Shortened egg reappearance after ivermectin or moxidectin use in horses in the UK.

The research article focuses on the study of the reappearance of eggs (ERP) after the use of ivermectin or moxidectin in horses in the UK, specifically those with a persistent positive faecal egg count (FEC), indicating an indication of strongyle infection. The study concluded that the egg reappearance period is shorter than previously believed.

Overview

• The study involves an examination of UK horses deemed at high risk of strongyle infection. The predictors were the usage of either ivermectin or moxidectin and the time period after which faecal egg count returns to positive. Also, the researchers looked at cases where FEC remained positive, even after the normal expected egg reappearance period (ERP) post-treatment.

Selection of Premises and Horses

• The study focused primarily on pleasure horses from the UK believed to be at a significantly high risk of strongyle infection.
• There were different scenarios studied. On 16 premises where moxidectin was used, five recorded an ERP of at least 12 weeks as per two different measuring metrics.
• On the premises where moxidectin was administered to only one animal and evaluated as a group, the ERP recorded was at least 10 weeks.

Ivermectin Use and ERP

• For premises where ivermectin was employed, the ERP was a minimum of 5 weeks.
• In places where only one horse was present or tested, and ivermectin was used, when analyzed as a group, showed an ERP of at least 6 weeks.

Significance of the Research Findings

• The research data presents a shortened egg reappearance period following the treatment with macrocyclic lactones (ivermectin or moxidectin) as compared to the previously published values. When these drugs were first marketed, the ERP was expected to be between 8-10 weeks for ivermectin and more than 13 weeks for moxidectin.
• This significantly alters the understanding and handling of strongyle infections in horses and could impact the administration of these drugs for the treatment of such infections.