A Leishmania donovani-complex specific DNA probe was used
to confirm the widespread dissemination of amastigotes in apparently
normal skin of dogs with canine visceral leishmaniasis. When
Lutzomyia longipalpis were fed on abnormal skin of five
naturally infected dogs 57 of 163 (35%) flies became infected: four
of 65 flies (6%) became infected when fed on apparently normal skin.
The bite of a single sandfly that had fed seven days previously on a
naturally infected dog transmitted the infection to a young dog from
a non-endemic area. Within 22 days a lesion had developed at the
site of the infective bite (inner ear): 98 days after infection
organisms had not disseminated throughout the skin, bone marrow,
spleen or liver and the animal was still serologically negative by
indirect immunofluorescence and dot-enzyme-linked immunosorbent
assay. When fed Lu. longipalpis were captured from a kennel
with a sick dog known to be infected, 33 out of 49 (67%) of flies
contained promastigotes. In contrast only two infections were
detected among more than 200 sandflies captured in houses. These
observations confirm the ease of transmissibility of L. chagasi
from dog to sandfly to dog in Teresina. It is likely that canine
VL is the major source of human VL by the transmission route
dog-sandfly-human. The Lmet2 DNA probe was a useful epidemiological
tool for detecting L. chagasi in sandflies.
