Trans-ovo permethrin exposure in quail (Cortunix japonica)

Permethrin is a commonly used, highly effective pesticide in poultry
agriculture, and has recently been trialed in conservation efforts to
protect Galá​pagos finch hatchlings from an invasive ectoparasite.
Although permethrin is considered safe for adults, pesticides can have
health consequences when animals are exposed during early life stages. The
few studies that have examined permethrin’s effects in embryonic chicks
and rats have shown hydrocephaly, anencephaly, reduced cellular energy
conversion, and disruption of developing heart muscle. To test
whether trans-ovo exposure of permethrin affects early
development in birds, we exposed Japanese quail (Coturnix japonica) eggs
to cotton treated with 1% permethrin that was incorporated into nests in
two amounts (0.2, 0.8 g), each with a paired untreated cotton control
group. When measured on incubation day 15, we found permethrin-treated
developing birds were smaller and showed signs of microcephaly, although
mortality rates were the same. Despite no difference in heart mass,
ventricular tissue was less compact, cardiac arteries were reduced and
heart rates were slower in permethrin-treated birds. Differences in heart
development were also observed at 5 days of incubation, indicating that
abnormalities are present from early in cardiac development. Future
studies are needed to examine permethrin’s effects on developmental
pathways and to determine if these effects persist after hatching to
affect offspring health. This study provides evidence that permethrin can
cross the eggshell to cause non-lethal but adverse effects on embryonic
development, and studies should look beyond hatching when monitoring the
efficacy of permethrin on wild bird populations.