Estimation of the Effects of Neonicotinoid Insecticides on Wild Raccoon, Procyon lotor, in Hokkaido, Japan: Urinary Concentrations and Hepatic Metabolic Capability of Neonicotinoids

Abstract

Toxicological effects of neonicotinoid insecticides (NNIs) have been reported for mammals, such as humans, rats, and mice. However, there are limited reports on their toxic effects on wild mammals. To predict NNI‐induced toxic effects on wild mammals, it is necessary to determine the exposure levels and metabolic ability of these species. We considered that raccoons could be an animal model for evaluating NNI‐induced toxicities on wildlife because they live near agricultural fields and eat crops treated with NNIs. The objective of the present study was to estimate the effects of NNI exposure on wild raccoons. Urinary concentrations of NNI compounds (n = 59) and cytochrome P450‐dependent metabolism of NNIs (n = 3) were evaluated in wild raccoons captured in Hokkaido, Japan, in 2020. We detected either one of the six NNIs or one metabolite, including acetamiprid, imidacloprid, clothianidin, dinotefuran, thiacloprid, thiamethoxam, and desmethyl‐acetamiprid in 90% of raccoons (53/59); the average cumulative concentration of the seven NNI compounds was 3.1 ng/ml. The urinary concentrations were not much different from those reported previously for humans. Furthermore, we performed an in vitro assessment of the ability of raccoons to metabolize NNIs using hepatic microsomes. The amounts of NNI metabolites were measured using liquid chromatography–electrospray ionization–tandem mass spectrometry and compared with those in rats. Raccoons showed much lower metabolic ability; the maximum velocity/Michaelis–Menten constant (Vmax/Km) values for raccoons were one‐tenth to one‐third of those for rats. For the first time, we show that wild raccoons could be frequently exposed to NNIs in the environment, and that the cytochrome P450‐dependent metabolism of NNIs in the livers of raccoons might be low. Our results contribute to a better understanding of the effects of NNIs on raccoons, leading to better conservation efforts for wild mammals. Environ Toxicol Chem 2022;41:1865–1874. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Pesticide Contamination Levels in the Stomach Contents of Wild Raccoons (Procyon lotor) and Masked Palm Civets (Paguma larvata) in Japan

“…Analysis of stomach contents revealed that raccoons in the croplands of Hokkaido were exposed to a variety of pesticides, with high concentrations of neonicotinoid insecticides like imidacloprid, acetamiprid, and clothianidin. The concentrations of neonicotinoid insecticides in the stomach contents were found to be comparable to those identified in urine samples (Shinya et al, 2022). A significant difference in pesticide concentrations was observed between raccoons that ingested corn and those that did not, underscoring the importance of corn as a substantial contributor to pesticide exposure for raccoons inhabiting croplands.…”

“…However, no significant difference was observed in pesticide concentrations based on the sex and age of the raccoons. When pesticide detection rates in stomach contents from the present study were compared with urine samples from our previous study (Shinya et al, 2022), the following trends were consistent in both matrices: higher detection rates of the following neonicotinoid compounds than others, such as imidacloprid (41.46% in stomach contents vs. 23.37% in urine), acetamiprid (39.02% vs. 35.59%), and clothianidin (36.59% vs. 66.10%), followed by thiamethoxam (12.20% vs. 18.64%); however, both thiacloprid (0% vs. 3.39%) and nitenpyram (0% vs. 0%) were not detected in the stomach contents (Table 3). Regarding dinotefuran (2.44% vs. 20.34%), stomach contents exhibited a notably low detection rate, whereas in urine, its detection rate was comparable to that of imidacloprid (23.37%).…”

“…Forty-one raccoons were captured from croplands in Hokkaido, Japan, between April 2021 and September 2022, utilizing box trap systems (Havahart Large Collapsible Pro Cage Model 1089; Woodstream), as described in our previous study (Shinya et al, 2022). Anesthesia was administered to the raccoons through a combination of butorphanol tartrate (Vetorphale, 1.2 mg/kg; Meiji Seika), medetomidine hydrochloride (Dolbene, 40 µg/kg; Kyoritsu), and midazolam (Dormicum, 0.2 mg/kg; Astellas) via intramuscular injection.…”

“…Our study aimed to evaluate the presence of neonicotinoid insecticides in the stomach contents of raccoons in the Hokkaido region of Japan. This assessment was conducted to compare the neonicotinoid insecticide concentrations previously quantified in urine samples collected from raccoons in the same region (Shinya et al, 2022).…”

“…Notably, neonicotinoid insecticides have been detected in raccoon urine in our previous study (Shinya et al, 2022). Given that raccoons and masked palm civets are recognized as invasive alien species in Japan and control programs have been implemented (Iwama et al, 2017;Suzuki & Ikeda, 2019), we were able to obtain fresh samples for analysis.…”