount of overdose.
Pyrantel pamoate (brand names Strongid P, Strongid T, Rotectin 2) is safe
for a healthy horse at up to 20 times the effective dose.
Quest's claims to fame are that it will kill bot fly larvae, encysted
small strongyle larvae, and that it only needs to be given every 84 days.
Fenbendazole, given at double dose according to the horse's weight for
five days in a row, will also kill encysted small strongyle larvae, and
is *much* safer for the horse. As for bots, ivermectin does a great job,
and is also *much* safer than Quest/moxidectin. (also, Quest/moxidectin
only eliminates about 15-25% of encysted small strongyles, where
fenbendazole eliminates *all* encysted small strongyle larvae - see
"*Update 8/7/00" at bottom of page, below, and the notes from a lecture
by Dr. David Laird, also below, for more information)
I have had readers make the comment that it would be difficult to
mistakenly give a horse 5 times the recommended dose of Quest/moxidectin.
That is not the point. The point is that a worm medicine that is likely
to cause obvious metabolic/physiological problems at 5 times overdose is
likely much more toxic to the horse than a worm medicine that may cause
obvious metabolic/physiological problems at 20, 60 or 100-200 times
overdose, and is much more likely to cause subtle metabolic/physiological
problems that may not be immediately apparent to a human observer at the
recommended dose than another worm medicine that may cause obvious
metabolic/physiological problems at 20, 60 or 100-200 times overdose. It
is a matter of relative toxicity.
Also, when worming foals it would be fairly easy to give several times
overdose of Quest/moxidectin, and there isn't much room for error.
In spite of the large amount of worm medicine given to the horse during
the double-dose-for-five-days-in-a-row treatment with fenbendazole,
experience and research has determined this procedure to be entirely safe
for the horse, and is the only known way to eliminate *all* encysted
small strongyle larvae.
Larval cyathostomiasis (or small strongyle infection) is a distinct
clinical syndrome that occurs with the mass emergence of encysted larvae
from the intestinal wall. This release happens more in winter and spring.
Small strongyles are less damaging than large strongyles since the larval
migration is limited to the intestinal lining. However, the damage
impairs normal gut motility, leading to signs of colic, colic being the
most common cause of death in horses.
I believe a good, safe worming program will incorporate fenbendazole or
oxibendazole, ivermectin and pyrantel pamoate on a rotation basis.
Fenbendazole (or oxibendazole) in fall and again in spring, followed each
time, at appropriate intervals, by pyrantel pamoate paste, and then
ivermectin (or followed first by ivermectin, then pyrantel pamoate), is a
good rotation program.
The frequency of giving your horses worming medicine depends on how
frequent their contact with other horses they're not pastured with is,
and how good their pasture management is. Horses with poor pasture
management, and/or frequent contact with horses they're not pastured with
should be given worm medicine on a rotational basis every 6-8 weeks.
Horses with good pasture management and little or no contact with horses
they're not pastured with may get by with being given worm medicine every
3 or 4 months on a rotational basis. [Note: This assumes you worm all
horses pastured together at the same time.]
Also, some people swear by the daily wormer pyrantel tartrate (brand
names Strongid C, Strongid C 2x, Equi-Aid CW and Equi-Aid CW 2x). Some of
the endurance riders say that this wormer can make colic more likely.
However, most endurance riders ride Arabian horses, which are said to be
a little more prone to colic anyway, and most of us are not riding our
horses 50-100 miles in one day, as the endurance riders do.
The daily wormer would need to be supplemented with, at least, ivermectin
(in fall, after a good freeze), as pyrantel tartrate daily wormer doesn't
kill bots. A twice yearly course of fenbendazole, double dose according
to the horse's weight for 5 days in a row, is needed to eliminate
encysted small strongyle larvae. A twice yearly treatment with pyrantel
pamoate, double dose according to horse's weight for two days in a row,
*or* 10 times the normal daily dose of pyrantel tartrate daily worm
medicine for two days in a row, will be necessary to eliminate tapeworms.
