Delayed neurotoxicity of O-ethyl O-4-cyanophenyl phenylphosphonothioate (cyanofenphos) in hens

The injection of the delayed neurotoxin tri-O-tolyl phosphate into embryonating chicken eggs and its effects on subsequent chick development

Tri-o-tolyl phosphate (TOTP) was injected into the yolk sac of 120-h chicken embryos at concentrations equivalent to 200,100, 50, 25, or 0 (vehicle control) microgram TOTP/g egg. On d 22 of incubation, all live hatchlings were wing-banded, weighed, and housed in a brooder battery according to treatment level. Birds were examined daily for mortality as well as for development of clinical signs indicative of delayed neurotoxicity. Body weights were determined at weekly intervals for 4 wk. At the end of the fourth week, all birds were killed and necropsied. Liver, spleen, bursa of Fabricius, ovary or testes, and comb (male only) were removed and weighed. The injection of 200 microgram TOTP/g egg significantly depressed hatchability when compared to controls. Chick mortality was not significantly affected by TOTP injection. Clinical symptoms characteristic of delayed neurotoxicity did not develop during the 4-wk observation period. TOTP injection caused a transient growth depression that disappeared by 4 wk of age in both sexes. Organ weighs at 4 wk of age were not consistently affected by the treatment.