Guest blog Janneke van der Wal (Worm& Co): To deworm preventively in winter or not?

Janneke van der Wal from Worm&Co advocates for customized worm management for each horse. Many people give a heavier deworming treatment with Moxidectine at the beginning of winter each year – against redworms, tapeworms, and bots among others. We asked Janneke if this is actually necessary and how you can know.

"Routine deworming every few months throughout the year is really unnecessary," Janneke explains. "About 74% of horses in the Netherlands are dewormed unnecessarily. And every unnecessary deworming treatment leads to resistance in worms." That's why Worm&Co uses fecal egg counts and a detailed questionnaire, so that each individual horse can be dewormed accordingly. Only deworm when it is truly necessary. Janneke says, "Every horse carries gastrointestinal worms. That's okay. Different parasites in the horse's body help it build resistance." A dip in immunity due to factors like moving or stress can cause the worm population to grow, leading to a worm infection that requires treatment, she adds.

Resistance to worms

"The last fecal egg count of the year is between mid-October and mid-November. Fecal egg counts are customized. Our clients always fill out a detailed questionnaire, which helps us determine what the horse needs. For example, we want to know when the horse was last dewormed, with what product, whether it is in contact with young horses, and if manure is removed from the paddock or pasture. We always consider the age of the horse, its living environment, its history, and previous recommendations. All of this leads to the end-of-year advice. If we find an infection in a horse that is not completely fit or has a certain condition, we will not quickly recommend a broad-spectrum deworming treatment. If we find an infection in such a less fit horse, then we will, in consultation with the owner, determine what is best for the horse and create a customized plan. If necessary, you can give another broad-spectrum treatment in early spring, but maybe by then, the horse has resolved the infection on its own. You can see that through fecal egg counts and customized care."

End-of-year treatment for tapeworms and bots?

Worm&Co also bases its end-of-year treatment on research and documentation. Janneke says, "A heavy treatment is not necessary for every horse. For those who prefer not to deworm preventively at all, there is now a saliva test available for tapeworms. This is because tapeworms are not optimally detectable through fecal egg counts. Most horses do not carry tapeworms, although we have seen a slightly increase in tapeworm infections in the Netherlands in recent years. This is partly due to horses being outdoors year-round more often, increasing the chance of reinfection. But if the horse tests negative on the tapeworm saliva test, it may indicate that the heavy treatment is not necessary." The end-of-year treatment is also often given for bots, which can enter a horse through their coat via eggs and are not detectable through fecal egg counts. Janneke says, "First and foremost, horses can indeed get sick from bots. But do not let fear dictate your actions. The majority of horses can handle a bot infestation on their own. We see more horse owners choosing not to deworm preventively against bot larvae. Many owners also remove the eggs, although that is not a guarantee. You can always overlook some eggs, and if horses snuggle together, there can also be transmission. A broad-spectrum treatment works against bots, but lighter worm treatments with ivermectin work as well."

Customization

What do we do with a fit horse that has not been dewormed for a long time? Should we still give a standard end-of-year treatment? Janneke says, "You really have to consider everything before deciding if an end-of-year treatment is necessary. That does not mean giving such a heavy treatment as standard, but assessing the situation each year, customized for each horse. That is really important." She also recommends giving the end-of-year treatment typically in December or January. "In autumn, it is often still warm with fluctuating temperatures. If horses test positive in October, then we assess if the broad-spectrum is necessary. If so, you wouldn't deworm again at the end of the year. Otherwise, it's better to wait until it is truly winter. At Worm&Co, you always receive a fitting advice and reminder of the best time to administer the end-of-year treatment. Worm management is and remains tailored. No one wants to give their horse unnecessary medication," Janneke concludes.

www.wormenco.nl