Antigestational effects of Icon (R) , a pyrethroid insecticide on mid pregnancy of rats

Icon (R) is a water miscible type II synthetic pyrethroid insecticide based on active ingredient lambda cyhalothrin (10% w/v). It was recently introduced to Sri Lanka as an indoor spray against malaria vector mosquitoes. The aim of this study was to ascertain the potential effects of Icon (R) on pregnancy outcome of rats when exposed during mid pregnancy (days 8 -14). Icon (R) was orally administered daily during this period in three different doses: 63, 83, 125 mg/kg body wt./day of Icon (R) (active ingredient; lambda cyhalothrin ; 6.3, 8.3, 12.5 mg/kg/day) respectively. Several parameters of reproduction, pre- and post-natal development were monitored. The results demonstrated that Icon (R) is detrimental to pregnancy outcome (in terms of number of uterine implants, number of viable implants, post implantation loss, number of pups born, litter index, and foetal survival ratio) but induced no changes in gestational length, gross morphological birth abnormalities or detectable pre- and post- natal developmental impairments. The anti-reproductive effects of Icon (R) were mediated by multiple mechanisms (hypophagia, maternal toxicity, stress, uterine myotropic activity, embryofoetoxicity, anti-progestrogenic activity, inhibition of decidualizaton process, abortifacient activity and vaginal bleeding) leading to enhancement of postimplantation losses. It is concluded that exposure to Icon (R) during mid gestation poses a considerable threat to pregnancy of rats.