Retained efficacy of ivermectin against cyathostomins in Swedish horse establishments practicing selective anthelmintic treatment.

The research article investigates the effectiveness of ivermectin, a commonly used antiparasitic drug, on cyathostomins (a type of horse parasite) in Swedish equine institutions practicing selective antiparasitic treatment. Findings indicate ivermectin still efficiently combats these parasites, supporting the continued use of selective deworming tactics, which may reduce the possibility of antiparasitic drug resistance.

Background and Objectives

• The study aims to evaluate the potency and impact of ivermectin, an anthelmintic drug, on cyathostomins within the horse population in Sweden. These internal parasites are highly prevalent among grazing horses.
• The widespread and uncontrolled use of anthelmintic medications has resulted in the parasites developing resistance to them. This includes macrocyclic lactones (a drug group to which ivermectin belongs), thereby framing the importance of evaluating its effectiveness.
• Specific measurement tools such as the faecal egg count reduction test (FECRT) and the egg reappearance period (ERP) test were utilized to identify antiparasitic resistance and assess the efficiency of the deworming process.

Methodology

• The research was conducted at 16 equestrian establishments that housed at least six horses excreting a minimum of 150 eggs per gram faeces at the screening stage.
• FECRTs and ERPs were ascertained by collecting faecal samples before and two weeks after horses were treated with ivermectin. The collection continued at weekly intervals for eight weeks.
• Additionally, a questionnaire detailing pasture management methods and anthelmintic routines was answered by participants to draw more detailed conclusions.

Results and Discussion

• The survey results pointed out that most establishments (69%) provided anthelmintic drugs to the horses only if faecal diagnostics indicated the necessity.
• All examined establishments had an average FECRT exceeding 99.0% and ERPs varying from six to over eight weeks. This points towards the effectiveness of selective deworming regimens and the efficiency of ivermectin.
• The study also found that the ERP increased with age, with younger horses starting to excrete cyathostomin eggs earlier post-treatment than their older counterparts.
• Establishments like riding schools, stud farms, and those not using distinct summer and winter paddocks confirmed shorter ERPs.

Conclusion

• In conclusion, the study affirms that selective anthelmintic treatment practices, including the use of ivermectin, remain effective and as such should be continued. This might also help in mitigating the risk related to the development of anthelmintic resistance.