EFFECT OF SUBCLINICAL LEAD TOXICITY ON THE IMMUNE-RESPONSE OF CHICKENS TO NEWCASTLE-DISEASE VIRUS-VACCINE

The effect of lead acetate (20 and 40 mg kg(-1) bodyweight daily) admi nistered via the crop from day old to 56 days of age on the immune res ponse to Newcastle disease virus vaccine (NDVV, La Sota strain) was st udied in 354 Lohman chickens. Lead decreased the mitogenic response of peripheral blood lymphocytes (PBL) to phytohaemagglutinin-P (pHA-P) i n birds vaccinated with NDVV. It also decreased the weights of the bur sa of Fabricius, the thymus glands and the spleen relative to bodyweig ht. Lead administration decreased the antibody titre to NDVV in the va ccinated groups. The percentage mortality due to a challenge with a vi rulent velogenic Newcastle disease virus was higher in the lead intoxi cated birds.