Quail study links imidacloprid to reproductive and DNA damage

Chronic imidacloprid exposure caused a broad cluster of reproductive, behavioral, endocrine, and genotoxic effects in Japanese quails in a newly posted Frontiers in Veterinary Science paper, adding fresh evidence that neonicotinoid exposure can affect non-target birds well before death becomes the defining endpoint. The study found delayed puberty, suppressed reproductive hormones, reduced courtship and mating behavior, lower egg production, and DNA damage in hepatic and cerebral tissue, while also highlighting sickness behavior and sexual behavior dysfunction as potential early warning signals of exposure. (frontiersin.org)

That framing matters because imidacloprid has long been scrutinized for avian risk, but much of the regulatory and public discussion has centered on acute toxicity, pollinators, or broad ecological effects rather than subtle reproductive and neuroendocrine changes. Japanese quail are a standard model in ecotoxicology and behavioral neuroendocrinology, and prior work has made them useful for studying reproductive endpoints that may be missed in narrower survival-based assessments. Earlier quail studies have already linked imidacloprid with biomarker changes consistent with neurotoxicity, oxidative stress, and genotoxicity, while broader reviews have associated neonicotinoid use with direct and indirect risks to birds. (frontiersin.org)

In the new study, El-Shoukary and colleagues evaluated chronic oral imidacloprid exposure during weeks 7 through 12 of age. According to the abstract, exposed birds reached sexual maturity later and at higher body weights, while showing persistent reductions in brain-somatic and gonado-somatic indices. Endocrine testing showed suppression of FSH, LH, testosterone, progesterone, and total estrogens, alongside dysregulation of estradiol. Male quails had reduced cloacal gland area, lower foam production, and impaired courtship and copulatory performance. Females showed reduced proceptive behavior and marked declines in weekly egg production, egg weight, hen-day egg production, and total egg mass. The authors also reported significant DNA damage on alkaline comet assay in liver and brain tissue. (frontiersin.org)

The paper also fits into a broader evidence base suggesting that avian effects from imidacloprid can be both behavioral and systemic. A 2022 quail study indexed in PubMed found changes in cholinesterase activity, liver enzymes, oxidative stress markers, and nucleic acid content after oral sublethal dosing, supporting the idea that behavioral changes may reflect wider physiological injury rather than isolated neurologic signs. Reviews of neonicotinoid exposure in birds have also pointed to reduced food consumption, weight loss, sperm effects, and biodiversity declines associated with agricultural use, though field translation remains complex and species-specific. (pubmed.ncbi.nlm.nih.gov)

On the regulatory side, the findings land in an environment where imidacloprid remains under active ecological scrutiny. EPA has said it is reviewing neonicotinoids on a class-consistent timeline, released preliminary ecological risk assessments for imidacloprid, and in June 2022 issued a final biological evaluation for listed species from labeled uses. EPA documents tied to registration review have also described elevated risk quotients for some bird exposure scenarios, especially among smaller birds. The new quail data do not by themselves change regulation, but they add mechanistic detail that could become relevant as agencies weigh how well current frameworks capture sublethal reproductive and behavioral harm. (epa.gov)

Why it matters: For veterinarians, the practical takeaway is that pesticide exposure in birds may first show up as changes in behavior, breeding performance, or condition, not just classic acute toxicosis. Clinicians working with backyard flocks, aviary birds, wildlife, or rehabilitation cases may want to keep environmental exposure histories in mind when birds present with reduced activity, altered drinking behavior, reproductive failure, or poor breeding performance. For veterinary toxicologists and public health professionals, the study reinforces the value of looking beyond mortality-based endpoints toward endocrine and reproductive markers that may better reflect real-world, lower-dose exposure patterns. (frontiersin.org)

What to watch: The next step is whether follow-on studies validate these early warning behavioral markers in other avian species or under field-realistic exposure conditions, and whether regulators incorporate more sublethal reproductive and neurobehavioral endpoints into imidacloprid risk assessment. (frontiersin.org)