Leptospirosis is a zoonotic bacterial disease that is caused by the spirochete genus Leptospira. Leptospira species are spread through urine of infected animals, and exposure typically manifests as a chronic renal infection if left untreated. Leptospirosis can affect a wide range of animals, as most mammals are susceptible to infection. Often signs and symptoms of leptospirosis in companion animals can be non-specific and can range from lethargy to kidney and liver dysfunction. In ruminant animals, leptospirosis can cause reproductive complications, such as abortion or the birth of weak offspring.
In veterinary diagnostics, there are a few ways to test for leptospirosis. Each methodology has different turn-around times, appropriate sample types, and indications. At the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) there are two testing options offered: the microscopic agglutination test (MAT) and real time polymerase chain reaction (rt-PCR).
The Leptospira MAT is the gold standard test that uses blood serum to test for antibodies of specific Leptospira spp. serovars. At TVMDL, there are eight serovars offered for testing. These include pomona, icterohemorrhagica, canicola, grippotyphosa., hardjo, bratislava, autumnalis, and sejroe. These eight serovars are considered pathogenic, as opposed to other Leptospira sp. that are considered saprophytic (non-pathogenic). Testing can be requested for a combination of the eight serovars as a panel, or individually. The Leptospira MAT test can indicate current infection, past infection, or vaccination and will provide a titered result. The test cannot differentiate between active infection or previous exposure/vaccination. The submittal of paired acute and convalescent samples can be useful in identifying the stage of infection or vaccination efficacy.
Samples such as urine or fresh tissue (kidney, liver, or placenta) can be tested for the presence of Leptospira DNA by using rt-PCR. This test allows TVMDL to determine if there is the specific 16S Ribosomal RNA gene target sequence within the specimen. This detection of DNA is useful for identifying current infection or a chronic carrier state, as opposed to the Leptospira MAT that identifies immune response. Leptospirosis continues to be a significant concern in veterinary medicine due to its zoonotic potential and its non-specific signs and symptoms, which can be easily missed. Accurate and timely diagnosis is important to prevent transmission, manage infection and help veterinarians know what steps to take for treatment. To learn more about leptospirosis, TVMDL offers information and case studies at tvmdl.tamu.edu