Overview

• Protozoan-genus Leishmania; causes two types of disease: cutaneous: and visceral.
• Affected dogs in the United States invariably acquired infection in another country unless part of the endemic foxhound population.
• L. donovani infantum-Mediterranean basin, Portugal, and Spain; sporadic cases in Switzerland, northern France, and the Netherlands.
• L. donovani complex or L. braziliensis-endemic areas of South and Central America and southern Mexico.
• Considered endemic in foxhounds in the United States.
• Sandfly vectors-transmit flagellated parasites into the skin of a host. Vector unknown in United States.
• Cats-often localizes in skin.
• Dogs-invariably develop visceral disease; renal failure is the most common cause of death.
• Incubation period-1 month to several years.

Signalment

• Dogs-virtually all develop visceral (systemic), disease; 90% also have cutaneous involvement; no sex or breed predilection.
• Cats-cutaneous disease (rare); no sex or breed predilection.

Signs

Causes & Risk Factors

• Travel to endemic regions (usually the Mediterranean), where dogs are exposed to infected sandflies.
• Transmission by blood transfusion, in utero, and direct contact can occur.

Differential Diagnosis

• Visceral-blastomycosis; histoplasmosis; systemic lupus erythematosus; metastatic neoplasia; distemper; vasculitis.
• Cutaneous-other causes of hyperkeratosis.
• Skin biopsy-hyperkeratotic and nodular lesions; existence of organisms confirms diagnosis.
• Hyperglobulinemia-differentiate from chronic ehrlichiosis and multiple myeloma.

CBC/Biochemistry/Urinalysis

• Hyperproteinemia with hyperglobulinemia-nearly 100% of cases.
• Hypoalbuminemia-95% of cases.
• Proteinuria-85% of cases.
• High liver enzyme activity-55% of cases.
• Thrombocytopenia-50% of cases.
• Azotemia-up to 45% of cases.
• Leukopenia with lymphopenia-20% of cases.

Other Laboratory Tests

• Serologic diagnosis by IFA or ELISA available-most tests give cross-reaction to Trypanosoma cruzi; differentiate based on clinical signs, history, and likelihood of exposure. Rapid in-house immunochromatographic tests are also available.
• PCR-particularly sensitive on bone marrow, lymph nodes, spleen and skin, but also used to assess blood, bodily fluids, conjunctival scrapings, and histopathologic specimens.

Diagnostic Procedures

• Cultures-skin, spleen, bone marrow, or lymph node biopsies or aspirates; by the Centers for Disease Control and Prevention.
• Cytology and histopathology with immunohistopahtology-identify intracellular organisms in biopsies or aspirate specimens (listed above).

Pathologic Findings

• Cell infiltration (mainly histiocytes and macrophages) and characteristic intracellular amastigote forms especially in skin, lymph nodes, liver, spleen, and kidney.
• Mucosal ulcerations-stomach, intestine, and colon occasionally found.

Drug(s) Of Choice

• Sodium stibogluconate and meglumine antimonite may only be available from the CDC.
• Allopurinol-produces clinical cures but relapses occur. Best when used in combination with other drugs (meglumine or amphotericin B) as maintenance. Dose: 7 mg/kg PO q8h for 3 months, or 10 mg/kg/day PO for 2–24 months.
• Amphotericin B-0.5–0.8 mg/kg diluted in 50 mL dextrose 5% in water given IV over 1 minute q48h for total dose of 8–15 mg/kg.

Contraindications/Possible Interactions

• Seriously ill dogs-start antimonial drugs at lower doses.
• Renal insufficiency-treat before giving antimonial drugs; prognosis depends on renal function at the onset of treatment.
• Amphotericin B-nephrotoxicity can occur.

Zoonotic Potential

• Leishmaniasis is a notifiable disease reportable to the CDC.
• Advise owner of zoonotic potential.

Abbreviations

• ELISA = enzyme-linked immunosorbent assay
• IFA = immunofluorescent antibody test
• PCR = polymerase chain reaction