Well-reasoned de-worming program : fundamentals and good practices.
Nowadays, systematically treating adult horses against worms every 2, 3 or 4 months is no longer recommended as this generates worm resistance to de-wormers. The number of molecules available on the market for deworming horses is limited, and most parasites have developed resistances to these de-wormers. Here are 10 fundamentals of a well-reasoned de-worming program, as well as a review of de-worming good practices.
Do not administer de-wormers to adult horses systematically, only treat high shedders following a fecal egg-count (FEC).
Concerning strongyles, each horse should be treated according to the egg count in its droppings. A fecal egg count (FEC) determines the quantity of strongyle eggs in each horse. : there are two types of horse « high shedders » of eggs (>200-500 eggs per gram = ePG) and « low shedders » (<200-500 ePG). This parasitic status is stable in adult horses (>3 years old) for horses in good health, and living in similar conditions
20 % of adult horses are host to 80 % of parasites
20 % of horses are high shedders and are resposible for 80 % of the contamination of a given environment : these horses must be identified and treated according to a rigorous schedule.
The fundamentals of de-worming are dependant on the horse’s age
Regarding parasites, there are three categories of horse : Foals, young horses (< 3years old) and adult horses. Each different category should have a different de-worming scedule, due to the fact that immunity is established progressively. In particular, foals and young horses should be systematically de-wormed, whereas adult horses are treated according to the results of a (FEC).
It is better to wait for Spring before commencing a de-worming schedule, there is no need to de-worm in winter.
In Winter, shedding of parsites eggs in the environment is very low, so re-infestation of horses is quite low. It is preferable to de-worm at the end of Autumn, and possibly again in the Spring.
Brood mares do not need a specific treatment.
Brood mares can be treated following the same rules as the other adult horses.
Foals do not need to be treated before the age of 2 months, and 4 treatments in their first year are generally sufficient
Treat foals at 2, 4 and 6 months old, then again just before winter.
The dose of de-wormer should be adapted to each horse’s weight
The dose of de-wormer should be adapted to each horse’s weight to get maximum efficiency, but also to restrict appearance of worm resistance
A healthy horse is in equilibrium with its parasites
Wanting to rid a horse of all parasites is impossible and generates the appearance of worm resistance
A de-wormer is veterinary medication
A de-wormer can be toxic if misused, therefore it should be prescribed by your treating veterinarian.
Do not use macrocyclic lactones (ivermectine and moxidectin) more than twice a year
Parasites adapt to the mode of action of macrocyclic lactones and become resistant : it is necessary to preserve these molecules which are still efficient against strongyles.
Well-reasoned-de-worming
Good worming practices
Who prescribes the de-wormers ?
A de-wormer is veterinary drug : it should be prescribed by your veterinarian following a clinical examination, or following a sanitary assessment of the stud, this will enable the veterinarian to assess the stud’s parasitic risk, and to establish a well-reasoned approach to collective de-worming.
The choice of molecule depends on the season, the horse’s age, the results of the FEC analysis, and the previous de-wormer used. A de-wormer with drug approval for the equine species should be used. The efficiency of bovin injectable de-wormers has not been studied in horses. It is therefore not advisable to use it. Plant-based de-wormers are not veterinary medication. Their action on parasites is weak if not non-existant. It can be dangerous to use them.
Who prescribes the de-wormer ?
A de-wormer can be delivered by your treating veterinarian, or a pharmacist with a prescription. It can be dangerous to buy de-wormers on internet : there is a lot of counterfeiting, and their efficiency is unknown.
What dosage should be used ?
The horse’s weight should be estimated. Under dosing decreases the efficiency, and can generate resistances. Over dosing can be toxic for the horse.
How should the de-wormer be administered ?
1) Start by being in a quiet place
2) Make sure the horse’s mouth is empty
3) Insert the seringe at the corner of the mouth
4) Insert up to the base of the tongue
5) Lift the horse’s head up
6) Inject the paste progressiveley
7) Maintain the head up to encourage the horse to swallow
Horses in a same herd should be treated at the same time.
Know more about our authors
Translated from french by : Karen DUFFY Translator
Pauline DOLIGEZ Development engineer IFCE
Marie DELERUE Veterinarian - development engineer IFCE
Bénédicte FERRY Docteur vétérinaire - ingénieur de projets & développement IFCE