Equi-Aid CW and Strongid C are identical products marketed by two
different manufacturers - the only difference is that Strongid C costs a
little bit more, and the company that manufactures and markets Strongid C
(Pfizer) offers a guarantee that if your horse colics while on Strongid C
(for *any* reason) they will contribute $5000 toward any resulting
medical bills. You have to live up to certain requirements in order to
qualify for the guarantee, such as certain immunizations have to be done
on a regular schedule, and you have to use a "purge" dewormer, such as
fenbendazole, oxibendazole, ivermectin or pyrantel pamoate at least twice
a year. Your vet should have details on how to sign up for the program.
Please note that if you give a horse that has a lot of worms an effective
purge type worm medicine (any commercially available worm medicine other
than the daily wormer), so many worms can die at once that it can clog up
the horses veins, heart, lungs and other parts of the body (what part of
the body depending on the type of worm) with dead worms and cause the
horse a lot of suffering, maybe even kill it.
So, horses that are undernourished or weak for some reason, or that are
suspected to have a lot of worms, should be fed pyrantel tartrate (daily
wormer) for 2-4 weeks, then the horse should be wormed with ivermectin,
dosage according to horse's weight, then *6-8 weeks later*, wormed with
fenbendazole (double dose according to the horse's weight for 5 days in a
row), and then continue with a regular worm medicine rotation program,
such as described above.
The pyrantel tartrate daily wormer, according to one of the vets at the
clinic where I have my horses taken care of, does not have to be
discontinued to administer oxibendazole, fenbendazole, ivermectin or
pyrantel pamoate. He did say that it is probably a good idea to not
administer Quest/moxidectin while feeding horses the pyrantel tartrate
daily wormer medicine. I think it's a good idea to not administer
Quest/moxidectin at all, ever.
Here's the bottom line:
ivermectin - kills everything except encysted small strongyle larvae &
tapeworms.
pyrantel (pamoate, tartrate) - kills everything except bots & encysted
small strongyle larvae (double dose of pyrantel pamoate paste for two
days in a row, dosage according to horse's weight, is required to
eliminate tapeworms. alternatively, giving 10 times the normal dose of
pyrantel tartrate daily worm medicine for two days in a row will also
effectively eliminate tapeworms - see "*Update 8/7/00" at bottom of page,
below).
oxibendazole - wide spectrum, safe and effective dewormer. could not
determine if oxibendazole has any effect on encysted small strongyle
larvae or tapeworms. does not kill bots.
fenbendazole - kills everything except bots (double dose according to
horse's weight for 5 days in a row required to eliminate encysted small
strongyle larvae & tapeworms). The least expensive way to use
fenbendazole probably is to purchase Panacur granules, which are
available through:
KV Vet Supply
phone # 1-800-423-8211
website address: www.kvvet.com
KV Vet Supply's most recent price was $1.89 per packet (or $1.69 per
packet if you buy 10 or more packets at a time). One packet will worm 500
lbs of horse, one time - single dose. you can mix it right in with your
horses' feed. you might want to add a couple of tablespoons full of
molasses to cover the taste.
PROBIOTICS IN CONJUNCTION WITH WORMERS
It's a really good idea to give the horse probiotics, especially a day or
two after you give them worm medicine. The worm medicines we give our
horses may kill or upset the horse's natural, beneficial intestinal
bacteria, and it needs to be replenished somehow.
The probiotics are beneficial intestinal bacteria which are natural to
the horses instestines. These can get killed off by worm medicines,
stressful conditions, etc., and when given to the horse by mouth or added
to the horses feed will multiply in the horses gut, helping them digest
their food, and their adequate presence in the gut makes no room for
infective bacteria.
Among ingredients to look for in whatever probiotic product you select
may be the following (the more different kinds, the better):
lactobacillus acidophilus
streptococcus faecium
aspergillus oryzae
bacillus subtilis
streptomyces
sacchromyces cerevisiae
The product labeling should indicate that the bacteria are *live*, and
may say something about how many million colony forming units are
included per unit volume, unit weight, or per dose.
Most veterinarians and lots of feed & seed stores carry paste type
probiotics. The paste type probiotics come in a tube-syringe you can use
to either squirt it into the horse's mouth or you can mix it in with
their feed. The paste type probiotics should be refrigerated at the
vet's or feed & seed store when you buy them and the pull date should not
be expired. Also, they should be refrigerated at your home until used up.
Dehydrated probiotics are another good way to replenish the horse's
beneficial gut bacteria. It is really easy to add a scoop of dehydrated
probiotics to the horse's feed every day, and is very good for the horse.
