Successful resolution of natural Werneckiella equi infestation in two horses using pour-on Fipronil: A clinical observation

Werneckiella equi is an ectoparasite of equids, and control can be challenging because of the limited availability of licensed products. This case report describes the clinical observation of 1% fipronil pour-on against W. equi infestation in horses admitted to a veterinary hospital. Two horses were treated and observed between 2022 and 2023. Both exhibited pruritus, especially in the head, withers, and croup regions, and were diagnosed with severe W. equi infestation. The treatment consisted of a single topical application of 1% fipronil pour-on (1 mg/kg). Parasite reduction was assessed by complete physical examination, until complete parasite elimination. Demarcated areas were used for daily lice counts. Infestation was resolved within eight days (Horse 1) and twelve days (Horse 2), with no recurrence observed over six months. These preliminary observations suggest that 1% fipronil pour-on may offer a practical alternative for eliminating W. equi under clinical conditions, offering advantages such as minimized stress during application, precise dosing, and enhanced handler safety. However, due to the lack of a control group and small sample size, these results should be interpreted as preliminary clinical evidence.