Student Workbook
H1.8 Parasite Control
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H1.8ParasiteControl
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Student Number: ………………………………………………………….
Email: ………………………………………………………………………
Phone: ……………………………………………………………………..
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H1.8ParasiteControl
Contents
Parasite Control Introduction
Pg. 4
Life Cycle of a Worm
Pg. 5
Common Internal Parasites
Pg. 6 – 8
Effective Parasite Control Measures
Pg. 9
De-Worming
Pg. 10 & 11
Using a Paste Wormer
Pg. 12
Extension Lesson
Pg. 13
Recommended Reading
Pg. 14
References
Pg. 15 & 16
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H1.8ParasiteControl
Parasite Control Introduction
Parasites are organisms which live in or on a host (i.e. horse) and gains nourishment from
the host. That means that viruses, bacteria, fungi are all parasites however in this workbook
worms will be covered.
Effective worming strategies and management practices will help to keep you horse and
paddocks or pastures healthy.
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Life Cycle of a Worm
Each type of worm will have a slightly different life cycle in regards to how long the process
takes and where they will end up in the horse’s body however the overall cycle is the same.
Adult worms already present in the horse lay eggs
which get passed out in the manure.
The contaminated manure is passed onto the
pasture with the worm eggs
The eggs then hatch into larvae on the pasture
Whilst grazing the horse picks up and ingests the
larvae which then migrates to wherever that
particular type of worm inhabits in the horse’s body
systems
The larvae mature into adult worms, which lay eggs
and the whole process starts again.
The life cycle of a worm can be subject to seasons (climate, weather). Some worm eggs will
only hatch under certain environmental circumstances (i.e. warm weather) or at a certain
time of year.
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H1.8ParasiteControl
Common Internal Parasites
The vast majority of horses have worms and there are a few different types, all of which will
affect different body systems. Below are common types of internal parasites you will be
worming against.
Strongles
There are large and small strongles and they are also referred
to as redworms and bloodworms. These worms burrow into the
walls of the blood vessels. Heavy burdens can cause death and
they are also a common cause of colic.
Blood clots form from where the larvae have buried into artery
walls, these blood clots then break away and can clog up
arteries which can lead to the intestines or hind legs.
During infestations, these parasites may become visible in
water troughs and in manure.
Pin worms
Found in the large intestine, here they can cause ulceration, the
eggs are released into the rectum and anus which causes
irritation to the horse. This can be apparent from the horse
rubbing its tail. The eggs are then transferred onto pasture or
water.
Severe infestations can cause anorexia and nervousness.
Chronic infections will lead to horses which are poor in
appearance.
Thread worms
Most likely found inhabiting the small intestine of foals up to 6
months of age. They are transmitted to the foal through the
mares milk. They are uncommon after that age.
Diarrhoea, dermatitis and weakness are signs of infestation and
in severe cases death.
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Common Internal Parasites (cont.)
Bots
a.
b.
There are bot eggs and bot flies. One leads to another. Bot
flies lay bot eggs on the hairs on the horse. The eggs are
small and yellowish in colour, the flies are large an sometimes
look like bees. The horse ingests the larvae when it rubs
against the eggs with its mouth. The larvae remain in the
mouth for 1 month before migrating to the stomach where
they can cause haemorrhage, intestinal blockage, ulcerations
and perforation of the stomach. Here they will stay for 12
months living off tissue and blood. Then they are passed out
in manure where they will pupate and emerge as flies and the
process starts over.
a.- eggs
b.- fly
Roundworms (ascarids)
Common in young horses they can cause coughs, rough hair,
slow growth and pot bellies. Of course in large numbers they
can cause death.
These worms are carried to the blood supply to the lungs
where they break through blood vessels to migrate into the
trachea. Here they are coughed up and swallowed again to
end up in the small intestine, where they mature. Strangely
enough this is where the process starts because to gain entry
into the blood stream they first burrow through the intestinal
wall
.
Onchocerca
The microfilariae (early larval stage) of Onchocerca are found
just beneath the skin. They can invade the eye and cause
blindness and the adults are found in the neck and flexor
tendons. They can cause skin lesions along the belly, chest
and sometimes head (which are irritating and itchy) and
heavy infestations can restrict movement. Adult Onchocerca
can cause swelling or lameness in the front legs if they get
into tendons or suspensory ligaments.
They are spread through biting midges which transfer the
microfilariae by biting an infected horse then biting a non
infected horse.
