Fowl cholera: immunologic and werologic response in turdeys to live Pasteruella multocida vaccine administered in the drinking water.

Live fowl cholera vaccine administered in drinking water induced immunity in young turkeys against a challenge of a different immunogenic type of Pasteurella multocida; this is referred to as cross-immunity. Serum from the vaccinated birds induced passive cross-immunity in chicks and turkeys; this demonstrated that the cross-immunity induced with the drinking water vaccine was associated with the humoral system. Results of serologic tests with agar grown P. multocida indicate that agglutinins and precipitins are not associated with the induced cross-immunity. A live culture of P. multodica previously reported to induce cross-immunity in mature turkeys without causing adverse effects when administered in the drinking water, killed 6 of 45 (13 per cent) poults in the present study; this demonstrated that young turkeys are more susceptible to fowl cholera than mature turkeys.