The present invention provides novel isolated nucleic acids encoding antigenic proteins derived from Sarcocystis neurona, or unique fragments thereof. In particular, the invention provides novel isolated nucleic acids encoding membrane-associated polypeptides SnSAG2, SnSAG3, and SnSAG4. Also provided are purified antigenic polypeptide fragments encoded by the novel nucleic acid sequences set forth herein that encode for SnSAG2, SnSAG3, and SnSAG4. Also provided are isolated nucleic acids capable of selectively hybridizing with the nucleic acid from Sarcocystis neurona. The invention also provides vectors comprising the nucleic acids of the invention encoding an antigenic protein derived from Sarcocystis neurona or a unique fragment thereof and provides the vector in a host capable of expressing the polypeptide encoded by that nucleic acid. Finally, the invention provides purified polyclonal and/or monoclonal antibodies specifically reactive with Sarcocystis neurona and a method of detection of Sarcocystis neurona utilizing the antibodies of the invention.