Helminth infections remain highly prevalent among grazing equids worldwide, with cyathostomins and the tapeworm Anoplocephala perfoliata representing the most widespread parasites. While most horses tolerate low helminth burdens without overt clinical signs, a minority develop higher burdens that can result in substantial intestinal pathology. Infection with A. perfoliata burdens exceeding 20 worms has been strongly associated with mucosal ulceration, ileocaecal valve dysfunction and various forms of colic. Consequently, mounting evidence of reduced anthelmintic efficacy against A. perfoliata represents a growing concern, particularly in light of the apparent absence of a drug development pipeline for equine anthelmintics. This situation highlights the need for sustainable, evidence-based control strategies that favour diagnostic-led treatments over routine blanket deworming. Traditional coprological methods, although integral to nematode control, lack sensitivity for detecting A. perfoliata due to the parasite’s intermittent egg shedding and typically low faecal egg output. In contrast, serological and salivary immunoassays targeting parasite-specific IgG(T) have been developed, providing a more sensitive means of assessing infection status, with antibody levels shown to correlate with tapeworm infection levels. Incorporation of these tests into helminth control programmes enables targeted treatment of infected horses while minimising unnecessary anthelmintic use in individuals with little or no infection. When combined with robust pasture management practices, including regular faecal removal, maintenance of low stocking densities, rotational grazing with non-equine species and adequate paddock rest periods, diagnostic-led approaches can substantially reduce reliance on anthelmintics. This not only helps preserve drug efficacy through the maintenance of refugia but also supports sustainable long-term control of equine tapeworm infections. However, there remains an urgent need to develop validated methods for assessing anthelmintic efficacy against A. perfoliata, which should be a key priority for future research.

Background: A reduction in the Egg Reappearance Period (ERP) has been suggested to be an early indication of emerging anthelmintic resistance in strongyles. Objective:To measure the strongyle ERP following moxidectin treatment of horses in the southeast of England. Study Design: Prospective study. Methods: Horses with a faecal egg count (FEC) of > 400 strongyle eggs per gram (EPG) in a routine screening sample were enrolled into the study. Moxidectin (400 mcg/kg) was administered per os and FEC tests repeated every 2 weeks for 16 weeks. Results: Forty-eight horses completed the study. The mean EPG prior to treatment was 1047 (range 375 – 2137 EPG). In all but two horses, FEC was 0 EPG 2 weeks after moxidectin administration. In the remaining two, the FECs were 12.5 EPG (97.8-98.3% reductions compared to pre-treatment FEC). At 4 weeks post-treatment, 6 horses had positive FECs (96.6-99.2% reductions). At 6 weeks, 11 horses had positive FECs (83.8% reduction in one horse; >90% reduction in 10). At 8 weeks, 21 horses exhibited positive FECs (<90% reduction in 2). At 10 weeks, 27 horses had positive FECs (<90% in 6). At 12 weeks, 31 horses had positive FECs (<90% reduction in 11). At 14 weeks, 34 horses had positive FECs (<90% reduction in 13). At 16 weeks, 38 horses had positive FECs (<90% reduction in 17). Limitations: Weights of some horses were estimated using weigh tapes rather than a weighbridge. Dosing of the horses with moxidectin was carried out by owners. Conclusions: The results indicated acceptable efficacy of moxidectin at 14 days after treatment; however, the ERP pattern measured across the group suggest that this anthelmintic has a considerably shorter suppressive effect on strongyle egg shedding than measured when it was first introduced ( >13 weeks and up to 24 weeks).