A highly recommended dehydrated probiotic is "Fastrack Probiotic Pack",
available from:
Valley Vet Supply
phone # 1-800-356-1005
website address: www.valleyvet.com
Another good dehydrated probiotic is "Opt-E-Horse", available from:
KV Vet Supply
phone # 1-800-423-8211
website address: www.kvvet.com
(They also carry the Fastrack Probiotic Pack dehydrated probiotic.)
Another source for Opt-E-Horse is:
Jeffers Equine
call 1-800-533-3377 for a free catalog.
Another supplement of this type is "Ration Plus", highly recommended by
John Lyons & crew. This supplement has no live beneficial bacteria in it,
but "encourages the growth of the beneficial bacteria, allowing the
normal (beneficial) variety to repopulate the intestines" (p. 122,
"Veterinary Care For The Perfect Horse" by John Lyons, Eleanor Kellon
V.M.D., & the
editors of John Lyons' Perfect Horse magazine).
Ration Plus can be obtained by calling 1-800-728-4667, or accessing the
Ration Plus website at: www.rationplus.com
Ration Plus is also available from Jeffers Equine, info listed above.
It could well be that the combination of a probiotic product and Ration
Plus would create an ideal environment for beneficial bacteria in the
horses' intestines.
Here are some web site addresses for those interested in doing some research on horse parasites on their own:
pfizer.com/ah/equine/equineparasite/equinep.html
pfizer.com/ah/equine/equineparasite/equestions.html
cal.vet.upenn.edu/parasit/horse/indexhorse.html
web.missouri.edu/~vmicrorc/Byhost/Equids.htm
web.missouri.edu/~vmicrorc/Drugs/Anthelm.htm
www.ces.uga.edu/pubcd/b1080-w.html
www.endurance.net/RideCamp/archives/advquery.asp
(search strings: "worm", "quest", "strongid", "safe-guard", "panacur", "ivermectin", etc.)
www.fda.gov/cvm/fda/mappgs/cvmsrch.html
(search on "horse, worm" individual drugs, etc.)
www.fda.gov/cvm/fda/TOCs/120648s42098.html
www.fda.gov/cvm/fda/infores/foi/140439/140439.html
www.fda.gov/cvm/fda/infores/foi/141087071197.html
Additional information on mimizing the parasite burden of your horses:
(the following was adapted from an article on Equine Internal Parasites
by the
University of
Nebraska )
Control and Treatment of Internal Parasites of the Horse:
Horse owners need to understand that an internal parasite control program
is a continual battle. Management practices include:
1.Feeding hay in bunks or mangers; avoiding feeding on the
ground.
2.Regular cleaning of stables and paddocks.
3.Avoiding overcrowding of pastures.
4.Avoiding wet pastures--rain, dew, flooding--especially with
young animals.
5.Not spreading manure where horses can come in contact with it.
6.Working dirt lots with a harrow, springtooth harrow, or disk to
bury manure and destroy weed growth.
7.Periodical grazing of cattle in horse pastures decreases
exposure as equine parasites do not mature in cattle and
breaks the life cycle.
Treatment programs consist of:
1.Proper drugs at the proper dosage and proper time.
2.Deworming all animals in the group or lot.
3.Deworming pregnant mares within 30 days of foaling to minimize
passage to foal.
4.Keeping lactating mares and their foals on a rigid treatment
schedule (every 6 to 8 weeks).
5.Rotating anthelmintic classes of drugs to prevent development
of parasite resistance.
Resistance generally develops with repeated usage over time.
Number of horses, space allotted per horse, age of horses, contact
between horses, type of feed (i.e. pasture or dry lot) all have a bearing
on frequency of deworming. Your veterinarian should evaluate each
individual circumstance and determine the proper drug and frequency
needed. Veterinarians can also provide fecal examinations 7 to 10 days
post treatment to evaluate efficacy of a control program.
Not only should a deworming program include using an effective dewormer,
but pasture maintenance is also important.
(the following information was adapted from an article on worming horses
by Anne Loiselle)
Despite modern science's best efforts, horsemen have yet to eliminate
internal parasites, better known as worms, which feed off horses.
However, today's deworming practices can help prevent parasites from
robbing horses of the good health.
