This month’s topic is horse parasite control, specifically what products D&B Supply carries and how they work. Currently your choices include: Quest (moxidectan), Equimax (Ivermectin/Praziquantel), Rotectin P (Pyrantel), Ivercare(Ivermectin), Safeguard (Fenbendazole), Stonglycare (Pyrantel), Iverease (Ivermectin), and Horse Health (Ivermectin). As you can see there are basically four main active ingredients with praziquantel thrown in for tapeworm control: moxidectan, ivermectin, pyrantel and fenbendazole.
Ivermectin is one of the most effective dewormers available on the market because of its broad spectrum of activity. This product is effective against large strongyles, small strongyles, stomach worms, pinworms, ascarids, threadworms, and bots. There have been some reports of parasite resistance to this drug but it is rare.
Moxidectin is one of the newest dewormers and was developed in 1997. It’s spectrum of activity is similar to ivermectin except that it is more effective against some of the larval stages of small strongyles.
Fenbendazole is effective against large strongyles, small strongyles, pinworms and ascarids. To be most effective it is usually given for five consecutive days. This product is extremely safe and can be used in pregnant mares and young foals.
Pyrantel is the oldest deworming product of the four and is effective against large and small strongyles, pinworms and ascarids. This product is sometimes used as a daily treatment in the feed (Strongid-C).
Praziquantel (as sold mixed with ivermectin in Equimax) is effective against tapeworms.
A deworming program should ideally be tailored to the individual horse or heard. When the products should be used and which product to use depends on the type of parasites the animal will encounter. A definitive diagnosis can be made by examining fecal samples for parasite eggs. This is the only way to accurately determine which products should be used and when. Once you determine what parasites you are dealing with you can then make some intelligent decisions about product selection. In general, foals should be more intensively dewormed due to ascarid infestations that can be very serious. Some foals may need to be dewormed monthly during their first year of life. Again, this should be based on fecal exams. Adults should be dewormed in the spring and the fall with a product containing ivermectin or moxidectin. This should be a minimum. The decision to add additional treatments should be based on fecal exams. “Rotational deworming” (i.e. using different products at diffent times) is an idea that was developed to reduce the likelihood of developing parasites that are resistant to some of the broad spectrum products such as ivermectin. While resistance has been documented, it is a rare occurance and not a good reason not to use the more powerful products at critical times. If your fecal exams reveal low egg counts during the summer of parasites susceptible to products such as pyrantel then this might make sense. Again, the decision should be based upon objective data and not just a habit or a form that the drug manufacturer prints out. Ideally you should perform fecal exams 2 weeks after deworming to asses the effectiveness of the treatment.
Deworming products are only a part of the parasite control program. Pasture rotation, mucking out stalls to remove fecal material, removal of bot eggs, and not feeding off of the ground are all management practices that can be used to reduce parasites in horses.