ELISA for detection of anti-Toxocara IgY and avidity in infected chickens. Experimental infection of chickens with 100, 1000 and 5000 embryonated T. canis eggs. High levels of IgY and high avidity index in the chronic phase of infection. Influence of infective dose on the humoral immune response. ELISA is a useful tool for seroprevalence studies in poultry.