Canine Leptospirosis

Author: Andrèanne Clèroux, DVM, IPSAV, DACVIM (Internal Medicine)
Philadelphia Animal Specialty & Emergency 

The American College of Veterinary Internal Medicine recently published an updated consensus statement on canine leptospirosis, which you can find here. This monthly newsletter summarizes the pathophysiology, diagnosis, and treatment of this disease. 

Leptospirosis (Leptospira) is a zoonotic pathogen that is shed in the urine of infected hosts, the most common ones being rodents, and contaminates soil and water where it can remain viable for weeks to months. Infection occurs when the spirochete comes in contact with mucous membranes or abraded skin of dogs. It can also be transmitted via predation, bite wounds, and venereal and placental transfer. It is important to remember that all dogs are at risk of becoming infected with Leptospirosis, regardless of their age, breed, lifestyle, and the time of year and that vaccination is not 100% protective against this infection.

Most common hematological, biochemical, and urinalysis findings:

• Neutrophilia (27-94%), increased band neutrophils (3-81%)

• Lymphopenia (2-29%)

• Monocytosis (29-68%)

• Thrombocytopenia (14-73%)

• Mild to moderate non-regenerative anemia (18-92%)

• Increased BUN (54-100%) and creatinine (55-100%)

• Elevated ALP (19-94%), ALT (22-87%), and AST (28-69%)

• Hyperbilirubinemia (15-94%)

• Increased CK (44%)

• Increased troponin I (69-94%)

• Isosthenuria

• Glucosuria (18-83%)

• Cylindruria (8-67%)

• Proteinuria (28-81%)

Once a dog becomes infected the leptospires enter the bloodstream and will leave the vascular space and invade the host’s tissues potentially leading to a wide variety of organ involvement such as acute kidney injury, cholestatic hepatopathy, leptospiral pulmonary hemorrhage syndrome, coagulopathy, vasculitis, pancreatitis, ocular involvement, myocarditis, enteritis, and myositis. Acute kidney injury and cholestatic hepatopathy are generally recognized together but can sometimes be diagnosed independently.1 Leptospirosis should be considered in any dogs presenting with an acute kidney injury, especially when a cholestatic hepatopathy or pulmonary hemorrhage are present concomitantly. Because infection can quickly progress to an acute kidney injury, it should also be considered in dogs with acute onset of fever, especially if they are not vaccinated for leptospirosis. 

To optimize the diagnosis of leptospirosis both leptospirosis titers and PCR should be submitted whenever possible. Urine and blood PCR specimens should be collected before administration of antibiotics to optimize sensitivity of this test. 

Patients with suspected or confirmed disease should be treated with doxycycline (5mg/kg PO BID) for a duration of 2 weeks. Doxycycline is recommended to eliminate the intra-renal persistence of the organism. If the patient’s initial clinical status precludes the use of oral doxycycline the patient might be initially treated with IV ampicillin or PO amoxicillin to suppress bacteremia. As patients can present with a variety of symptoms, the medical management of these patients needs to be tailored to each individual and aim to ensure appropriate hydration, acid-base status, GI support, and nutritional support. Supplemental oxygen therapy and renal replacement therapy (hemodialysis) might be required in severe cases.
 

Dogs should be vaccinated yearly starting at 12 weeks of age to help prevent this disease. Following a documented infection a patient should be vaccinated as soon as possible after recovery due to risks of ongoing exposure/reinfection and to the fact that it is unknown whether natural infection results in life-long immunity. 

This information was adapted from the Updated ACVIM consensus statement on leptospirosis in dogs:

1. Sykes JE, Francey T, Schuller S, et al. Updated ACVIM consensus statement on leptospirosis in dogs. J Vet Intern Med 2023;37:1966-1982.