Paired acute and convalescent samples are preferred from most animals, and rising antibody titers are usually seen in acute cases. Single samples with high titers increase the suspicion of leptospirosis, although they are not definitive. However, a single positive sample from an aborted fetus is diagnostic. Herd tests are often used in ruminants. The most commonly used serological tests in animals are the microscopic agglutination test (MAT) and enzyme-linked immunosorbent assays (ELISAs). The MAT evaluates antibody responses to a selection of Leptospira serovars (often 5-7 in veterinary assays). This test is serogroup but not serovar specific, although it may suggest a likely serovar. False negatives are possible if the infecting serogroup was not included in the MAT panel. ELISAs, including a bovine milk ELISA, are available for some species of animals.