leptospirosis

Introduction: The most common Leptospira serovars infecting dogs were reported to be canicola and icterohaemorrhagia in older studies, but pomona and grippotyphosa have been the most common isolated in recent studies. This shift may represent exposure of pet dogs to infected wildlife such as raccoons and opossums, which inhabit suburban and urban areas.

Clinical Findings: Dog of all ages may be affected, and there is no sex predilection. The incubation period is 4-12 days. Nonspecific signs such as fever, depression, anorexia, and generalized pain may be seen during this time. Vasculitis, thrombocytopenia, and coagulopathy may develop. Within a few days, additional signs of uremia such as dehydration, vomiting, and oral ulceration, are seen. The liver is variably affected, and the degree of icterus often reflects the severity of the disease. Meningitis, uveitis, and abortion have been rarely reported.

Hematologic abnormalities include leukocytosis, lymphopenia, monocytosis, and thrombocytopenia. Serum chemistry may reveal azotemia and electrolyte disturbances secondary to the renal failure, including hyponatremia, hypochloremia, and hyperphosphatemia. Serum levels of hepatic enzymes (AST, ALT, alkaline phosphatase) and serum bilirubin increases if the liver is affected. Urine sediment usually contains RBC, WBC, and granular casts. Isosthenuria, proteinuria, and glucosuria reflect tubular damage.

Lesions: In acute disease, the kidneys or liver, or both are swollen. Hemorrhages may be present in any organ. Other lesions may include any of those seen with acute uremia. In chronic cases, white or gray foci or streaks may be seen in the kidney and liver. Histologically, lesions in acute disease are those of acute uremia, including acute interstitial nephritis and possible hepatitis. In chronic disease, the only lesions may be chronic interstitial nephritis or chronic active hepatitis, or both.

Treatment: Renal failure and liver disease are treated with fluid therapy and other supportive measures to maintain normal fluid, electrolyte, and acid-base balance. Antibiotic therapy consists of penicillin, tetracycline, or doxycycline to eliminate leptospiremia, followed by tetracycline or doxycycline to eliminate the renal carrier phase. Tetracycline should be used with caution in azotemic animals. The fluoroquinolone antibiotics such as enrofloxacin also appear to be leptospirocidal.

Prevention/Prophylaxis: To reduce the chances of exposure, owners are advised to engage in rodent control and keep their dogs leashed. During epidemics, confinement to the owner's premises should be recommended. Bivalent bacterins are available and should be administered q6-8mo to maintain a protective titer for dogs at high risk, e.g., show, stud, or hunting dogs. If leptospirosis is diagnosed in a kennel, treatment and vaccination of all dogs in the kennel should be considered. Dogs in contact with wildlife should receive bacterins containing grippotyphosa and pomona antigens.

reprinted with kind permission from Roger Ross DVM
http://animalpetdoctor.homestead.com

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