Deworming Equines: It’s Time for Selective Use

A national survey conducted by ANSES provides the most comprehensive overview to date of internal parasite control practices among equines in France. Of the 42,528 questionnaires sent out, 4,344 usable responses were collected, covering 93% of French departments. The results confirm a disconnect between actual practices in the field and recommendations aimed at limiting resistance to anthelmintics (systematic use of deworming, low adoption of selective treatments, often approximate dosing, poor pasture management, etc.).  

A quantitative overview covering the entire country

Mapping the responses reveals an overrepresentation of the Northwest (26.1% of responses), with higher concentrations of participation in Calvados and Loire-Atlantique. About seven out of ten respondents are not professionals, which reflects the reality of parasitic management in recreational facilities and small stables.  

Frequent administration of anthelmintics, even when the risk is low

Depending on the horses’ age, 65.3% to 90.4% of owners report treating their horses systematically, even in the absence of a major risk of infestation. The use of a single class of anthelmintics predominates: ivermectin is used by 73.7% of respondents for foals and by 92.1% for horses over 1 year old, a practice that promotes the selection of resistant parasites.  

Adoption of selective treatments remains limited

Despite European and North American recommendations, the approach based on parasitology diagnostic tests (fecal examination, fecal shedding thresholds, targeted parasites) remains the exception. Only 5.2% of respondents reported performing fecal examinations and administering selective treatment to horses over 1 year of age. Relative to the sample, this represents approximately 226 owners out of 4,344. In other words, nearly 19 out of 20 continue to perform anthelmintic treatment blindly, without quantifying egg shedding or evaluating post-treatment efficacy.  

Approximate Dosages

Approximately 70% of respondents estimate their horse’s weight visually or administer a standard dose identical to all horses (3,041 responses out of 4,344). This practice leads either to underdosing—a recognized risk factor in anthelmintic resistance—or to an unnecessary overdose, resulting in additional costs and iatrogenic risks.  

Inadequate pasture management

In terms of environmental prevention, while pasture rotation is widely practiced (about 80% of respondents use it), only 27% of them collect manure several times a year. Mixed grazing with ruminants—a practice that is beneficial for limiting the level of strongyle larvae infestation in pastures—is cited by only 18% of respondents.  

Treatment that is not very targeted or systematic

The frequency of deworming is higher among professional breeders than among private owners, among foals than among adults, and among racehorses than among other breed groups. These differences in strategy reflect competitive pressures and specific risk factors, but they also highlight that health management is not based on the results of fecal examinations or on monitoring post-treatment efficacy through tests to measure the reduction in fecal egg shedding.  

The Key Role of the Veterinarian

In addition to veterinary anthelmintic protocols, 20.6% of respondents (895 owners) reported using alternative or complementary products, often purchased online. This variety of methods complicates traceability and the evaluation of results, especially in the absence of follow-up fecal examinations. However, despite these differing practices, the veterinarian remains the primary source of advice for establishing a deworming plan. This key role helps drive the shift toward proven strategies (regular fecal examinations, selective treatment of high-shedding horses, dosing based on actual weight, efficacy checks, and treatment intervals).  

Data Supporting a Change in Strategy

Taken together, these results point to an approach with diminishing effectiveness (untargeted anthelmintic treatment, use of a single active ingredient, imprecise dosing, and irregular pasture management). However, the equine therapeutic arsenal remains limited to four classes of anthelmintics; reducing their effectiveness through non-selective practices amounts to jeopardizing parasitic control in the medium term, leading to clinical failures, increased costs, and a risk of disease in the most susceptible horses.  

What the literature recommends

The successful strategy rests on four pillars. First, assess the parasitic risk before treating (fecal examinations, diagnostic tests). Next, administer the correct dose based on the horse’s actual weight, not an estimate. Third, manage pastures (rotation, regular removal of manure, sensible mixed grazing, harrowing). Finally, establish an individualized deworming plan (protocol selected by the veterinarian, traceability of treatments, and discontinuation of alternative practices).   This survey provides a statistical basis for reorganizing the fight against intestinal parasites in horses in France. The figures speak for themselves: Only 226 horse owners report using targeted treatment; 3,041 still approximate the dose of anthelmintic medication administered; 3,500 practice pasture rotation, but only 1,180 regularly remove manure. Adopting a rational and selective anthelmintic plan is not an option—it is essential to preserving the effectiveness of antiparasitic drugs, the health of horses, and the economic stability of stables.