Equine Parasites
Internal parasites are silent killers. They can cause extensive internal damage, and you may not even realize your animals are heavily infected. At the very least, parasites can lower resistance, rob the horse of valuable nutrients, and cause gastrointestinal irritation and unthriftiness. At their worst, they can lead to colic, intestinal ruptures, and death. There are more than 150 internal parasites that afflict horses, including several major species. Among the most common and troublesome are: large strongyles (bloodworms), small strongyles, ascarids (roundworms), pinworms, bots, tapeworms, threadworms and lungworms . Any or all of these parasites can be present in the horse at one time, but they may be at different stages in their life cycles. This will influence the deworming program needed to combat them. Also, keep in mind that some species can lay more than 200,000 eggs a day, so parasite loads can escalate quickly.
Different parasites harm the horse in different ways. They can damage tissues and vital organs, including the major blood vessels to the intestines, lungs, liver, stomach, and intestines, as they migrate through the horse’s system to complete their life cycles. They can cause obstructions and ulcerations within the horse’s digestive tract, and they can also cause intense irritation as they lay eggs, such as pinworms do.
Contrary to popular belief, many horses that have dangerous parasite levels appear to be perfectly healthy. From the outside they may be fat, sleek and shiny, while on the inside the worms are doing irreparable damage. But in other horses, especially young horses, parasites can take a visible toll. Signs of infestation might include: dull, rough haircoat, lethargy
or decreased stamina, weight loss, coughing and/or nasal discharge, tail rubbing and hair loss, colic, depression, loss of appetite, unthriftiness or loss of condition and diarrhea.
One of the most under-utilized tools in an effective parasite control program is the fecal examination, which merely involves taking two to three fresh fecal balls to your veterinarian for laboratory analysis. This simple process can identify the specific parasites infecting a horse. Rarely are the worms themselves visible in the manure. But by counting the types and numbers of parasite eggs present in the fecal sample, your veterinarian can recommend the right deworming agents to do the job. Fecal eggs per gram counts (EPG) also tell an owner about the degree of parasite infestation on a farm or within a herd. The fecal exam is a cost-effective follow-up to deworming to determine whether the dewormer has worked. It’s good practice to do a fecal EPG count within two weeks after deworming.
Parasites can develop resistance to many of the chemicals used to kill them. After a period, the deworming agents may therefore simply become ineffective. To prevent this, it’s important to rotate classes of drugs used in your program. Be sure that you don’t simply change brand names, however, since many products contain the same drugs but under different labels. Although some manufacturers claim that certain products do not require rotation, a good safeguard is to do it anyway. That way, there’s no question about resistance developing. With opinions varying as to how often dewormers should be rotated, Dr. Doornekamp can put a deworming package together for you that contains a years worth of deworming agents based on your horse’s needs. Please contact the office for more information.
By utilizing broad-spectrum deworming agents and rotating them as recommended by your veterinarian, you should be able to rid your horse of most worms.
Please note: advice given as a guide only and specific advice may vary for individual horses. OES does not accept responsibility for any problems resulting from inappropriate interpretation of advice. If you have any doubt about your horse's health, always consult a vet.