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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.

Veterinarians: Dewormer Resistance Must Be Addressed To Avert Equine Welfare Disaster

Though veterinarians and equine caretakers around the world have stressed the importance of forgoing the once-standard practice of rotational deworming, a recent study shows that dewormer resistance is still looming. Currently, small redworms and large roundworms are resistant to all available dewormers; no new dewormers are currently in creation.

Members of the British Equine Veterinary Association (BEVA) anthelmintic working group wrote to the Veterinary Record to express their concern over the findings of a small-scale study. Dr. David Rendle and his colleagues state that a “anthelmintic resistance disaster” is looming unless horse owners change horse-keeping ways.

The study found that although there has been an uptick in the number of fecal worm egg counts (FWECs) performed, there has not been a corresponding downward trend in dewormer sales. The BEVA working group gathered information on the number of fecal worm egg counts completed and the sale of dewormers in the U.K. from 2015 to 2018.

Though FWECs increased by 29 percent, the doses of dewormer sold only fell by 2.9 percent over the same period. The sale of these drugs dropped 8 percent between 2015 and 2016, and then rose every year after that.

If the deworming guidelines were being followed correctly, and dewormers would only be given when a FWEC deemed them necessary. There should be at least twice as many FWECs completed as doses of dewormer sold. However, the data shows that there was only one FWEC completed for every 11 doses of dewormer sold.

The authors also point out that moxidectin sales remained high throughout the study period though experts have noted that it should not be used as a routine dewormer in horses.

Small Strongyles Showing Resistance To Last Effective Class Of Dewormer

Martin Nielsen, DVM, Ph.D., Dipl. ACVM, Schlaikjer professor of equine infectious diseases in the Gluck Equine Research Center, presented his research on small strongyles at the University of Kentucky's Equine Research Showcase in February.

He spoke about current data showing resistance among cyathostomins (small strongyles) to the three main groups of anthelmintic (anti-parasitic) drugs.

“The small strongyle parasite, which is the type of parasite that all horses get, is the primary parasite category, the one that we are always deworming for,” Nielsen said.

The first class of anthelmintic drugs introduced and administered to combat small strongyles was the benzimidazoles in the 1960s. Because this class of drugs has been in use the longest, there is wide-spread resistanceto these drugs.

“It is very rare to find these products still working,” Nielsen said.

Pyrantel salts began experiencing resistance in 1996 and Nielsen said it is also likely to find small strongyles resistant to Pyrantel dewormers today.

Macrocyclic lactones (ivermectin and moxidectin) are our “last resort,” with good efficacy, but there have been some questionable early signs of emerging resistance reported, according to Nielsen. In 2020, routine data collected from a farm in Central Kentucky confirmed resistance to macrocyclic lactones among small strongyles.

Nielsen shared data showing that macrocyclic lactones were 100 percent effective against small strongyles in a group of U.S.-bred yearlings, but the same dewormers administered to a group of imported, Irish-bred yearlings failed to remove small strongyle parasites.

“There's no doubt, looking across this data, that we have clear-cut, proven resistance to ivermectin in these imported parasites,” Nielsen said. “The problem is, if we have resistance to everything, what can we deworm with?” he said.

He described that the efficacy of moxidectin was also evaluated against the resistant parasites. Despite this drug being potentially more potent than ivermectin, it did not overcome the resistance and did not provide better efficacy.

Nielsen closed with a final note that ivermectin and moxidectin resistance is occurring in small strongyles. This case was only discovered due to the meticulous testing procedures in place on this particular farm. Without regular testing of deworming efficacy, drug resistant parasites will go undetected and farms will be left without opportunities to intervene before it is too late. Good parasite control starts and ends with testing the dewormers being used and this must be done every year.