EN
It has been found that tegument homogenate of Ascaris lumhricoides suis and also trypsin inhibitor isolated from it induce the Leghorn chick embryos mortality when injected into their yolk sac on 4th, 8th or 13th day of incubation. The trypsin inhibitor is one of important components of Ascaris homogenate causing mortality. There is linear interrelationship between the logarithm of dose of homogenate or trypsin inhibitor and the mortality of chickens in %. A significant decrease of mean mass of chicks injected with Ascaris homogenate or trypsin inhibitor in comparison with control groups was observed. There was more frequent occurrence of developmental abnormalities and pathological changes in groups of hatched chicks which received Ascaris homogenate or inhibitor.