The most common means of killing parasites is by giving horses a
deworming drug, which comes in a liquid, paste or pelleted form. Liquids
and pastes are usually given every six to eight weeks, while most pellets
are fed daily.
The number of worms can be kept to a minimum by a combination of
deworming consistently with effective products, rotating dewormers and
effective manure removal.
Probably when most people think of parasitism, they think of unthrifty
horses: You feed them but they don't look good. Additionally, a poor
hair coat may be an outward sign of damage from a heavy worm infestation.
Internal parasites interfere with the horse's ability to use nutrients
and may damage the digestive tract. Increasing the quality and amount of
feed a horse gets won't compensate for a heavy worm infestation.
The damage parasites can cause ranges from colic (the most common cause
of death in horses), diarrhea and stomach ulceration, to fever, anemia
and summer sores.
Mindful of these potential effects, the rule of a good deworming program
is to decrease contamination among horses while using a minimum of drugs.
However, not all dewormers are effective against all types of worms.
That's where reading the label on the dewormer comes into play, as well
as consulting your veterinarian.
The label lists the active ingredient that actually kills the worms, as
well as the types of worms it is effective against. Restrictions, such
as whether the product is safe for pregnant mares, should also be checked.
Go into the summer with your horses dealing with as few worms as
possible. One way to accomplish this is by spreading manure on the fields
and dragging them with a harrow to break up the manure, exposing more
worms to the elements to kill the parasites.
Worms are a problem that must be dealt with regardless of where the horse
lives. It is the temperature extremes that kill them: The cold winters
kill worms in the Northern states and the summer heat does the same job
in the Southern climates. Dewormers are most effective when used at the
peak season of infestation, which differs according to the geographic
area.
Removing manure from pastures is more effective than spreading and
harrowing the manure, . However, pasture vacuuming, as it is called, is
also far more expensive and, therefore, not as common as spreading.
Pasture rotation is another common means of controlling worms.
What you're basically hoping for is that the parasites will die while the
horses are off the field. If you don't put any stock on the field, you're
not putting more eggs on the pasture.
Ideally you would be able to rotate your horses through several different
pastures, leaving a pasture idle for several weeks or months. Another
option in the fall is to graze the horses on nearby farmland after the
crops have been harvested.
Although resistance almost guarantees that humans and horses will always
have to deal with parasites, sound management practices such as manure
removal and pasture rotation, combined with good dewormers on the right
schedule, will prevent worms from stealing your horses' health.
(the following information was generously provided by Laura Phelps-Bell
from personal notes taken during a lecture by Dr David Laird.)
According to Dr. David Laird, the vet who is an expert on encysted small
strongyles, Quest (moxidectin) in reality will only kill about 15% of the
encysted strongyles, whereas Panacur (fenbendazole) will kill a much
higher amount than that and is also a lot safer then Quest/moxidectin
(note: Panacur and Safeguard are identical products with different trade
names - the chemical name for both Panacur and Safeguard is
"fenbendazole").
Here's some notes from a lecture by Dr. Laird:
Dr. David Laird of
Texas is nationally recognized for his expertise on
internal parasite control and most recently for his work on encysted
larvicidal treatments for cyathostomiasis, a condition that leads to poor
performance and colic in horses.
Dr. Laird devoted most of his discussion to the life-cycle of the small
strongyle worm. When your horse goes out to graze in the pasture or picks
around in his stall or paddock, he is ingesting thousands and thousands
of larvae that can stay alive on the ground for up to a year. The little
larvae move along your horses digestive tract until it comes to his cecum
and colon. Then it penetrates the wall of the cecum or colon and stays
there for a minimum of 45-60 days and as long as 2 to 3 years.
Impossible, you think. You worm religiously every 8 weeks, right? There
is no way those larvae can live in there if you worm every 8 weeks.
Besides, there are plenty of wormers that kill small strongyles. Heck,
they ALL kill small strongyles. Right?
Right.....However they only kill the ADULT worms, or larvae that have not
yet burrowed into the lining of the cecum and colon of your horse. These
larvae are known as encysted larvae, and Dr. Laird likened them to a
hibernating bear. He explained that they have a very, very slow
metabolism. When you worm your horse, that wormer is in your horse's gut
for about 18 hours. Because the encysted larvae have a very slow
metabolism, the wormer simply doesn't do the job over an 18 hour period.
