Fipronil administration in laying hens: Edible and inedible tissue residue profiles

Abstract

Introduction: Fipronil (FIP) is a pyrazole insecticide authorized to control ectoparasites in small animals (worldwide) and cattle (in some countries). Few approved antiparasitic compounds are available for poultry. As consequence, the extra-label use of FIP has been described in this species to control the red mite Dermanyssus gallinae, an ectoparasite that constitutes an important health problem with huge economic repercussions in this production. Since FIP and its fipronil sulfone (FIP-SO2) metabolite residue profiles in eggs after administration to laying hens have been reported, the main goal of the current study was to investigate the FIP and the FIP- SO2 metabolite residues profiles in edible and other tissues after extra-label administration in laying hens. -Materials and Methods: Hens were extra-labelled treated with FIP (ECTOLINE® 1%) in feed and by the topical route. Following animal welfare standards, the animals were slaughtered at different times for a 60 day post-treatment period. Plasma, muscle, liver, kidney, fat, skin, feather, and feces samples were collected and analysed to quantify FIP and FIP- SO2 metabolite residues by UFLC-MS/MS. -Results and conclusions: FIP and FIP-SO2 residues were quantified in all tissues after both administrations to laying-hens. The FIP-SO2 residues were the highest in most tissues. After oral administration in feed, FIP was quantified mainly in feathers (maximum residue level (Cmax) of 0.24±0.16 µg/g at 9 days post-treatment (tmax), and fat (Cmax= 0.49±0.46 µg/g; tmax= 6 days). The highest FIP-SO2 residue profiles were found in fat (Cmax= 9.9±4.2 µg/g; tmax= 15 days), skin (Cmax= 1.7±0.6 µg/g; tmax= 9 days), and liver (Cmax= 1.1±0.5 µg/g; tmax= 6 days). Meanwhile, after topical administration, the highest residues were for FIP in feathers (Cmax= 17.6±5.3 µg/g) at 5 days post-treatment. High FIP-SO2 residues were also quantified in feathers (Cmax= 2.2±1.7 µg/g; tmax= 5 days), fat (Cmax= 1.8±0.8 µg/g; tmax= 15 days), and skin (Cmax= 0.44±0.1 µg/g; tmax= 15 days). It is important to consider in poultry production that laying hens that finish their productive period are intended for consumption. These results show that the consumption of edible tissues from treated chickens could have undesirable effects on health. Fortunately, low concentrations were found in muscle. Future studies applying the risk analysis tool will allow us to conclude whether or not there is a possible risk to consumers.