Worms | Horse Racing Free Tips

Double Down: Traditional Deworming Increases Drug Resistance At Alarming Rate

Traditional deworming methods dictate that all horses on a farm be dewormed with moxidectin or ivermectin at specific intervals, usually every other month or quarterly. Though significantly easier on farm managers, this method increases anthelmintic resistance two to three times more rapidly than other deworming programs, reports The Horse.

Dr. Thomas Geruden, with Zoetis in Belgium, said these results are not surprising as the worm population is continuously pressured for selection of survivable genes in the calendar-based deworming routine.

Geurden and other researchers in Belgium, along with scientists at the Gluck Equine Research Center in Lexington, Ky., studied two farms that utilized the standard deworming protocol on their Belgian draft horses.

The deworming schedule should have corresponded with the timeline of worm egg development, but drug resistance has caused the worm eggs to appear twice as fast as expected.

Fecal egg counts on every horse on the farm were performed every two weeks from April to September for three years. Horses that had more than 250 eggs per gram of manure were given pyrantel embonate, an alternative dewormer. All other horses were treated with standard anthelmintics in the spring and fall, reducing their deworming by half or two-thirds.

The researchers used the fecal egg counts, both before and after treatment, to create a model of worm life cycles that could predict drug resistance over the next 40 years. The team found that the alternative dewormer maintained low egg counts in all horses and slowed drug resistance in worms by 200 to 300 percent.

The scientists also found that the horses considered “high shedders” of worms were almost always under 5 years old. This knowledge might allow horse owners and caretakers to target which horses may need fecal egg counts run more often – and which may need more-frequent treatments.

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The data suggests that fecal samples should be gathered for egg counts between 42 and 56 days after the spring moxidectin/ivermectin treatment, with a second sample taken between days 98 and 112. These numbers will help determine future egg counts and reduce deworming frequency.

The ability to model the rate of anthelmintic resistance using different deworming protocols has been helpful when discussing deworming with both horse owners and vets, the researchers found. A deworming plan specifically tailored to a farm may be more expensive initially, but the less-frequent, targeted deworming will pay off financially in the long run as dewormer resistance slows.

Is Your Steed Sleepy? Anemia May Be To Blame

Anemia in humans often manifests as tiredness or weakness. The condition is caused by a lack of enough healthy red blood cells to carry enough oxygen to their tissues, and often leads to compromised metabolic and immune system functions. Though the causes can vary, some types of anemia can be prevented by eating a healthy, varied diet that includes a plethora of vitamins and minerals.

Iron-deficiency anemia in horses is rare, but it does happen. Most horses get sufficient amounts of iron in their diet from hay, pasture, and commercial feeds. An average horse needs 400 to 500 mg of iron per 500 kg of body weight, reports Dr. Gulsah Kaya Karasu of AGG Equine Nutrition Consulting in EQUUS magazine.

Horses may end up with anemia because of blood loss (causes may include an injury, cancer, or ulcers), reduced blood cell production, or blood cell destruction.

Some infections, like equine infectious anemia, can lead to red blood cell destruction, as can a heavy worm burden, particularly large strongyles. Chronic kidney disease, cancer, and a few other disorders can prevent a horse from making adequate red blood cells.

An anemic horse will have pale mucous membranes and an increased heart rate, in addition to being sluggish. Adding additional iron to the affected horse's diet isn't recommended as excessive iron can lead to depression, diarrhea, and compromised immune function. It can also interfere with the body's ability to absorb other minerals and increase the risk of a horse becoming insulin resistant.

Iron-related anemia is rare in horses, so a thorough investigation by a vet is recommended for diagnosis.

Study: Flaxseed Oil Can Reduce Strongyle Load In Horses

Vegetable oils are often added to equine diets to supplement fat and energy, but adding flaxseed oil (also called linseed oil) now has an additional equine health benefit: it can significantly reduce strongyle load in horses. This finding is especially important as strongyles have become more resistant to available deworming medications.

A Polish study added pure flaxseed oil to the diet of 15 Thoroughbred and 12 Arabian horses that were fed oats, muesli, and hay three times a day. The horses were separated into four groups fed soybean oil, flaxseed oil, flaxseed oil and vitamin E, and one group with no added oil that served as a control. Lead researcher Dr. Wanda Górniak had the horses dewormed with ivermectin and praziquantel in February 2020.

In June 2020, researchers performed fecal egg counts on samples from the horses. The researchers found that 25 of the 27 horses had worms, with strongyles the most prevalent; one-third of the horses also had threadworms. The horses that had been fed flaxseed oil have the lowest prevalence of strongyles (71 percent compared to 100 percent in other groups).

The scientists concluded that the adding flaxseed oil to a horse's diet significantly reduces its strongyle worm load.

Read the study here.

Could Fruit Provide The Answer To Growing Dewormer Resistance?

Dewormer resistance is a critical concern for horse owners all over the world. With no new deworming products in the works, scientists are beginning to research more natural means of controlling the internal parasites.

A preliminary study from England suggests that an enzyme found in fruits like papaya, pineapple and figs can prevent parasite eggs from hatching in a laboratory setting. A previous study found that cysteine proteinases can kill adult worms so Dr. Laura Peachey and her team tested the theory that these enzymes may also inhibit parasite eggs from hatching.

Peachey's results confirmed these enzymes could inhibit hatching and also found that the enzymes inhibited the movement of small red worms in their infective stage. The researchers are unsure if the limited mobility is related to the cysteine proteinases or another compound in the extract. More research is needed to see how the enzymes do their work.