Canine Leishmaniasis : Clinical and Diagnostic Aspects

Canine leishmaniasis is a chronic parasitic disease transmitted by small bloodsucking insects. Clinically, affected patients present with progressive wasting, slight or marked reduction in appetite, lymphadenomegaly, splenomegaly, and cutaneous lesions (e.g., dry desquamation [dry seborrhea], ulcers, nodules). A correct diagnosis is based on specific serologic and molecular tests and nonspecific hematologic tests, which show principally normocytic, normochromic, poorly regenerative anemia and an increase in total serum protein levels associated with a polyclonal gammopathy. Leishmaniasis is a zoonotic protozoal disease caused by various species of the genus Leishmania. It is transmitted by small bloodsucking insects of the genera Sergentomyia, Warileya, Brumptomyia, Lutzomyia, and Phlebotomus. Leishmania is present in numerous countries in both the Old and New World. There are about 12 million cases of human leishmaniasis worldwide, and there are 400,000 to 1,200,000 new cases annually, principally in equatorial and subequatorial regions. The clinical features of the disease vary widely. In humans, it can be divided into visceral, cutaneous, and mucocutaneous forms. The clinical features in dogs are similar to those in the human visceral form associated with serious cutaneous complications. Dogs and humans are the principal definitive hosts. The principal etiologic agents responsible for visceral leishmaniasis are Leishmania infantum in the Mediterranean area and North America, Leishmania donovani and L. infantum in Asia (particularly in India and China) and Africa, and L. donovani and Leishmania chagasi/L. infantum in Central America (e.g., Brazil, Venezuela) (Figure 1). Isolated foci of canine visceral leishmaniasis have been recently reported in areas of the New World previously considered to be disease-free. Endemic canine leishmaniasis has also been rarely reported in the United States. The only reported autochthonous cases originated in Ohio, Texas, Maryland, and Oklahoma, and antileishmanial antibodies have been detected in asymptomatic CE 358 Vol. 25, No. 5 May 2003 www.VetLearn.com *A companion article on therapeutic aspects of the disease appears on p. 370 of this issue. n Canine leishmaniasis is a