Clinicopathologic and atypical features of naturally occurring leptospirosis in dogs: 51 cases (2000-2010).

OBJECTIVE: To determine clinicopathologic features, percentage of atypical abnormalities, antibody titers against Leptospira serogroups, and importance of convalescent titers in dogs with leptospirosis.
DESIGN: Retrospective case series. ANIMALS: 51 dogs with leptospirosis. PROCEDURES: Criteria for inclusion were at least 1 positive microscopic agglutination test (MAT) result (titer ≥ 1:1,600 in vaccinated dogs, titer ≥ 1:800 in nonvaccinated dogs, or ≥ 4-fold increase in convalescent titer), a complete medical record (including leptospirosis vaccination date, reason for initial evaluation, and CBC, serum biochemical analysis, and urinalysis results), and clinical signs or laboratory findings consistent with leptospirosis.
RESULTS: Initial clinical signs, temporal distribution, and signalment were similar to previous reports. Convalescent MAT titers were necessary for diagnosis in 45% of cases. Atypical abnormalities included radiographic evidence of pulmonary disease in 10 of 23 dogs and hepatic involvement alone in 7 of 51 dogs. Other abnormalities included proteinuria in 34 of 51 dogs, thrombocytopenia in 26 of 51, coagulopathy in 7 of 24 dogs, hypoalbuminemia in 14 of 51 dogs, and glucosuria in 9 of 51 dogs. Significant associations were found between antibodies against serogroup Grippotyphosa and renal involvement and serogroup Icterohaemorrhagiae and hepatic involvement. CONCLUSIONS AND CLINICAL RELEVANCE: Increased awareness of atypical abnormalities may decrease misdiagnosis of leptospirosis in dogs. Results of concurrent infectious disease testing should be interpreted with caution; misdiagnosis of leptospirosis could pose a public health risk. Convalescent titers were necessary to identify infection when acute testing results were negative. Further research is needed to determine the true associations between antibodies against identified serogroups and clinical features.