Post by Calaminty Jane on Jan 31, 2009 12:43:15 GMT -5
How to Control Parasitic Worms
What is a Parasitic Worm?
Gastro-intestinal parasites (worms) affect all horses and ponies and include various species of nematodes (which are slender segmented worms). The definition of a parasite is an animal or plant living in or on another and drawing nutriment directly from the host.
Parasitic worms damage the intestines, as they attach to the inside of the gut, suck blood and burrow through the body of the host during the migratory part of their life cycle.
The Life Cycle Of A Worm
The eggs, which are passed out in the dung, undergo a period of incubation of several days. The infective larval stage hatches from the egg, under ideal conditions this is within about a week. The larvae migrate in the water film over the surface of the plants and spread themselves through the grass around the droppings. From here, a suitable host (e.g. your horse) must eat them. They can then develop into the adult worm.
Development of most species is slowed or halted by winter temperatures, (assuming we have some cold weather and frosts). Dry weather causes the death of some larvae and their movement to edible grass is slowed without the water film on the grass.
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Reducing The Worm Burden
Environmental and management factors can directly influence the development and survival of the worm population on the grass. Combined with an efficient worming programme, this can greatly reduce the threat of harmful parasitic infestation.
One way to reduce the worm burden it to start with a 'clean' pasture, this is especially important when the larvae population is high, during the spring, summer and autumn. Large numbers of larvae on the grass coincide with the best growing conditions for grass (warm and wet). This is when most horses spend the majority of their day grazing.
Land that has not been grazed since the previous autumn and has been harrowed, rolled and fertilised, then been cut for hay/silage is the 'cleanest'. If the grass is grazed in the spring, then topped, harrowed and fertilised; left to rest for 6 weeks and then grazed by cattle or sheep this will also help to reduce the worm problem.
Cattle prefer longer grasses and are therefore more suitable to graze with horses than sheep; they will also eat grass that horses avoid. Sheep will eat the docks but graze the grass very short. Larvae eaten by cattle or sheep will be destroyed as both cattle and sheep are ruminants.
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Picking up dropping from the paddock is vital, this job should be done at least twice a week, but daily is more advisable and also less of a chore. Two horses in a field skipped out daily take about 20 - 30 minutes, plenty of time to observe your horse.
Worming your horse 24 hours before turning out into fresh pasture will also help to keep the paddock 'clean', and making sure that you collect all the dropping produced will greatly reduce the worms in the paddock.
When purchasing a new horse, keep him/her isolated from any other horses until your vet has done a faecal count and the horse has been wormed accordingly.
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Finding Out About Your Horse's Worm Burden
By counting the number of eggs in a few balls of dung your veterinary surgeon can find out about yours horse's worm burden. The vet can then advise you as to how much and of what brand of drug to use to eliminate the worms. Subsequent egg counts done 10 to 14 days after the initial treatment will reveal whether the treatment has been successful or whether the worms have developed a resistance to the drug used.
Resistance occurs partly because owners worm without expert advice, using incorrect amounts of drugs and at the wrong intervals. This creates a breed of resistant 'super-worm' that can cause major problems.
The parasitic worm has a very efficient life cycle and has been around for as long as there have been horses. We cannot eradicate the worms' only keep it under control with good pasture management and regular doses of anthelmintic wormers.
Worming Diary
Horses should be wormed every 6 to 12 weeks. A wormer has yet to be invented which treats all parasites, so it is very important to work out an annual routine incorporating different wormers with your Veterinary Surgeon.
The following is an example worming chart based on horses in the UK .
Before worming your horse it is advisable to consult your veterinary surgeon about suitable doses, which are dependent on the weight of the animal and the type of wormer (anthelmintic). Knowing your horse's weight is vital when worming. Manufacturers advise horse owners to check the weight of their horse, either by using a weighbridge or, by using a girth measuring tape, before deciding on a suitable dose.
Do not simply go on height and build; a 16hh Thoroughbred will be a different weight to a 16hh Irish Draught.
Powder Or Paste
Anyone who has ever attempted to worm a horse knows how difficult it can be despite manufacturers devising numerous ways to make the medicine palatable.
Granules, powders or pellets can be mixed with a horse's feed but you need to keep a close eye to ensure the entire dosage is eaten. Many horses will careful separate their feed from the wormer, leaving the drug in the bottom of his bowl.
Alternatively the wormer can be given in the form of paste by oral syringe. Worming in this way is an art if you are not going to end up wearing most of the paste.
Chemical Groups - Commercial Wormers
Every wormer contains one of five ingredients, namely Pyrantel Embonate, Ivermectin, Moxidectin, Mebendazole and Fenbendazole (one of the Benzimidazole group). So look on the packet for the ingredient when buying a wormer.
Detailed instructions are included with each medicine, we therefore recommend you always read the package labelling or leaflet within the pack, before using any product. The worming drugs currently available for use in horses are extremely effective. However, horse owners should realise that individual drugs only treat certain worms and that some drugs only treat some of the life-cycle stages of certain worms.
