8.4. Alternative remedies An increasing number of so-called organic or herbal dewormers are appearing in tack shops and online, but the efficacy of these products has never been demonstrated in formal, controlled evaluations. Similar products are also sold for ruminants, and several studies in sheep have consistently demonstrated little or no efficacy of these products (Burke et al., 2020). These products exist primarily because they exploit differences in the labeling requirements for drugs vs. non-drug items. Before a drug can earn label claims for activity against parasites, this fact must be proven unequivocally to the Food and Drug Administration by extensive efficacy and safety testing. Once an anthelmintic is approved by the FDA, the claims that can be made in advertising that drug are regulated by the FDA. In contrast, products that are not considered drugs do not require FDA approval for marketing, and therefore have little to no oversight regarding their label claims and the safety and efficacy of their products.
9. Recommendations for Parasite Control Programs
As a general principle, it should not be a goal to eliminate cyathostomin burdens. All grazing horses are expected to harbor these parasites, which are only mildly pathogenic. Instead, recommendations aim to reduce the infection pressure with these parasites by reducing overall herd strongyle egg output, and thus preventing the rare scenario where clinical disease might occur. However, there are other parasites that deserve consideration as well.
Strongyle control programs should be constructed around strongyle transmission seasons, which vary greatly between regions of the U.S. Figure 2 presents data on development of strongyle eggs to infective larvae in six states representing six different climates. Surveillance-based treatments aimed at suppressing strongyle egg output should always be administered during the active transmission season. This is because there is no need to suppress egg output if most of the eggs are destined to die due to intense cold or hot weather conditions.
Recommendations follow a two-tiered principle. Baseline treatments aim at controlling non- cyathostomin parasites, such as large strongyles, ascarids, and tapeworms, whereas the surveillance-based treatments aim at controlling pasture contamination with cyathostomin eggs.
Two-Tiered Parasite Control Principle
Baseline anthelmintic treatments, which should be considered for all horses.
Surveillance-based treatments administered based on fecal egg counts.
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