De-worming adult horses

Here is a list of the main equine digestive parasites, with their location, the horses affected, the clinical signs, and the infestation frequency.

Small strongyles, or cyathostomins

Ascarids

Ascarids are roundworm
•    Where are they found ? In the small intestine
•    Which horses are affected ? Young horses
•    What are the clinical signs ? Weight loss, stunted growth, colic (highly pathogenic in young horses)
•    What is the infestation frequency ? Very high.

Tapeworm

Tapeworm are flat worms
•    Where are they found ? In the large intestine
•    Which horses are affected ? Horses out at grass
•    What are the clinical signs ? Colic
•    What is the infestation frequency ? Very high

Large strongyles

Large strongyles (bloodworm) are a round worm
•    Where are they found ? In the blood vessels
•    Which horses are affected ? Horses out at grass
•    What are the clinical signs ? Colic, sudden death (highly pathogenic)
•    What is the infestation frequency ? Low

Bots (Gasterophilus)

Bots are insects, their larvae infest horses.
•    Where are they found ? In the horse’s stomach
•    Which horses are affected ? Horses out at grass
•    What are the clinical signs ? General decrease in good form (low pathogenic impact)
•    What is the infestation frequency ? Very high

Pinworms (Oxyuris equi)

Pinworms are a round worm
•    Where are they found ? In the large intestine
•    Which horses are affected ? Stabled horses
•    What are the clinical signs ? Itchiness around the anus (Low pathogenic impact)
•    What is the infestation frequency ? Average

Key : + low ; ++ average ; +++ high

To control nematoda (roundworm=> all worms except tapeworm), 3 families of anti-parasitic molecules are available on the market for equines.
•    Macrocyclic lactones : ivermectin, and moxidectin ;
•    Pyrantel ;
•    Benzimidazoles : fenbendazole and mébendazole.

To control tapeworm, 2 molecules are available :
•    Pyrantel ;
•    Praziquantel.

Key : + active molecule ; +/-active but some resistances have been noted ; - inactive

A protocol for FEC and de-worming is set up with your treating veterinary surgeon. For example, in the case of a sanitary assessment of  the stud, the veterinarian can establish a parasitic audit and establish a individual protocol based on the parasitic pressure on the property, this depends on :

• Breeding practices
• Accommodation of horses (field or stabled)
• The burden
• The frequency with which the horses are moved in and out of the property.

There are two categories of horse :
    • Young horses (1-3 years of age), need de-worming systematically 3 to 4 times ayear, due to low immunity
    • Horse aged 3 or more, for which a well-reasonned de-worming schedule is highly recommnended. Ideally, a FEC should be carried out before de-worming. Only administer a de-wormer to high shedders (horses shedding more than 200 Epg in their droppings)

Each season also gives rise to the question of which molecule to use according to the targeted parasites, but also according to prior knowledge of worm resistance to the de-wormers used on the stud.

For horses aged over 3

For young horses (1-3 years of age)

Brood mares

Brood mares should be de-wormed on the same basis as other adult horses. A spring de-wormer restricts an early infestation for the foal.

Donkeys

• Lungworm (Dictyocaulus arnfieldi ) : This can provoke respiratory problems, and it can be treated with the same de-wormer as for strongyles.
• Fluke (Fasciola hepatica) : (there are rare cases, and this parasite provokes weight loss) : Fluke can be treated with triclabendazole and closantel.

Donkeys are often healthy carriers (showing no clinical symptoms) but they act as a reservoir for horses :

• They can be de-wormed following the same protocol as horses
• A preventative treatment against fluke can be considered if there are symptoms in the horses living with donkeys.