A further complicating factor is that some worms have developed resistance to certain worming drugs. The more frequently worms are exposed to the drug, the greater the chance of resistance developing. It is not as simple as giving a dose of wormer and all the worms are killed!
Tapeworms
Bots
Encysted Small Redworms
Migrating Large Redworms
Strongid P
Panacur Equineguard
Panacur Equineguard
Pyratape P
Equest
Equest
Equest
Eqvalan
Eqvalan
Furexel
Furexel
See worm cycle for more information on worms.
Only two wormers can kill hibernating small red worms, Equest and Panacur Equine Guard. All worm programmes should include at least one treatment with one of these per year.
You may also find it useful to have a worm count done on your horse's droppings. These are inexpensive and will give you a good idea of how effective your worm control is.
Mares in Foal
No extra anathematic treatment is needed for the mare as long as she is included in a sensible control programme but it is always advisable to consult your Veterinary Surgeon. However, to reduce her output of worm eggs which her foal may then consume she should receive an additional dose of Ivermectin approximately 4 weeks before foaling.
Foals
It is very important to worm foals at 4-6 weeks with Ivermectin then every eight weeks, before the worms reach maturity. Do not administer Equest to young foals less than 4 months of age.
New Horses
Introduced to a yard should be wormed with moxidectin and kept in a box or restricted paddock for a two days with collection and disposal of droppings prior to any introduction to communal pasture. This should be followed by a five-day Fenbendazole course to treat any inhibited and remaining encysted small redworms present. These horses should also be blood tested for tapeworms and treated with "double-dose" Pyrantel P or Strongid P depending on the results. Monitor faecal egg counts every three months initially to ensure your programme is adequate.
Your worm control will only be as good as your grassland management. Picking up droppings in the field, daily, not allowing the ground to go ‘horse-sour’ and keeping weeds at bay are essential. Rotating cattle or sheep after the horses have grazed the land and ploughing, liming and reseeding every few years will help prevent worm infestation on the pasture.
Note: Wormers are constantly being developed and you should always consult your veterinary surgeon for personal advice for your horse in your region.
How To Administer Anthelmintic Drugs (Wormers) To Your Horse
There are several different internal parasites with varying life cycles that infect our horse. The worms are picked up the horse licking eggs off his forelegs (Bots) or eating larvae with infected grass.
The worms fall into three categories: -
* Flatworm - these live in the horses bowel.
o Liver Fluke
o Tape Worm
* Roundworms - these migrate through the internal organs, liver, lungs and blood vessels
o Seatworms
o White worms
o Redworms (both large and small)
* Bots - these migrate through the internal organs, liver, lungs and blood vessels .These not truly a parasitic worms. It is an insect that lays its eggs on the horse's legs, and the horse licks off the eggs. Once in the mouth they burrow into the tongue and gums to develop into larvae - these migrate to the stomach. Here they attach to the stomach wall to mature 'over winter'. In the spring, the crystalis is expelled with the dung and hatches into an insect known as a gadfly.
All horses suffer from some form of parasites. So that we do not spend money on feeding parasites is essential that the horse be wormed regularly. Treating the horse with an anthelmintic drug that kills the parasites can do this and some 'wormers' even prevent worms re-infecting the horse for several weeks.
The worm cycle and burden page has more information on the wormsand the worming diary has information on the types of wormer..
1. Tie up your horse. Make sure his mouth is empty, a ball of food at the back of his mouth will make it much easier for him to spit out the paste.
Ensure that your horse approves of his wormer!
2. Insert the syringe into the corner of the horse's mouth at an angle of about 45 degrees to his head, (there are no teeth there).
Open Wide!
3. Gently push the syringe into the horse's mouth and push the plunger. Wiggling the syringe around the mouth to spread the paste across his tongue. One large lump of paste is very easily spat out.
All Gone!
4. Lift the horse's head as you depress the plunger to encourage the horse to swallow the paste and keep his head up until he has swallowed the paste.
5. Check the syringe is empty to ensure the horse has had the correct dose. Any paste left in the syringe repeat steps 2 to 4.
How To Give Anthelmintic Granules To Your Horse.
1. Make up your horse's usual feed.
2. Sprinkle the powder into the middle of the feed and stir lightly to spread the powder through the feed. If you stir the feed too vigorously the worm powder will end up on the sides and bottom of the bowl and therefore the horse not receive the full dose.
3. Give the feed to the horse in the usual way and ensure that all is eaten before giving the horse any further food. Some horses are reluctant to eat worm granules - it may be necessary to add a little more feed to encourage the horse to finish the meal.
It is critical that the horse is wormed at the correct dose for his weight and height. Under treatment can lead to the worms becoming immune to a particular brand of treatment, thus producing a 'super-worm'.
If in any doubt consult you veterinary surgeon who will advise you.