Technology Description: This invention allows for detecting Mycobacterium bovis infection (e.g., tuberculosis) of cattle, white-tailed deer, elk, and potentially any mammalian species susceptible to M. bovis or M. tuberculosis infection. The invention is an in vitro assay which detects nitrite within leukocyte cultures that have been stimulated with M. bovis antigens. This invention solves several problems associated with tuberculosis diagnosis including a detection system that is cross reactive between various mammalian species, animals are handled only once to collect a blood sample, and expensive reagents are not required. With other tests animals are handled twice–once to inject the antigen and once to measure reactivity. This invention relies on measuring compounds produced in response to antigen presence. The compound is then detected with a simple assay, eliminating the need for developing expensive reagents. This assay is adaptable to tuberculosis eradication programs and, with modifications, for detecting infections by other pathogens. This assay could be used as a tuberculosis test for cattle, captive wildlife, and/or zoo animals. Biotechnology companies that develop analytical tests or measurement instruments, or assays using biomaterials could use this invention. Reference: Please refer to patent application USPN 6,673,566 (Docket #0152.01), "Diagnosis of Pathogen Infections Through Analysis of Nitrite Production by Antigen Stimulated Leukocytes," which issued on January 6, 2004. Inventors: Wade R. Waters Bacterial Diseases of Livestock Research Unit Ames, IA 50010 (515) 663-7756 / Fax: (515) 663-7458 rwaters@nadc.ars.usda.gov Mitchell V. Palmer (Same as first inventor) (515) 663-7474 / Fax: (515) 663-7458 mpalmer@nadc.ars.usda.gov