Keeping a Backyard Horse

Parasite Control

Another often-neglected aspect of caring for a horse is parasite control. From the time we are very young, horses will have a variety of parasites (worms) in our bodies. Having a little knowledge of the life cycle of parasites can help you develop a deworming schedule suitable to your horse and your climate.

In the case of bot flies, (the one parasite you're likely to actually SEE on your horse), the adult fly lays eggs on the horse's fur. You may notice these eggs appear as tiny yellow spots on the horse's front legs, back legs, chest, and belly area. The eggs will itch, and so we tend to rub or bite at them. The warmth of our mouths causes the eggs to hatch, and the larvae then enter the mouth and our gastrointestinal system. The larvae begin to mature in our system, so that by the time they emerge in our manure, they are nearly adult flies.

Other parasites operate in much the same way. They are picked up off the ground as we eat, and travel through our bodies as they mature. A low level of parasitism won't bother a healthy horse, but a heavy load will begin to sap nutrients from the body. You will never completely rid us of these parasites. If your horse experiences a sudden weight loss, in the absence of signs of illness (fever, depression, not eating, etc.), suspect parasites.

The first weapon in your arsenal against parasites should be good housekeeping (or horsekeeping!). Daily removal of manure from your stall or pen will greatly reduce the amount of worm larvae that your horse may pick up while eating. Even if you don't have a place to dispose of manure, simply moving it to a pile in one corner of the pen will help. Horse manure is very hot, and when piled up, will eventually burn itself down.

You won't be able to remove all traces of manure from your pen, but raking it up and breaking what's left into smaller pieces, and spreading it out will allow the sun to assist your parasite control program by killing any larvae that may be left behind. And by removing manure as far away as possible, you can help to keep down the smell of your pen, as well as attracting the flies away. Mom uses a springy grass rake and a sturdy snow shovel (flat-ended) to remove manure, and it seems to work well for her. A wheel barrow or wagon is also useful, or a trailer that pulls behind a riding lawn mower.

Mom spends a lot of time cleaning manure. She always makes sure my stall is clean and dry, and sometimes she removes manure from other areas too. But I've learned and I try to go where the manure already is. When I'm feeling playful, I'll follow her around, or even knock over the wheelbarrow! Whenever I do that, she just laughs, calls me silly, stands up the wheelbarrow, and cleans up the pile again. I remember one time when I actually pooped into the wheelbarrow while she was working! She laughed so hard and hugged me tight. I love to hear her laugh. Sometimes, when she was working and didn't have time, or when she got really sick, my dad or my sisters would clean my pen and stall.

Another way to fight parasitism is through the use of anthelmintic drugs, commonly known as dewormers. These medications are available in different classes, as well as in many different forms and even flavors. The most commonly used is probably 1.87% ivermectin (some brand names Zimecterin® by Merial or Ivercare® by Farnam). This medication is effective against many forms of parasites, including the bot fly, and is safe to use in horses of all ages, including pregnant mares. It comes in the form of a paste in a tube with a handle that you can dial in to your horse's estimated weight (a height/weight tape is useful for this) for the proper dosage. You simply remove the cap and squirt the paste into the back of your horse's mouth. Keep in mind, he will probably try to spit it out. For a full grown horse, even if the weight is slightly less than the full 1,200 pound dosage, you can deliver the full dose without worrying about an overdose.

Another common medication is called 43.9% pyrantel. It's a different class of drug than ivermectin, and is available in paste, liquid, or even pellets (as a daily dewormer). It is important to note that pyrantel is not effective against the bot flies, so don't choose this medication if you see the fly eggs on your horse's fur. The liquid form and pellets can be mixed in with your horse's feed. Follow dosing instructions on the package.

Two other types of dewormers are 10% fenbendazole (Safeguard®) and 2% moxidectin (Quest®), available in paste and gel forms. These different classes of drugs can be useful in a rotating deworming schedule, so that the parasites who may survive one treatment don't become resistant to one particular drug.

Talk to your veterinarian about a deworming schedule and rotation suitable for your horse and your location. Generally speaking, you should deworm your horse every eight weeks in most climates. If your winters get extremely cold, you might be able to stretch that to 10 weeks, or skip the mid-winter deworming altogether. As to your rotation, it's up to you and your vet to decide what to use.

My mom usually gives me deworming medicine regularly every eight weeks (except for when she tried to get me pregnant, because deworming isn't recommended in the first two months of pregnancy). She will give me ivermectin twice, and on the third treatment switch to pyrantel, then go back to ivermectin for two treatments. This schedule and rotation, as well as the daily removal of manure, serves to keep me as worm-free as possible, here in southeast Missouri. Again, talk to your vet about a proper schedule for your horse.

In certain areas of the country, you'll also have to be on the lookout for ticks and fleas. Deer ticks will also bite horses, and can be responsible for the spreading of West Nile disease. There are products available to put down your horse's back, similar to those you might use on your dog or cat. Ticks love tall grasses, so keeping the area around the outside of your pen mowed short can help reduce their numbers. Also, keep in mind they might come inside your hay bales, especially large ones, so keep an eye on your horse's face to find and remove ticks.