Canine leishmaniasis transmission: higher infectivity amongst naturally infected dogs to sand flies is associated with lower proportions of T helper cells

The dog is the main reservoir of Leishmania infantum, which is a parasite s pread among canine hosts by the bite of sand flies. Phlebotomus perniciosus is the sand fly acting as a major vector in the Mediterranean basin. As a consequence, the dog will suffer from leishmaniasis. In this work the infec tive capacity of infected dogs, established by direct xenodiagnosis, has be en investigated in relation to their immunological status by determining th e lymphocyte percentages present in peripheral blood mononuclear cells. We found a significant association between the percentages of T helper cells ( CD4/TcR alpha beta (+) and CD4/CD45RA(+)) and the infection rates detected in the vector, while significant association was not detected in the case o f the T cytotoxic cells (CD8/TcR alpha beta (+) and CD8/CD45RA(+)). The rel ationship discovered was that the lower the CD4(+) T cell count, the higher the rate of the infection in the vector. (C) 2000 Harcout Publishers Ltd.