This thesis describes a comprehensive cohort study of
cutaneous
leishmaniasis
(CL) in a population of 2,704 followed over a period
of
19
months,
in the
Opon focus,
Landazury, Santander, Colombia. Chapter 1
reviews
the
public
health importance
of
CL at international, national (Colombia), and
local
(Santander) levels.
Particular
attention is given to the distribution of
Leishmania
parasites,
sandfly vectors
and
reservoirs in Central and South America, according
to the
ecological regions
defined
by the Andes mountain range. Chapter 2
describes the
materials and methods of the
whole project, emphasising its clinical, epidemiological
and entomological
aspects,
respectively. Each one of the following three
chapters contains
an
introduction,
results and discussion. Chapter 3
addresses
the
diagnosis,
aetiology
and clinical
symptoms of leishmaniasis patients.
The
principal
findings
were
as
follows:
(i) from
three methods tested, PCR and the
direct
examination
of slides are recommended as
diagnostic tools in distant leishmaniasis foci; (ii) the
main
parasite
circulating
in
Opon
is L. panamensis; (iii) cutaneous lesions were
larger if
patients
were
infected
at
a
younger age, and tended to be located on the face
of children, on the legs
of
women,
and on the torso of man; and (iv) about
10.2%
of
CL
patients
had
mucosal
lesions
of
low severity. Chapter 4 presents the results of the
cross-sectional
survey
carried
out
between May-July 1995, and the results
of the
19
months prospective
survey. Results are divided into sections on the
population
structure; the
population
transmission rate for infection and
disease; the
personal,
household
and
village
risk
factors for infection; seasonal variation
in the incidence
of
leishmaniasis; the
risk
factors for developing clinical symptoms with
infection;
acquired
immunity;
and
finally an analysis of the potential
bias in the
study.
The
main
findings
were
as
follows: (i) the cumulative prevalence of
infection
amongst the
whole study
population was 0.75; (ii) the average transmission
rate
in this focus is
currently
ca.
0.19/year; (iii) the risk of infection is equal
for
both
genders
and
for
all ages;
and
(iv)
transmission was less likely in houses surrounded
by
secondary
forest.
In Chapter
5
the sandfly fauna in the focus are described, focusing
on their
seasonal
and
nocturnal
activity patterns; the relationship between habitat type
and
indoor
sandfly
abundance;
the spatial relationship between abundance
and transmission
rate; and the
natural
infection rate with Leishmania. The main
findings
were
as
follows:
(i) the
principal
vectors in the Opon focus are Lu. trapidoi and
Lu.
gomezi;
(ii)
a significant
proportion
of transmission to humans takes place
indoors
and at night; and
(iii) the
widespread
deforestation that characterises the Opon focus has
not
caused any
reduction
in the
incidence of leishmaniasis, presumably
because the
sandfly vectors
continue to
breed
successfully in the cacao plantations that
have
replaced much
of the
primary
forest.
Chapter 6 provides a discussion of the complete
project,
focusing
on the
significance
for public health in Santander.
