About THE PROJECT
Visceral leishmaniasis (VL) known as
Kala-Azar is a very serious disease caused by Leishmania donovani
parasites. An estimated 500,000 VL cases occur annually, mostly in
India, East Africa and Brazil. In Africa, the worst affected regions
are southern Sudan, with estimated 15,000-20,000 cases annually and
Ethiopia with 4,000-5,000 diagnosed VL cases a year. Kala-Azar is
considered an emerging disease in Ethiopia where it is frequently
associated with AIDS, a leading cause of adult illness and death in
that country. Untreated, Kala-Azar is usually fatal, but with
appropriate treatment patients can recover.
with Visceral Leishmaniasis – South Ethiopia
Aims of the project include: To
study the ecology, population dynamics and behavior of the sand fly
vectors of VL in relation to seasonal and nocturnal activities of
villagers. To identify and characterize productive sand fly larval
breeding habitats. To determine which populations comprise significant
sources of infection for sand flies (xenodiagnosis). Is zoonotic
transmission important for maintaining the disease? To
characterize L. donovani causing distinct pathologies and
determine parasite sensitivity/resistance to different drugs. To
formulate mathematical models for analyzing long-term quantitative data
on parasites, vectors, reservoir hosts and human patients.
In order to attain these goals, thorough
investigations of the ecology and epidemiology of Kala-Azar will tease
apart the transmission cycle of the disease in Ethiopian foci.
Long-term studies will quantify the relative contribution of different drivers
of transmission (ecological, epidemiological and anthropogenic
factors) to the overall impact of the disease on human populations.
Sand flies are collected using a variety
of techniques in order to determine the transmission seasons and the
timing of peak sand fly activity. Additional questions to be addressed
include: Where are the sand flies coming from and from how far away?
What are their preferred blood sources (humans, cows, dogs, other)?
What are the main larval breeding habitats? Are they found in any
particular soil types (vertisol)? Is sand fly breeding restricted to
forest and woodland? Are they affected by agricultural soil management
practices (sesame or sorghum)? Is there correlation with organic matter
content and other soil characteristics such as mechanical and
mineralogical composition, redox potential and ratios of exchangeable
cations? Do physical features suchasaggregate stability, deep cracks,
water content, play a role?
What are the significant parasite
reservoirs for infection of sand flies - human or animal? What are the
human populations comprising the significant reservoirs of the disease
(VL/ PKDL patients, asymptomatic carriers, VL-HIV coinfected)? Do
animal reservoir hosts contribute significantly to the transmission
cycles and if so, which species? These questions are being addressed
using diverse field and laboratory techniques. The acquired information
will be thoroughly analyzed using state of the art statistical tools.
Mathematical models will be formulated to assist in experimental design
that will make possible the incrimination of “key” elements
in the transmission cycles, those likely to constitute targets for
future control campaigns.