Internal or endo-parasites in horses are an ever present threat that might cause severe health problems, if not kept under control. There are over 60 helminthic parasite species known to choose horse as host, and a horse can be infested with several different worm species at a time. Therefore every horse should be wormed regularly with an effective antiparasitic treatment.
Why perform regular horse worming?
A scheduled, effective worming program will help to prevent your horse from severe intestinal parasitic infestation and defects in the intestinal wall and inner organs caused by migrating larvae and adult worms.
An adult worm, present in the horse's gut, lays eggs. These eggs excrete within the horse's manure, which usually ends up in a paddock, pasture or stable. Larvae hatch out of the worm eggs and expose themselves on grass. Some species occur even in dew drops! The horse ingests them during grazing and once these larvae passed the stomach, they undergo in the intestines several developmental states. Some species will first hibernate a certain time encrypted in the intestinal wall and continue on their stages of development after a defined, species-characteristic time. Other species migrate through the intestinal wall into different organs, while being in a 2nd larval phases, becoming 3rd stage larvae. Once these migrate back into the gut, they undergo a last change and become adult, mature, ready-to-reproduce worms.
A horse with a severe larvae infestation will show symptoms of fever, pain, colic, inappetence, diarrhea etc.
What needs to be done?
Very important is to manage the horse's environment, such as barn, stable and pasture/paddock. Try to pick horse manure every day and keep water sources, like troughs or buckets clean. Keep forage and horse feed in dry, appropriate storing places and perform regular pest control.
Prevention of worm infestation is the important topic within good horse health care and management:
- establish a regular horse worming schedule - include all horses on the premises - know about the grade of infestation by a random worm egg count of each horse's manure, performed by your vet. - use effective horse wormers and change products to avoid worms/larvae becoming resistant to a certain product.
How does a horse wormer work?
There are a lot of deworming products on the horse health market available: keep in mind that different worming drugs need to be used for different worm species and not all products will help to get rid of migrating larvae. This indicates the use of different dewormer. Another benefit of developing a rotating, regular worming schedule is avoidance to give parasites the chance to get resistant towards certain drugs. This would lower a dewormer's effectiveness significantly up to a point, where it will not have any effect on the parasite any more.
A horse wormer is usually administered orally to the horse. Mostly it is a paste in a convenient doser. It can also be fed as pellets or in fluid form administered via stomach tube by your vet. Injectable worming drugs are usually not used in horses, as side effects can be severe.
Modern wormers will paralyze rather than kill adult worms, so they will not release toxic chemicals which would harm the horse and they are unable to resist being excreted with the manure. Outside its host, an intestinal worm will die.
The time between a worming treatment and the reoccurrence of eggs in the manure is called "Egg reappearance period" or ERP.
If the specific ERP of a worming product is being exceeded (e.g. you forget to worm regularly within the recommended time range for the product), the worm egg count will increase and again, more worm eggs will spoil the pasture and grazing and finally the horse will start ingesting increasing numbers of larvae.
Ideally consult your vet and work out a decent and effective horse worming plan customized to your individual situation.
Disclaimer: All information on this site is provided for informational purposes only! By no means is any
information presented herein intended to substitute for the advice provided to you by any health care or other professional
or organization.
