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Health Features | |||||||||||||||||||||||||
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The Horse |
Parasites - Worms | |||||||||||||||||||||||||
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Small Strongyles
(small redworms) Cyathostomes
Can cause severe damage to the gut
leading to weight loss and diarrhoea and colic
Large Strongyles
(bloodworms)
Strongylus vulgaris, S. equinus, S. edentatus
S. vulgaris cause severe damage. Migrating
larvae rough up artery walls, leaving tracks where blood clots can
form. Clots break away from the wall and lodge into other blood
vessels, blocking blood flow to the intestine. Artery walls weakened
by larval damage are also prone to burst, leading to immediate death.
In the large intestine, large strongyles literally bite off pieces of
flesh, often leading to severe colic, diarrhea, fever and anemia from
the bleeding bite wounds. S. equinus and S. edentatus
can cause liver damage.
Neck Threadworms Onchocerca cervicalis
Adult neck threadworms in the ligaments and tendons
cause swelling and pain. Microfilariae may invade the lens of the eye,
causing irritation, swelling and sometimes blindness. Microfilariae
under the skin may cause irritation.
Intestinal Threadworms Strongyloides westeri
Threadworm larvae in the lungs can cause bleeding and
respiratory problems. The worst damage often occurs in untreated foals
who can suffer diarrhea, weakness, weight loss and poor growth.
Pinworms
oxyuris equi
Live in the large intestine and can
damage the bowel wall. Heavily infected horses may be nervous
and stop eating. The severe itching makes the horse rub its tail and
rump so much the tail hairs break off. Rubbing, biting and scratching
can open up the skin to infections.
Tapeworms
anoplocephala perfoliata
Cause weight loss and chronic
diarrhoea and sometimes colic. Severe tapeworm infection can cause
intestinal irritation. Fatal intestinal blockage can occur as worms
accumulate at the ileocecal junction - the 3-way junction between the
small intestine, large intestine, and cecum.
Ascarids, Round Worms
parascaris equorum
Ascarids are especially dangerous to foals aged 6
months or younger. Severe infection in horses this young can build up
quickly and lead to liver and lung damage, poor growth and even death.
Larvae in the bloodstream can cause coughing, fever, pneumonia,
bleeding lungs and respiratory infections. In the adult stage,
ascarids live in the small intestine where they can cause colic,
blockage, ruptured gut and death.
Hairworms
trichostrongylus axei
Cause gut damage,making the horse unable to digest and
absorb nutrients properly. Dark, foul-smelling diarrhea may result.
Severe damage can cause bleeding into the intestine, leading to anemia
and loss of condition. Foals are particularly susceptible to hair worm
infection
Lungworms
dictyocaulus arnfieldi
Lungworm larvae irritate the small air sacs in the
lungs, called the bronchioles, which can cause the horse to have a
severe cough, difficulty breathing and loss of appetite. Infection is
usually light in older horses because they develop resistance to the
parasite and usually have no signs. If foals are infected, they could
die from a lungworm infection because they have less immunity.
Bots
gastrophilus spp.
Adult females deposit eggs on the horse's legs,
shoulders, chin, throat and the lips.The horse licks yellow eggs laid
by G. intestinalis on its forelegs and shoulders. The eggs hatch and
enter the horse's mouth. G. nasalis lays eggs around the horse's chin
and throat. These eggs hatch and the larvae burrow under the skin to
the mouth, wandering through the mouth before migrating to the
stomach. Bots can cause inflammation of the mouth and stomach
irritation. Severe infestation can cause intestinal blockage, often
leading to irritation, ulcers and colic.
The redworm is fairly typical of
the nematode parasites and has 5 stages in its life.
1. Larvae are eaten by the horse
2. Once swallowed, lavae are passed
into the gut.
3. The lavae burrow into blood
vessels and move into the main arterial root, where they develop into
adults.
4. The adults return to the
intestines to lay their eggs.
5. The eggs are passed out of the
horse's body in it's droppings, ready to start the cycle again.
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Nutrition |
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Some of the symptoms of worm
infestation are very generic and may indicate a number of other
problems. If in doubt consult your vet for help.
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There are a wide variety of worming
drugs on the market which may treat either single worm types or a
variety. Worming programs should be planned and carried out
rigorously to effectively protect your horse. There's little
point in dosing up your horse only each time you notice an
infestation, as this will mean that your horse's gut and health may be
being damaged each time. Instead have a regular worming regime
which treats all worm types around the year and takes into account
your horse's constitution and the prevalence of worms in your
paddocks. (see the
section on precautions)
Tapeworms, for instance, can infect
all year round and may require double doses of wormer every six months.
Redworms on the other hand may be best treated in the Autumn, and early
spring with a 5 day course of fenbendazole. Bots will require ivermectin
or moxidectin based products. There are also multi-wormers which
provide protection against a wide range of parasites but which require
dosing every 4 -13 weeks (dependent upon the product) all year around.
Horses housed in a paddock or large yard should be wormed every 6-8
weeks, as they are more likely to become re-infested with worms while
grazing. It is important to remember that up to 99% of worm larvae exist
on the pastures and only 1% are actually in a horse
Rotate chemical types of product for your general worming program to help reduce resistance. This is especially important if you choose to use any of the multi-wormer products. A list of chemical types and their brand names is shown below. (check packaging for the most up-to-date information) Using mixtures of drugs (from 2 different families of worming products) has also been recommended to slow the development of resistance. For example, Strategy-T Paste contains a combination of Oxfendazole and Pyrantel that work together synergistically, achieving a much higher efficacy against redworms than when either drug is used alone. Strategy-T is proven to be highly effective against BZ resistant redworms.
