Worms

The importance of regular Worming

Worms and other intestinal parasites have always been recognised as potentially damaging to the health of horses. As we keep larger numbers of horses under increasingly intensive conditions, the danger of worms and their threat to horse health is increasing. It is therefore critical for a horse’s well being that an effective and regular worming program is maintained.

Types of Worms

Equine intestinal worms:

• Large roundworm (Parascaris equorum)Large stronglyes (bloodworms, Strongylus spp)*
• Small strongyles (redworms, Cyathostomes)*
• Pinworm (Oxyuris equi)
• Tapeworm (Anoplocephala perfoliata)
• Immature Trichonema sp., Triodontophorus sp., Strongylus vulgaris
• Bots, Hair worms, Threadworm, Stomach worms and Lung worms.

Horses are simultaneously infected with multiple parasite species, therefore a broad spectrum wormer is recommended, administered every 6-8 weeks (interval dosing).

Major Classes of Anthelmintics

There are three chemical classes of wormers (anthelmintics) currently used in equine medicine for the treatment of internal parasites.

1. Macrocyclic Lactones (Ivermectin and Moxidectin)
   – some include Praziquantel for tapeworm spectrum.
2. Benzimidazoles (BZs)
   – least used class due to known irreversible resistance^1.2
3. Pyrimidines (Morantel and prantel)
   -Comparatively less resistance documented compared to BZs³

Intensive internal dosing with these potent broad-spectrum wormers has been widely practised.

Rotation Helps Delay the Onset of Resistance

The general consensus in the equine veterinary literature is that some level of resistance to macrocyclic lactones is inevitable.¹ Thus, responsible use of equine wormers is a major issue for equine medicine.

It has been suggested that changing the chemical class of worming agent regularly will delay the onset of resistance by worms to the compounds we use to threat them. This is known as rotational worming.

“From a practical standpoint, in field situations where multiple parasite species need to be controlled, it is necessary to use more than one drug class during one year.”

A rotational worming strategy, that is, changing your class of wormer at least once a year, is the most suitable program to delay the onset of resistance.

Equiban^® (morantel tartrate) is a single entitiy wormer; it is a different class to both benzimidazoles and macrocyclic lactones which makes it the ideal rotational wormer.

* Most clinically significant worms