It doesn't effect the little guys. So, the encysted larvae sit there
making waste in the lining of your horse's gut, and when they finally
decide to emerge into your horses stomach, they leave behind all this
cellular debris, and this is when
your horse can get sick. This condition is known as Cyathostomiasis
(small stronyle infection). Symptoms can include:
Cow manure-like diarrhea
Mild reoccuring colic (2-3 days)
Listless, weak
Rapid and dramatic weight loss
Peripheral edema (swollen legs)
May or may not be eating
So you think, I'm a smart and experienced horse owner. I know when to do
a fecal egg count. Well, here's the interesting part of trying to
diagnose this condition. If you worm your horse every 8 weeks, your
fecal egg count will very likely come up a big zero -- but your horse can
still have hundreds of thousands of encysted larvae. Okay, you say you
use a daily wormer, such as Strongid C. Couldn't have "encysted larvae".
Right? Wrong! Okay you used the ivermectin, do the daily wormer every
day, except when you were at the show last month, you forgot to bring it
with you, but that was only 2 crummy days. Guess what? your horse
ingested thousands and thousands of larvae those two crummy days, and
since Strongid C only kills the larvae on the way to the cecum and colon,
once the little cuties have encysted, your daily wormer has no effect on
them. Besides, what about all the encysted larvae that were already
there before you started using Strongid C? Remember, they can live in
your horse for 2 to 3 years.
Treatment: Two times the normal dosage of Panacur wormer for five
consecutive days (note: Panacur and Safeguard are identical products
with different trade names - the chemical name for both Panacur and
Safeguard is "fenbendazole").
He explained what LD-50 means. LD stands for Lethal Dose. 50 stands for
50%. LD-50 means the dosage of medication that will kill 50% of the
animals taking it. Ivermectin has an LD-50 of 15. This means that if
you gave 10 horses 15 tubes of ivermectin wormer all at one time, it
would be likely that 5 of those 10 horses would die. Quest, has an LD-50
of only 3. So, if you gave 10 horses 3 Quest wormers, 5 would probably
die.
Well, interestingly, Panacur (fenbendazole) just doesn't kill a horse, no
matter how much of the stuff you give it. Therefore, that hibernating
baby worm that has burrowed into the lining of your horse's gut gets to
have the livin' daylights kicked out of it with a double dose of Panacur
(fenbendazole) for 5 days and it won't hurt your horse. But it will kill
all of those encysted larvae and in a nutshell, if you use Panacur
(fenbendazole) twice a year along with a regular worming program every 8
weeks, rotating the type of wormers, you will have yourself an Optimal
deworming program.
He stressed that a high performance horse will benefit tremendously from
the treatment.
*Update, 8/7/00:
According to an article by Karen Hayes (
DVM , MS , an Idaho-based equine
veterinarian) in the August, 2000 issue of Horse & Rider magazine (pp.
88-92), tapeworms should be eliminated by giving your horse 2 times the
normal dose of pyrantel pamoate (brand names: Strongid P, Strongid T,
Rotectin 2), dosage according to horse's weight, for 2 days in a row,
*or* by giving the horse 10 times the normal dose of pyrantel tartrate
daily worm medicine (brand names: Strongid C, Strongid C 2x, Equi-Aid CW,
Equi-Aid CW 2x) for 2 days in a row. This should be done twice a year,
in spring and fall, about 6 months apart.
This article also points out that fenbendazole (brand names: Panacur,
Safeguard) is the only worm medicine that eliminates *all* stages of
encysted cyathostomes (small strongyle larvae), when given at twice the
regular dose, according to horse's weight, for 5 days in a row. This
also can/should be done twice a year, about 6 months apart, perhaps 6-8
weeks before or after the pyrantel pamoate/tartrate tapeworm treatments.
In addition, information provided by Hoechst, the manufacturer of
fenbendazole, indicates that encysted early EL3 larvae typically
represent 75% of the total encysted small strongyle population in an
infected horse, and that fenbendazole is the only worm medicine available
that eliminates the EL3 larvae, when given at double the normal dose
according to horse's weight for 5 days in a row.
A side note here. Burros (donkeys) are often infected by lungworms, which
they seem to tolerate better than horses. If you bring a burro onto your
horse farm, it is advisable that you worm the burro with ivermectin
*before* you bring it onto the farm.