Biology Reference
In-Depth Information
(B)
(A)
8
3.5
3
6
2.5
4
2
2
1.5
1
0
0
0.5
1
0
0.5
1
Fraction of worms exposed to
treatment
Fraction of worms exposed to
treatment
(C)
0.5
0.4
0.3
0.2
0.1
0
0
0.5
1
Fraction of worms exposed to
treatment
FIGURE 9.10
The influence of treatment coverage, g, in a yearly treatment campaign on
(A) the reproductive number, (B) the equilibrium mean worm load in the population, and
(C) equilibrium prevalence of infection. For a simulation in which k
¼
0.15, R
0
¼
3 (solid
line) and R
0
¼
2 (dashed line).
simulation studies are need to further explore this issue, combining
economic costs with impacts on transmission (i.e. the effective reproduc-
tive number).
Current practice is largely focused on school-age targeting, based on
the ease of access to school children, and increasingly as more drug
donations are made, on community-wide treatment. The age distribution
of the human population where the parasites are endemic is often of
importance in predicting the impact of community-based or school-aged
children-based treatment programs.
42
The explicit representation of this
distribution in transmission dynamic models is therefore highly desir-
able. A simple illustration of this point is provided by calculations of the
fraction of worms treated by a school-age (5
14 years of age) targeted
program. This fraction F is related to the age-specific death rate of
humans, l(a), which defines the age distribution, the age intensity of
infection profile, M(a), and the fraction of children in the population who
e
