Diagnosis can be made in the acute stage of infection by cultivation of bacteria or by molecular detection of organisms in biopsy samples of lymph node or ulcerated oral mucosa. Antibodies against F. tularensis may be detected by an indirect immunofluorescent antibody test (IFAT) or by haemagglutination testing. A fourfold increase in titre may be indicative of an acute infection; however, antibodies may only occur up to 3 weeks after acute infection. In antibodypositive animals culture and molecular detection is no longer possible, because by this time the organism will have been eliminated from the animal.