The following information can be found on the American Association of Equine Practitioner’s website
Internal parasites, or worms, are silent thieves and killers. They can cause extensive internal damage without you even realizing your animals are heavily infected. The effects of internal parasites on a horse range from a dull haircoat and unthriftiness to colic and death. Internal parasites lower the horse’s resistance to infection, rob the horse of valuable nutrients, and in some cases cause permanent damage to the internal organs.
TYPES OF INTERNAL PARASITES
There are more than 150 species of internal parasites that can infect horses. The most common and troublesome are the following:
- Large strongyles (bloodworms or redworms)
- Small strongyles
- Roundworms (ascarids)
Probably the most important, in terms of health risk, are the first four: large and small strongyles, roundworms and tapeworms.
The lifecycle of most internal parasites involves eggs, larvae (immature worms), and adults (mature worms). Eggs or larvae are deposited onto the ground in the manure of an infected horse. They are swallowed while the horse is grazing, and the larvae mature into adults within the horse’s digestive tract (stomach or intestines). With some species of parasite, the larvae migrate out of the intestine, into other tissues or organs, before returning to the intestine and maturing into egg-laying adults.
DESIGNING A DEWORMING PROGRAM
There are two basic types of deworming programs:
- Continuous— feeding a daily dewormer year-round or throughout the grazing season
- Strategic— deworming only at certain times of the year or when fecal egg counts rise
Combination programs can also be used. For example, continuous deworming can be supplemented with strategic deworming for bots.
There is no single deworming program that suits all horses and all situations. The ideal program for your horse(s) depends on the type, number and ages of the horses on your farm, pasture management and your geographic location. It is best to have your regular veterinarian help you devise an appropriate deworming program for your horse or farm.
Having your veterinarian perform fecal egg counts to determine the amount of egg shedding that your horse has is important. This information will help ensure that the dewormers that are being used are effective and also help determine the frequency of deworming necessary to keep your horse healthy. The outlay of time and money will be well worth it.