Distribution of fluralaner in plasma and liver in broiler breeder hens and roosters following the administration of fluralaner (Bravecto®) via medicated drinking water

Bed bugs have become resistant to traditional insecticides, and the demand for effective drugs to eradicate bed bugs on poultry farms (especially table-egg layer) and breeder farms (especially broiler breeders) is growing. Fluralaner has been shown to be effective in treating bed bug infestation in poultry. However, there is no product containing fluralaner labeled for use in chickens in the United States. In the present study, we prepared medicated drinking water using fluralaner dog chews (Bravecto®) and diethylene glycol monoethyl ether (Transcutol V). The present study aimed to determine the plasma pharmacokinetic profile and residues in liver as well as any adverse effects related to drug administration. All chickens were orally treated with fluralaner via medicated drinking water including 0.2 % (V/V) Transcutol V for 6 hours. The fluralaner dosage regimen was 0.5 mg/kg/day, twice, 7 days apart. Sparse blood collection was conducted after the first dose and tissue collection was performed the day after the second dose. The fluralaner concentrations in plasma and liver were determined using Ultra Performance Liquid Chromatography with tandem Mass Spectrometry detection (UPLC/MS/MS). Fluralaner was dissolved completely in drinking water including 0.2 % (V/V) Transcutol V with 98 % recovery with some degradation of fluralaner confirmed over time. The highest fluralaner concentration (0.56 µg/mL) in plasma was observed 24 hours after removing the first dose. Fluralaner concentrations in plasma exceeded the 50-90 % lethal concentrations of bed bugs for 168 hours following the onset of the first dose. The mean fluralaner concentration detected in the liver was 1.25 µg/g at 21 hours after removing the second dose. No visual adverse effects were observed during the entirety of the study. Enlarged kidneys were observed by gross necropsy and mild multifocal, small aggregations of lymphocytes in the parenchyma and mineralization of a few tubules in kidneys were found on histopathological examination. However, it was unclear these findings were related to drug administration. This dosing method might be helpful in controlling bed bug infestations in poultry facilities.