Cinque Ports Veterinary Associates

Worms remain the most common everyday threats to horse health.  Traditionally worm control has been carried out using chemical means.  However, given the recent launches of new wormers, a fresh look is needed for worming programmes.

Non-chemical methods of worm control

1. Picking up droppings from pasture:  More than 99% of the worm population is on pasture and only less than 1% in the horse.  Twice weekly droppings' collection has proved to give better worm control than chemical treatment.  However, this may not be possible during periods of bad weather.

2.Harrowing and topping in hot dry weather is very effective in killing worm larvae.  Weather conditions prevent this method from being used more commonly.

3. Mixed grazing with sheep/cattle will reduce the numbers of horse worm larvae on a pasture.  The vast majority of sheep and cattle worms are not transmissible to horses.

4. Non-intensively grazed (less than one horse per acre) horses can be monitored using regular worm egg counts to assess the need for worming.  This does not warn however when worming is due against encysted redworms and tapeworms.

Chemical methods of worm control

1. Control programmes should be tailored to the individual needs of each establishment and should be monitored by periodic worm egg counts.

2. Annual rotation of wormers should be practiced between the three chemical groups (A - Panacur, Equiverm, Telmin, B - Pyratape, Strongid, C - Eqvalan, Furexel, Equest), e.g., use one wormer from group A for year one, one from group B for year two and one from group C for year three.

3. Tapeworm treatment at least once and preferably twice a year in March and September.  We would recommend Equimax for this treatment as it is more effective than its competitors.

4. Encysted small redworm larvae should be treated in November with a five day course of Panacur Guard.  Intensively grazed horses should be treated again in February with Panacur Guard.

5. Bot treatment should be undertaken in December with one of the group C wormers (e.g., Eqvalan).

6. New arrivals to the yard should be treated with a five day course of Panacur Guard followed by Equitape one week later.

7. It is advisable that all horses in a yard are treated at the same time.

Which are important worms and which drugs are effective against them?

1. Small redworms are currently the major internal parasite causing disease in horses.  They hibernate (encyst) in the wall of the intestine which reduces the absorption of food and causes a severe diarrhoea when they emerge from hibernation.

2. Large redworms were a major problem twenty years ago due to migrating larvae which blocked intestinal blood vessels leading to colic.  These have become much less problematic since the advent of Eqvalan, Furexel and Equest.

3. Tapeworms were once thought to be harmless but are now recognised as a cause of colic.  Tapeworms have traditionally been treated with a “double” dose of Strongid or Pyratape P.  However, there are now  new much more effective tapewormers available at a standard dose rate - Equimax or Equitape

Recommended treatment intervals

Equest (moxidectin) 13 weeks

Eqvalan/Furexel (ivermectin) 8 weeks

Equimax (ivermectin and praziquantel) March and September - use next wormer after 6 weeks

Panacur Guard (fenbendazole) use in November and/or February - next dose after 6 weeks.

Pyratape (pyrantel) 4 - 6 weeks

Worming is now a complicated subject and if you require any further information or worming charts, please contact the surgery.