Between 90-95% of current cases of leptospirosis present clinically as a renal disorder only, both renal and hepatic disorders, or a hepatic disorder only. One cat with acute renal failure was diagnosed with the L. hardjo serovar. One dog presented with seizures and interictal signs and a leptospira PCR was positive on brain tissue. Bilateral uveitis cases should be screened for leptospirosis. Rarely, the presentation can mimic autoimmune hemolytic anemia with red blood cell hemolysis and bilirubinemia and bilirubinuria. Infected dogs with liver disease have increased concentrations of ALT, AST, +/- ALK, +/- GGT and occasionally have increased bilirubin. Liver biopsies showed periportal infiltrates with neutrophils and lymphocytes, necrosis and hemorrhages. The usual serovar identified in these cases is L. grippotyphosa. The current recommendation is to screen dogs with chronic renal failure or increased liver enzyme concentrations for all 7 leptospira serovars.

More cases are being reported with the L. bratislava and L. autumnalis serovars. The L. canicola serovar has not gone away and may be identified in random cases. Also, the presentation of disease has changed with more vasculitis and hepatitis cases seen, and minimal or absent signs of renal disease. The type of vasculitis seen is pneumonia presenting with a mild cough; the dogs have pulmonary edema and vasculitis. This vasculitis is seen often in people. Dogs can be clinically normal or have PU/PD or abnormal urine sediments.

The gold standard for diagnosis is still the presence of organisms revealed by silver stain of infected tissue.

Serologic screening should include all 7 leptospira serovars. The definitive serologic assay is the microagglutination test (MAT), which is best performed on paired sera, taken more than 14 days apart, especially if the animal has been vaccinated. The paired assays should be run at the same time [diagnostic laboratories should keep samples that initially test positive for 30 days.] Titers will vary in infected dogs, if treatment is initiated. For example, if the antibody titer is rising and doxycycline therapy is initiated, the titer could double in 5-7 days from 1:1600 to 1:3200, whereas without treatment it could be >1:6400. If no treatment is given, antibody titers typically will remain elevated for 6-8 months post-infection.

Urine screening for Leptospira spp. by fluorescent assay (FA) or PCR can help in making a diagnosis or in detecting dogs that are shedding spirochetes in their urine.

Subsequent to booster vaccination with leptospirosis vaccines from Fort Dodge Animal Health, antibody titers typically increase dramatically but then decline to approximately 1:800 four weeks after vaccination. Titers are low or negative one year post-vaccination, although challenge studies with the serovars L. icterohemorrhagiae and L. pomona have shown that these dogs are still protected against infection.

Vaccination titers can be cross-reactive with other leptospira serovars, but they are not cross-protective against serovars not in the vaccine.

The standard treatment with doxycycline is 5mg/kg BID for 2-3 weeks. It is unlikely that infected dogs would shed organisms after this treatment period. In people, 30 days of doxycycline eliminates urine shedding of Leptospira spp.
[Material for this topic was provided by Dr. Steve Barr]