The recommended treatment regimen for Exzolt (0.5 mg/kg BW twice at a 7-day interval) was identified as a result of a comprehensive dose-determination program that evaluated multiple doses and durations using artificial infestations of poultry red mites under experimental conditions. Clinical data demonstrating the efficacy of Exzolt against natural infestations in layers, breeders, and pullets was subsequently generated from 4 studies:
- Three EU-based dose-confirmation studies were designed to confirm under field conditions the dose and frequency of treatment with Exzolt that was needed for efficacy against natural infestations with D. gallinae. Because the earlier dose-determination studies showed that the frequency of treatment is also relevant for efficacy, the dose-confirmation studies focused on 2 treatments at a 7-day interval.
- An extensive 9-site field study assessed the efficacy of Exzolt for chickens reared under commercial production conditions.
Treatment Regimen Rationale
The objective of dose-determination studies was to select a treatment regimen (dose, number of administrations, and administration interval) that provides efficacy (killing activity) against poultry red mites that feed on Exzolt-treated chickens. The duration of efficacy was intended to cover a period that is needed for the completion of 2 consecutive mite life cycles – a duration of at least 15 days.
Mite development from egg to the first blood-feeding stage (hematophagous protonymphs) normally occurs within 3 to 5 days (Figure 1-2), and a blood meal is required for further development of protonymphs to deutonymphs and adults, and also for production of mite eggs. Therefore, the target efficacy duration (~15 days) ensures that all non-blood-feeding mite development stages present at the time of first Exzolt administration will eventually ingest fluralaner once they develop into a blood-feeding stage.