For the past year I have been using worm egg counts (faecal egg counts) as part of Trooper's worming programme. The egg counts can be used to monitor the worm activity in your horse and therefore limit the amount of chemicals that need to be used. There some types of worms that worm egg counts do not detect, these are the encysted redworms, tapeworm and bots; it is important that horses are still treated for these.
The results of a worm egg count are often given in eggs per gram (epg) or strongyles per gram. A reading of 200 epg or less is considered a low reading, it is thought that a horse's own immune system can cope with this level of worms on it's own without the need for additional chemical treatments in most cases. For readings over 200epg treatment is usually recommended. The treatment recommended often depends on how high the reading is, if the horse needs treating for other worms, if they are in foal and numerous other factors.
The faecal egg counts can also be used to check if the wormers are working as they should be. Different chemicals are supposed to last in the horses system for different lengths of time. Unfortunately, resistance is starting to develop in a similar way seen with antibiotics. Limiting the use of unnecessary chemicals with egg counts can help to prevent resistance developing.
Trooper has not had much problem with worm activity while I have been carrying out the egg counts. His initial reading was 50epg (a low reading) all subsequent readings have been clear. He was treated over the winter with an Equest Pramox combination treatment and had a tapeworm treatment about 6 months prior to this. There are a large number of horses in Trooper's field and dung is not collected (which can increase the chance of infection), however as the field is large he would not normally have to graze near dung so this would help to prevent him becoming reinfected.
If you have any further questions into worm egg counts, please do ask.