Always give the correct dose. Modern worming products are
usually safe compounds - it is better to slightly overdose than to
underdose. Underdosing increases the risk of selecting for resistant
strains of worm. If possible horses should be weighed before worming or
their weight estimated with a heart girth tape to ensure that their
weight is not underestimated.
Be careful to avoid horses spitting out paste wormers and
therefore only receiving a part of their dose. Deposit the paste over
the back of the tongue, not between the cheeks and the teeth, which
makes it easier for the horse to "slobber" the dose out. After dosing,
hold the horse's head up for 15-20 seconds and rub the throat latch area
to stimulate the swallowing reflex.Always
follow the instructions for the product in use and consult with your vet
if you are unsure. If using granules or powders which require
multiple doses in feed, make sure that the horse eats all of the feed
and worming powder. Fedding in chaff or a feed that horses
frequently 'throw around' will reduce the chances that the horse will
receive the correct dosage.
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The chemical names for wormers are shown here with the
Brand Names that they are sold under on the right hand side.
Remember when rotating wormers that you should rotate CHEMICAL every 2-3
years only.
Chemical - Brand Name(s)
Pyrantel Pamoate - Strongid-P,
Strongid Caramel, Pyratape P, Rotation 2
Pyrantel Tartrate(daily) - Continuex,
Strongid C
Pyrantel Tartrate (single dose) -
Manna Pro, Purina, Kaeco
Benzimidazoles (Fenbendazole) -
Panacur, Panacur Equine Guard, Equitac, Telmin, Lincoln, Equivurm
Oxfendazole - EQUI-CIDE®;
BENZELMIN® SYSTAMEX
Oxibendazole - ANTHELCIDE®EQ3
Moxidectin - Equest (QUEST) -
please refer to the article on
Premarin before choosing this brand
Ivermectin - Eqvalan, Furexel,
Panamec, Equimec, Rotation 1, Eraquell
Abamectin - Valuemec, Equell
Morantel Tartrate - Paraminth,
Equiban
Praziquantel - Droncit, Cestex - used in combo wormers for tapeworm
eradication. *tapeworm resistance to this chemical is becoming
widespread in human tapeworms
Multi- Chemical Wormers - Praziquantel is added to kill Tapeworms
making these complete wormers*
IVERMECTIN and PRAZIQUANTEL -
Abamectin and Praziquantel - Equitak ALL, PROMECTIN PLUS, Genesis *Note: Although these are 'complete' one-dose wormers there is not a single wormer on the market which kills ALL worm types. Many cannot protect against encysted red worms Or will only protect against one type of tapeworm. |
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Alternative
remedies can be used as worming programs. Like most natural
remedies however, this will involve more of your time in research and
monitoring (you will need to regularly perform egg counts) to be
effective. However, if your horse reacts badly to conventional
wormers or if you wish to avoid chemicals or if your horse has
particular constitutional weaknesses you may like to try alternative
treatments for worms.
Redworms - wormseed (Cina), snake
head (Chelone)
Tapeworms - Male fern (Flix mas),
granatum
Pinworms - wormseed
Ascarids - wormseed, Cina extract,
Cat thyme, sodium phosphate
Results from the herbal worming products are often patchy
- a single herb being effective only against a single worm type at a
particular time in it's developemental cycle.
Tobacco has been traditionally used as a herbal wormer -
unfortunately it is ineffective. In order to kill any parasites
you would need to feed it enough tobacco to kill the horse!
Diatoms, or Diatomaceous earth is another recently
popular 'natural' product purported to have deworming properties.
Unfortunately, there is absolutely nothing natural about a horse
ingesting what could also be described as natures equivalent to
asbestos! Diatoms have never been safely tested as a wormer for
horses, there is no known safe dosage, are not effective against lung
worms and could cause severe health effects on you or your horse's lungs
if you beath them in.
Worm Counts
When using any worming program and
particularly natural worming treatments you can keep a track of the
effectiveness through the use of 'worm counts'. This usually
involves taking a sample of your horse's droppings and sending them off
to a laboratory where the numbers of eggs, lavae and adult worms are
examined using a microscope.
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Preventing and reducing large
infestations can help you reduce the number of times that you need to
worm your horse and generally improve your horse's natural health.
This means pasture and stable management which will help to reduce the
risk of infestations being passed from one horse to another and break
the life cycle of the worm.
Resistance to Chemical Wormers The macrocyclic lactones or "mectin" family (any product ending in 'ectin') of worming product is the most common class of wormer used in Australasia today, including Equimax (abamectin), Equimec (ivermectin) and Equest (moxidectin). These are very good worming agents however, "mectin" resistance has already developed in some strains of sheep, cattle and goat parasites and it is feared that horse parasites may eventually be affected. Fenbendazole resistant worms are well documented in the Northern Hemisphere. How can resistance be avoided? To avoid or slow the development and spread of resistance particularly to the "mectin" products:
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Internal Parasites of Horses
R. Bruce Hollett, Extension Veterinarian - Equine
Horsemen's Laboratory
- Dr. John Byrd, DVM
Owner and President
Prevention of Equine Colic
by Judith A. Reynolds, Ph.D.,
P.A.S - discusses Ascarid worm impaction
Controlling Parasites in Foals and
Horses By Sarah
Probst University of Illinois College of Veterinary Medicine
Farnham Pharmaceuticals guide to Equine Parasites - NOTE Although
this gives good information on worms, their life cycles and the problems
they cause this site will not mention all chemicals on the market,
Farnham products will feature highly.
Ecological Agriculture Projects, McGill University (canada) THE CONTROL OF INTERNAL PARASITES IN RUMINANTS - although not specific to horses this article contains much excellent information about the wide variety of worming practices
04-Jul-2007 Contact the Webmaster Discuss this Page |
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