Prescription-only anthelmintics–a questionnaire survey of strategies for surveillance and control of equine strongyles in Denmark.

The research article surveys strategies used for the surveillance and control of equine strongyles in Danish veterinary practices, following the 1999 legislation in Denmark that restricted anthelmintic drugs to prescription-only. The findings suggest that heightened surveillance of strongyles has occurred, but routine screening for anthelmintics resistance remains uncommon.

Background and Method

• The authors initiated this research following the legislation in Denmark in 1999 that limited the distribution of anthelmintic drugs to prescription-only and prevented their use for regular, preventive treatment.
• To understand how this legislation affected strategies for monitoring and controlling equine strongyles, the researchers conducted a questionnaire survey in 2004 in Danish veterinary practices.
• 170 registered equine veterinary practices took part in the survey, with a response rate of 51.2% (87 practices).

Findings

• Most participants (97%) used faecal egg counts for diagnosis and surveillance, and a significant proportion (41%) utilized larval cultures.
• The use of larval cultures was directly associated with the number of employees in the practice and the percentage of equine caseload in the practice.
• Treatment was most commonly performed during spring, summer, and early autumn, aligned with faecal egg count procedures.
• Practices decided on treatment based on various cut-off values ranging from 20 to 500 eggs per gram (EPG) of faeces.
• Important factors involved in the strategies for faecal sampling included ages of horses, clinical suspicions of parasitic disease, and client requests. Other less common strategies included random sampling and sampling all horses on the premises.
• Most respondents (95%) reported sometimes treating certain groups of horses without prior faecal examination, for example horses with clinical signs of parasitic disease (77% of respondents), foals (84%), horses less than 3 years old (52%), and pregnant mares (51%).

Interpretations and Implications

• The respondents identified the cyathostomin group as the prevalent cause of parasitic infections, followed by large strongyles and Parascaris equorum.
• About 67% of the practices routinely alternated between drugs, while only 11% performed regular screening for anthelmintic resistance.
• Results from the survey suggest that equine anthelmintic restriction to prescription-only availability has led to an increase in the surveillance level of strongyles.
• Despite an apparent reduction in treatment intensity, the routine screening for anthelmintic resistance remains uncommon.