Effect of levamisole on the response of broilers to coccidiosis vaccination.

The effect of levamisole on the response of commercial broilers to coccidiosis vaccination was assessed. The concentration, frequency, and timing of levamisole were varied in three separate experiments to determine optimum conditions for potentiating the response of broilers to a single oral dose of commercial coccidiosis vaccine at 7 days of age. In all instances, levamisole was found to improve development of immunity to coccidiosis. Birds that received levamisole by intraperitoneal (IP) injection had better weight gains for 3 weeks following coccidiosis vaccination and improved resistance to challenge with Eimeria tenella when compared with vaccinated chickens that did not receive levamisole. However, levamisole given at .25 mg/kg body weight by IP injection 3 days prior to the coccidiosis vaccine resulted in the greatest potentiation of the immune response. Performance parameters following challenge included weight gain, oocyst production, fecal droppings, and livability. Findings confirm and extend observations regarding the ability of levamisole to potentiate vaccination responses in chickens.