The delayed neurotoxic effects of triphenyl phosphite (TPP) in the Japanese quail

Certain organophosphorus chemicals (OPs) cause a condition called organophosphorus-induced delayed neurotoxicity (OPIDN). Since previous studies indicated Japanese quail were resistant to Type I OPIDN compounds, the purpose of this study was to determine the sensitivity of this species to triphenyl phosphite (TPP), a Type II OPIDN compound. Quail were administered single subcutaneous doses of TPP at concentrations up to 500 mg/kg. At 24 hrs after dosing, half of the birds from each dose group were assessed for whole-brain neurotoxic esterase (NTE) activity. The remaining birds were observed daily for up to 20 days for the development of OPIDN clinical signs. Brains from some of these birds were examined for degeneration. All doses of TPP resulted in NTE inhibition which ranged from 11% to 87% and clinical signs as soon as 3 days post-dosing. Widespread degeneration in the brain was also noted.