Horses: When to FEC | FEC for horses

What to do when?

Because different worms have different life cycles and susceptibility to different wormer types it is important for us to get the most out of wormers to be using the correct wormer at the correct time of year. It is also extremely important to ensure that when you do need to worm that you use correct dosage rates for the weight of your animal. Visual estimation of weight often results in under dosing and this is then a major contributing factor to developing wormer resistance. It is therefore recommended that weight tapes are used to improve accuracy.

When should I worm for roundworms?

During the grazing season when you are most likely to be doing a worm egg count we generally suggest (assuming people are content with their provision for tapeworm treatment) in line with current thinking that horses with a worm egg count greater than 200 epg are treated with either:

Ivermectin : (ie Eqvalan, Noromectin, Maximec, Eraquell, Annimec, Vectin, Furexel) Followed by a repeat worm egg count 10 weeks after treatment

or Pyrantel (normal dose): (ie Exodus, Strongid P, Pyratape, Provid, Embotape) Followed by a repeat worm egg count 8 weeks after treatment

If you are concerned regarding tapeworm during the grazing then you can use a combination wormer containing Ivermectin and Praziqunatel (Equimax, Eqvalan duo, Furexel Combi)

or a double dose of a Pyrantel wormer.

We believe the only consistent currently licensed treatment for encysted cyathastomins is using a moxidectin based product (Equest or Equest Pramox). On the whole at the end of the grazing season most of the larvae become encysted. The danger period is when these encysted larvae emerge again in the spring. Given the clinical seriousness of a mass emergence of encysted cyathastomins which can result in diarrhoea, weight loss and colic, coupled with the current inability to accurately determine encysted larvae numbers has meant that we generally advise a minimum of once yearly treatment with a moxidectin based product between late October and early December

When should I worm for tapeworm?

Care should be taken to consider treatments or testing for tapeworm. To detect the tapeworm burden an ELISA blood sample can be useful. There is some debate as to how often you should worm you horse for tapeworm and this probably relates to a number of risk factors. In low risk horses once a year worming for tapeworm is likely to be effective. We generally recommend this is done in combination with the encysyted cyathastomin dose (Equest Pramox) in late autumn/early winter. For higher risk horses a subsequent dose in the spring is warranted. Products containing praziquantel or a double dose of Pyrantel should be sufficient to be effective against tapeworm.

But what about Bots?

Bot fly larvae while not technically worms can infect horses although rarely cause clinical problems. They are sensitive to the macrocyclic lactones (Ivermectin and Moxidectin) and usually a once a year treatment in early winter when the bot flies have gone is sufficient for good control. Given the above we are therefore currently suggesting treating horses with an epg result greater than 200 with Ivermectin and then with a minimum of one Pramox in approximately November. See below for an example of how this might work within a calendar of strategic worming.