Effects of social stress on the toxicity of malathion in young chickens.

Thirty-eight 7-week-old white leghorn chickens of two strains (high and low antibody response to sheep erythrocytes) were divided into groups for exposure to high and low levels of social stress. They were then challenged orally with a toxic dose of the organophosphate insecticide malathion (250 mg/kg body weight) and evaluated 60 min later for muscarinic signs (diarrhea, lacrimation, respiratory secretions), nicotinic signs (muscle weakness), plasma cholinesterase activity, and brain acetylcholinesterase activity. A significant correlation was shown between clinical and biochemical indices of organophosphate toxicity. The correlation between social stress and malathion toxicity was less well defined. Chickens with low antibody response preexposed to high social stress were most resistant to organophosphate toxicity.