Canine Leptospirosis Update

Shawn Kearns, DVM, DACVIM (SAIM), Angell Animal Medical Center, Boston, Massachusetts

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In the Literature

Knöpfler S, Mayer-Scholl A, Luge E, et al. Evaluation of clinical, laboratory, imaging findings and outcome in 99 dogs with leptospirosis. J Small Anim Pract. 2017;58(10):582-588.


Leptospira spp of various serovars are responsible for human and animal leptospirosis infections worldwide. Leptospirosis remains an important zoonotic disease. Clinical signs vary depending on geographic region and predominating serovar(s). Disease should be suspected in patients with presence of common serum chemistry findings, including azotemia, increased liver enzymes, and/or hyperbilirubinemia. Leukocytosis, anemia, and thrombocytopenia are often found on CBC. Disease is confirmed with single microscopic agglutination titers ≥1:800 for nonvaccinal serovars, a 4-fold increase in microscopic agglutination titers over 2 to 3 weeks, or urine and blood PCR testing. Blood-based PCR can detect organisms in the first 10 days of infection, after which concentrations are highest in urine.1 PCR tests are not influenced by vaccination,2 but prior antibiotic administration can decrease sensitivity. Use of an immunoglobulin M-based screening test may also be useful for earlier detection.3

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Although renal and hepatic involvement are most frequently reported, clinicians should be aware of potential for mild-to-severe pulmonary involvement. Multiorgan involvement of various combinations is common. Signs associated with lung involvement may be present at various times during disease progression. Thoracic radiographs should be obtained at initial presentation and if respiratory signs change during hospitalization. In this retrospective study, the medical records of 99 dogs with leptospirosis showed that 49% had pulmonary abnormalities detected on admission; nonsurviving patients more often had severe radiographic changes. 

Treatment of leptospirosis includes amoxicillin-based drugs and doxycycline. Most patients require additional supportive care with IV fluids, gastroprotectants, and antiemetics. Those with pulmonary involvement may require oxygen therapy, and those with severe azotemia, those with significant metabolic abnormalities, or those progressing to oliguria or anuria may require hemodialysis. Patients requiring hemodialysis have a more favorable outcome than do patients receiving hemodialysis for other known or unknown causes.4,5 Although many patients with leptospirosis can respond to treatment, the mortality rate can still be high, as represented by the 32% mortality rate in this study. Owners should be aware that multiorgan involvement, particularly in dogs with pulmonary manifestations, and more severe azotemia are factors associated with nonsurvival.

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Key pearls to put into practice:


Because timing of Leptospira spp infection is often unknown, a combination of serologic and PCR testing at initial presentation may increase the likelihood of diagnosis.



Prognosis is more guarded for patients with more severe azotemia, multiorgan involvement, and pulmonary involvement.



If financially and geographically feasible, early referral for hemodialysis should be considered in patients not responding to conventional medical management.


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