The efficacy of Exzolt (against all mite stages) compared to controls is summarized in Figure 5-5. The onset of efficacy was very fast, with an overall average mite reduction of 46.6% observed after the first night following the day of initial treatment (day 0; trap placed and mites collected for 24 hours). Efficacy was already 97.6% on day 3, achieved >97% by day 6, and persisted at that level for a lengthy period of time depending on the farm (100% efficacy at day 14 after the second Exzolt dose in 7/9 farms). A similar degree of fast and high onset of mite control efficacy was observed in all production types (layers, breeders, pullets) and housing systems.
The duration of mite population control following the 2-dose Exzolt regimen was assessed at the house level using a threshold of 90% reduction vs non-medicated controls (Figure 5-6). The duration of mite control was long and variable (2-8 months) and did not depend on the production type or the drinking water system, but was impacted by the duration of the remaining time until the end of the chicken production cycle and on the level of house separation of the compared groups. At 6 sites (L3, L4, B1, B2, P1, P2), no decrease of efficacy was observed until the end of the study (6 to 34 weeks; the 6-week efficacy of the pullet sites reflected the short remaining production cycle and shipment/ removal of the birds). Three sites (L1, L2, L5) experienced a regrowth of the mite population in the treated group after 8 to 18 weeks.
Regarding house separation, the presence of 2 rooms close to each other under 1 roof, separated by a wall but connected by an incompletely hermetic door, allowed faster mite regrowth in the treated house (in about 2 months) at sites L1 and L2 than that observed at farms with appropriately separated houses or rooms. Under real field conditions, the 2 houses would be treated at the same time. In 4 of the 5 layer and breeder farms with an appropriate separation between the study groups (sites L3, L4, B1, B2), the mite population was controlled until the end of the production cycle (16-34 weeks).
Mortality was low at most of the farms and comparable between the study groups before and after treatment. However, the acaricidal efficacy of Exzolt and resulting relief from mite infestation positively impacted the laying rate at 6 of the 7 layer or breeder farms, with a relative increase ranging from 0.9% to 12.6% (Figure 5-7). The sole site with reduced post-treatment lay rate (B1) had a known history of reduced performance in the house selected for treatment relative to the house used as a control. In regard to breeder performance, increased fertility and hatchability rates (2.8% and 1.7%, respectively) were observed at the B2 site, but no improvements were detected at the other B1 breeder farm (site houses not fully comparable for these parameters).
No adverse events related to the use of Exzolt were reported during the study.
The field study confirmed the high efficacy and excellent safety of Exzolt when administered in the drinking water (0.5 mg fluralaner/kg BW twice 7 days apart). Under commercial production conditions at 9 diverse layer, breeder, or pullet farms, Exzolt provided fast and persistent reductions in mite counts and positively impacted production parameters (rates of lay, fertility, hatchability). The 2-dose Exzolt regimen successfully controlled natural mite infestations for extended periods, far exceeding the time of actual drug administration (e.g., up to 34 weeks, or nearly 8 months, at 1 layer farm).