Evaluation of neurobehavioral abnormalities and immunotoxicity in response to oral imidacloprid exposure in domestic chickens (Gallus gallus domesticus)

ABSTRACT

Domestic chickens (Gallus gallus domesticus) were exposed to imidacloprid by gavage once daily for 7 consecutive days at 0, 0.03, 0.34, 3.42, 10.25, and 15.5 mg/kg/day (n = 20 per group; 5 6-week-old males, 5 6-week-old females, 5 9-week-old males, and 5 9-week-old females). The severity and duration of neurobehavioral abnormalities were recorded. Components of the innate and adaptive immune system were assessed with 7 standard functional assays. Temporary neurobehavioral abnormalities were observed in a dose-dependent manner, including muscle tremors, ataxia, and depressed mentation. Based upon mean clinical severity scores, the no observed adverse effect level (NOAEL) was 3.42 mg/kg/day, and the lowest observed adverse effect level (LOAEL) was 10.25 mg/kg/day. The effective dose value for the presence of any neurobehavioral abnormalities in 50% of the test group (ED₅₀) was 4.62 ± 0.98 mg/kg/day. The ED₅₀ for an adjusted score that included both severity and duration of neurobehavioral abnormalities was 11.24 ± 9.33 mg/kg/day. These ED₅₀ values are equivalent to a 1 kg bird ingesting 29 or 70 imidacloprid treated soybean seeds respectively. Immunotoxicity was not documented, possible causes include the assays were insensitive, relevant immune functions were not examined, or imidacloprid is not immunotoxic at this dosing schedule in this species. Neurobehavioral abnormalities were a more sensitive indicator of the sublethal effects of imidacloprid than immunotoxicity.

KEYWORDS:

• Avian toxicity
• behavioral toxicology
• neurotoxicity
• neonicotinoids
• risk assessment

Acknowledgments

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). Special thanks to Carlie LaLone (United States Environmental Protection Agency) for assistance with the SeqAPASS data.

Disclaimer

This research does not reflect the official positions and policies of the United States Environmental Protection Agency. Mention of products/trade names does not constitute recommendation for us by the United States Environmental Protection Agency.

Declaration of interest

The authors have no financial, commercial, legal, or professional relationships to disclose that may generate a conflict of interest regarding this research.

Data availability statement

Data will be available upon publication of the manuscript at https://sciencehub.epa.gov/sciencehub

Supplementary Material

Supplementary data for this article can be accessed publisher’s website.

Additional information

Funding

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR);