Age related susceptibility of newborn pigs to the cutaneous application of chlorpyrifos.

An aerosol preparation containing 2.5% chlorpyrifos was applied to the tail and umbilicus of newborn pigs. Mortality was 7/7 pigs treated 0-3 hr after birth, 3/5 pigs treated at 24-30 hr, and 0/3 pigs treated 30-36 hr after birth. Clinical signs consistent with organophosphate (OP) toxicosis were demonstrated by pigs that subsequently died or were euthanatized in extremis. Blood and brain cholinesterase (ChE) activities were depressed in affected pigs compared to controls. Only 1/3 pigs treated 30-36 hr after birth had a diagnostically significant depression in blood ChE. These results indicate that piglets one day or less of age are susceptible to OP toxicosis by cutaneous absorption of chlorpyrifos.