Detection of Leishmania infantum in canine peripheral blood.

Canine leishmaniosis is a severe systemic disease caused by Leishmania species parasites, which are transmitted by the bite of haematophagous phlebotomine sandflies. Dogs are a major reservoirs host for human visceral leishmaniosis. An 11-year-old male pinscher was referred during February 2004 with a one-month history of gastrointestinal disorders. Haematological analysis revealed a normochromic-normocytic hyporigenerative anaemia and leucocytosis with neutrophilia. May-Grunwald-Giemsa-stained peripheral blood smears revealed inside neutrophils numerous L. infantum amastigotes. Many free parasites were also observed. The immunofluorescent antibody test for Leishmania-specific antibodies yielded a positive titre of 1/320. The finding of Leishmania species amastigotes in peripheral blood is rare. The role of played by PMN in controlling leishmanial infection is still unclear. Experimental studies suggest a possible dual role for PNMs in the early response to the infection. On one hand, PMNs can rapidly eliminate the intracellular parasite; however, Leishmania species can survive intracellularly for the first hours or days after infection within PMNs, that may be vehicles for the transport of the parasite in blood.