Biology Reference
In-Depth Information
dramatic economic development that saw large-scale social infrastructure
projects, including water and sewage systems, which undoubtedly facil-
itated reductions in the prevalence of infection (
Figure 13.2
B).
Today, A. lumbricoides has been almost completely eliminated from
South Korea as well as Japan and Taiwan.
25
e
27
The prevalence of
A. lumbricoides is also rapidly decreasing in China,
29
especially in urban
areas where urbanization has been accompanied by improvements in
water and sanitation. Globally, country level analysis suggests that the
prevalence of A. lumbricoides is negligible in those countries with a gross
domestic product
US$20,000 in 2010.
19
Since 2000, a number of other countries have implemented large-
scale campaigns using anthelmintic drugs, including albendazole or
mebendazole, through either school-based de-worming programs or
community-based lymphatic filariasis elimination, and such campaigns
will, no doubt, contribute to lower levels of infection in the future (see
Chapter 15).
>
GLOBA
L NUMBERS AT RISK AND INFE
CTED
Possibly the first global estimates of A. lumbricoides were provided by
Normal Stoll in his seminal This Wormy World study.
20
He suggested that
0.644 billion people out of a global 1947 population of the 2.167 billion
were infected with A. lumbricoides, which was equivalent to 30% of the
world's population. Some 40 years later, David Crompton
17
estimated
a global prevalence of 22%, including some 1.008 billion people in 1988, an
estimate derived independently from previous estimates and without
extrapolation from Stoll's values. Subsequently, Don Bundy and
colleagues estimated the total number of A. lumbricoides infection to be
1.382 billion in 1990, representing 34% of the world's population.
15
Inevitably, the number of prevalence studies included in these different
estimates varies, hence the reliability of estimates at global and country
levels also varies.
Based on the global limits of transmission (
Figure 13.1
A), Pullan and
Brooker
19
estimated that 5.23 billion people (0.99 billion of school-going
age) were living in areas of stable A. lumbricoides transmission world-
wide in 2010, and hence at risk of infection. The vast majority (71%) of
these individuals were living in Asia and Oceania, with only 18% living in
Africa and the Middle East, and 11% in Latin America and the Caribbean
(LAC) (
Table 13.1
and
Figure 13.1
A).
Being at risk of infection is not the same as being infected, however.
Using data from the Global Atlas of Helminth Infection,
30
e
32
Table 13.2
provides estimates of the global number individuals infected with
A. lumbricoides in 2010, by region. These estimates are derived through