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Common Internal Parasites (cont.)
Tapeworms
Tapeworms take up residence in the digestive tract. When
the end of the worm fills with eggs, it separates and is
expelled from the body in manure. They can cause colic, poor
growth and lethargy
Most of the damage inflicted by worms is internal however there are some visible signs
which may indicate an infestation.
Signs of worms or the need for worming may include:-
-
itchy tail
poor coat condition
loss of weight
poor weight gain
presence of worms in manure or water troughs (redworms)
summer sores
diarrhoea
lack of energy
hair loss
colic
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Effective Parasite Control Measures
Within your management of your property or paddock there is some effective management
practices you can do to help minimise worm populations. Small properties and paddocks are
more likely to have higher populations due to high stocking rates in a small area (i.e. many
horses on a small piece of land). This doesn’t mean the operator of the small property is
negligent or irresponsible in their horse care, it is just that where there is a higher population
of horses there is more likely to be a higher population of worms.
1) Other than regular worming schedules there are a few more things you can do to
help control parasites.
2) Picking up and removing manure as often as possible. Small areas such as stables
and yards can require manure removal twice a day while in larger areas removal at
least twice a week. Completely clearing a paddock of manure will reduce the number
of eggs in the paddock therefore reduce numbers of reinfestation.
3) Prevent overgrazing by reducing stock numbers on pasture. More horses mean more
manure which means higher contamination.
4) Keep feed off the ground. Put feed and hay into feeders.
5) Cross graze (to alternate grazing of paddocks between species) paddocks with
sheep or cattle. By cross grazing it will interrupt the life cycle of equine parasites.
6) Spell (give the paddock a break from grazing) paddocks regularly. Mowing and
harrowing pasture whilst giving the paddock a ‘rest’ will break up manure piles and
expose eggs to the environmental elements.
7) Remove bots eggs from the horse’s coat. Knives are available designed specifically
for this purpose.
Your veterinarian will be able to do faecal egg counts which will help you to be able to
monitor the effectiveness of your worming program.
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De-Worming
There are many different worming products on the market. Worming compounds are
available in paste or powder/granules form.
Pastes come in a plastic syringe and are inserted into the mouth over the back of the tongue.
This type of compound can be brought from your local saddlery, produce or stockfeed store
and is quick and fairly straight forward to deliver.
Powders or granules are mixed in with the horse’s daily feed. It is a less common method or
delivering worming compounds. Some horses may sift the product out of the feed.
There is another method of delivering wormer and that is by stomach tube by your
veterinarian. This method delivers the compound straight to the stomach and is used mostly
for horses with heavy infestations. It should only be performed by a veterinarian.
You will need to rotate wormers regularly. This means choosing and alternating between
wormers of different chemical compounds to ensure that the parasites don’t build up a
resistance to one particular compound because they are always exposed to the same one,
which will make the worming product ineffective. Some wormers will only treat certain
parasites and at certain times of the year various parasite groups will pose a threat more
than at other times of the year.
Over dosing with wormer to ‘be sure’ is not necessarily a good idea. It have serious health
affects for the horse. Under dosing can lead to a build up in resistance to the product by the
parasites, simular to the resistance mentioned when worming compounds/wormers aren’t
rotated. Under dosing resistance is built up because the dosage of the chemical agent is not
strong enough to kill the parasites.
Therefore it is important to establish the correct weight of the horse to be wormed (or dewormed). This can be done without scales by using a weight tape.
Weight tapes usually have instructions on how to use them imprinted on the tape but to give
you an overview you measure the length of the horse, from the point of the shoulder to the
point of the buttock. The second measurement is taken from around the girth so the tape
should lie just behind the wither and behind the elbow.
Then calculate the two measurements by:[Girth (cm) × Girth (cm) × Length (cm)] / 11,900 = Weight(kg)
[Girth (in) × Girth (in) × Length (in)] / 330 = Weight (lb)
It is important that the horse be standing still, on level ground and fairly square (the 4 hooves
placed so that they would illustrate the 4 corners of a square or rectangle) to get an accurate
measurement.
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De-Worming (cont.)
There are some other factors which will influence the type or brand of worming product you
use. Some wormers will be unsuitable to use on foals, pregnant and/or lactating mares and
breeding stallions. It is a good idea to check the label on the product before purchasing or
you can consult your veterinarian.
