<p>The present invention provides a formulation that prevents virulent Mycoplasma galHsepticum infection in birds of the order GaIHf ormes. The formulation comprises live Mycoplasma galHsepticum strain K5831 or derivatives thereof in a pharmaceutically acceptable carrier. A vaccine that prevents virulent Mycoplasma galHsepticum infection in birds of the order Galliformes is also presented. Methods for administering the formulation and vaccine are also presented.</p>
