In the United States, equine dewormer medication is available over-the-counter for horse owners to buy and administer without input from a veterinary practitioner. Several EU countries, namely Austria, Germany and Denmark, have prescription-only restrictions that promote the use of fecal egg counts (FEC) coupled with equine veterinarian involvement in deworming strategies. The Netherlands implemented these restrictions in 2008, whereas Austria and Germany have had them in place for decades.
A recent survey of owners of 3,092 horses helped to evaluate the usage of FEC and anthelmintic treatment across three different age groups—foals; 1-3 year olds; and greater than 3 years old—in Austria, Germany, Denmark, the Netherlands and the USA [A.M. Bechera; D.C. van Doorn; K. Pfister; R.M. Kaplan; M. Reist; M.K. Nielsen. Equine parasite control and the role of national legislation – A multinational questionnaire survey. Veterinary Parasitology 259 (2018) 6–12].
The use of FECs enables selective (targeted) deworming methods to reduce the intensity of anthelmintic treatment. This strategy is an attempt to slow and diminish parasite resistance to dewormers. The study findings indicate that Denmark horse owners use a significantly different strategy than the other four countries. This is despite the fact that Denmark implemented prescription restrictions in 1999 compared to Austria and Germany with a history of 30-40 years of prescription requirements for deworming based on diagnostic testing. Denmark respondents use more fecal analyses and treat less often. Denmark requires individual testing; Germany allows herd-based strategies for fecal testing and treatment.
Interestingly, there were little differences between strategies used by Austria, Germany, the Netherlands and the USA despite the fact that only the USA has OTC availability of anthelmintics. Other pertinent findings from the survey indicate that while 50% of US respondents have fecal egg count testing done at least once a year, only 10% use this information to guide treatment strategies. Furthermore, 70% of USA respondents treat adult horses four or more times per year, not too dissimilar to frequency of anthelmintic treatment in the 1990s.
It appears that the understanding about selective deworming based on FECs is not well understood by American horse owners.
About 60% of the Netherlands respondents treat four or more times per year; few German respondents base treatment decisions on FECs and they also use benzimidazoles despite known parasite resistance.
In contrast, 45% of Danish respondents treat adult horses two or fewer times per year, while the other half treat based on fecal egg counts. The Danish strategy is markedly different from the other four countries.
The authors additionally stated, “A recent British study investigating factors affecting the use of FEC-based equine parasite control programs concluded that emphasizing the dangers of parasite infection and anthelmintic resistance had limited influence on the parasite control approach chosen (Vineer et al., 2017). Instead, the authors found that general knowledge about parasite biology, control options, and practical implementation of FECs made respondents more likely to adopt these recommendations.”
In summary, it appears that continuing educational efforts are important to provide horse-owning clients with the motivation to deworm based on scientific surveillance strategies rather than the traditional, decades-old method of deworming every two months. With no new anthelmintic treatments in development, it is essential to inspire horse owners to maximize efficacy of the deworming medications currently available.