How often you worm your horses may depend a little upon your situation. A horses kept on
large acreage by itself may require treatment less often than a horse kept in a smaller
paddock or with numerous other horses. This is because the horse kept in the smaller area
or with other horses will be exposed to worms in larger numbers.
Weather will also play a part horses in climates where it is hot and humid may require
worming every 6 weeks.
As a general rule horses which are kept on their own in a small paddock will require worming
(de-worming) every 6 – 8 weeks.
Check the labelling on the worming product. The label will specify:-
how long it will stay active in the horse’s system before you need to de-worm again
what horses it is safe to use on (i.e.- whether it is suitable for pregnant mares etc)
what worms and parasites it works on
what chemical it contains (useful knowledge for when you are rotating wormers)
when to administer (i.e. before feeding or after feeding)
If in doubt consult your veterinarian.
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Using a Paste Wormer
How to administer a paste wormer:1) Restrain the horse with a halter and lead rope, if necessary you can have an
assistant hold the horse
2) Measure the dosage required for that horse
3) If you have no assistant you will need to hold the lead rope whilst you stand to one
side of the horse’s head
4) Insert your thumb into the corner of the horse’s lips. Remember there are no teeth in
this area and by inserting a thumb or finger into this area will encourage the horse to
open its mouth
5) Make sure the mouth is free from feed and grass. The best way to avoid this is not to
worm immediately after feed times. If there is any food in the horse’s mouth it will
mean that when you administer the wormer it will get onto the feed and the horse will
spit it out resulting in the horse being under-dosed. Usually the horse will spit out any
feed when you use your finger to in the corner of the lips to open the mouth. Do not
attempt to remove feed from the mouth with your hand or fingers!
6) Insert the syringe into the corner of the mouth and aim it upwards towards the back
of the tongue
7) Depress the syringe
8) Remove the syringe and raise the horse’s head. This is to help prevent the horse
from spitting it out and encourage the horse to swallow
9) Finally release the horse
10) Dispose of the syringe as described by the labelling on the product
Some horses may be more difficult than others, if so handling the horse in a smaller yard
can be effective in helping to control them.
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Extension Lesson
How often do you or your establishment de-worm your horses?
……………………………………………………………………………………………………………
Ask another horse person about how frequently they de-worm their horses and why they deworm in that time frame.
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Is there a type of parasite in your horse keeping facilities that are in abundance?
……………………………………………………………………………………………………………
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If so, how do you manage and minimise the parasite?
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What wormers or products do you or your establishment use when rotating wormers?
…………………………………………………………………………………………………………….
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Recommended Reading
Publication:-
Author:-
Feeding and Nutrition of Horses
John Kohnke
Foot Steps
Sally Hinton & Joan Ecclesshare
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References
Publication:-
Author:-
Feeding and Nutrition of Horses
John Kohnke
Foot Steps
Sally Hinton & Joan Ecclesshare
Storey’s Guide to Feeding Horses
Melyni Worth
The BHS Veterinary Manual
P. Stewart Hastie
Veterinary Notes for Horse Owners
Captain M. Horace Hayes
Websites:http://www.acreageequines.com/horsecare/horsecare4.htm
http://www.uky.edu/Ag/AnimalSciences/pubs/vet32.pdf
http://www.localriding.com/worms-life-cycle.html
http://en.wikipedia.org/wiki/Microfilaria
Images:Page 5
http://au.merial.com/disease_information/horses/imagefolder/endo_draw_pg_8.gif
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www.squidoo.com/EpicFarmsColic
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website.markjohnstonracing.co.uk/?page=10574
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www.farnamhorse.com/.../int_threadwrms.php
Page 7
www.abbeydiagnostics.co.uk/news.htm
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www.sxc.hu/photo/1204962
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www.valleyvet.com/si_worm_facts.html
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www.merckvetmanual.com/mvm/htm/bc/30401.htm
Page 8
www.horsebc.com/kvs/worming.htm
Page 9
http://pepaproject.googlepages.com/cowsgrazing.jpg
www.landscapejuice.com/.../putting-the-gra.html
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References (cont.)
Images:Page 10
http://img.smartpak.com/product/15805.jpg
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http://www.jareta.co.uk/Assets/Jareta-Stud-pregnant-mares-.gif
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http://www.quaintonstud.co.uk/images/FoalSuckling.jpg
http://www.worldclassstallions.com/images/koen%20web.jpg
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http://wormersdirect.com/images/library/images/worming_a_horse.jpg
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