Biology Reference
In-Depth Information
Greenwood, 2008b
). The first task of a malaria control program is to stop
deaths due to malaria, which necessarily means an emphasis on falciparum
malaria at the onset (
Tatem et al., 2010
). However, as has been repeatedly
shown in earlier chapters in this issue, vivax causes mortality and substantial
morbidity across the world (
Genton et al., 2008
;
Oh et al., 2001
). Impor-
tantly, vivax malaria has several attributes that make it difficult to control
and very difficult to eliminate. Once modest success has been achieved in
malaria control, especially in countries outside of Africa, vivax and other
forms of relapsing malaria (e.g.
Plasmodium ovale
) will increasingly become
important until malaria control is primarily if not exclusively focused on
vivax malaria (
Rajakaruna et al., 2010
;
Aguas et al., 2008
). In some parts of
Asia and Latin America, this has already occurred. In sub-Saharan Africa,
malaria control will, for the foreseeable future, be concerned primarily with
falciparum malaria, however, substantial populations of relapsing malaria
exist in Africa despite their clinical invisibility to most physicians and will
become increasingly important as established forms of malaria control using
rapid diagnosis and treatment as well as insecticide-treated bed nets (ITN)
continue to lower the disease impact of all forms of malaria.
1.1. Geographic Range and Temperature Tolerance
Vivax malaria has a broader geographic range and temperature tolerance
than falciparum malaria. The classic success stories from the 1950s-1960s
Global Malaria Eradication Program (GMEP) were largely in areas of sea-
sonal malaria transmission away from the equator, which are the regions
inhabited by vivax malaria (
Bruce-Chwatt, 1977
;
Colbourne, 1962
). The
historical distribution of malaria transmission, originally mapped by Lysenko
[EDITOR = SEE REFS in CHPT 1; VOL 80], has been digitised by the
Malaria Atlas Project (MAP). (Chapter 1, Figure 1.3). In nearly half the
countries of the world shown on the map, malaria has been eliminated over
the twentieth century, which has considerably shrunk today's distribution of
vivax malaria (see chapter 1, volume 80, and Gething et al., 2012). However,
about 100 countries, both tropical and sub-tropical, currently have some
degree of malaria transmission (
Tatem et al., 2010
). Although often regarded
as due to exceptional circumstances, vivax malaria has been transmitted dur-
ing the summer months in sub-Arctic regions of the Northern hemisphere.
The most important single determinant of malaria transmission in such cold
climates is the amount of time when the temperatures remain above a mean
of 18 °C (
Gething et al., 2010
), as described in chapter 1 of this volume.
Besides seasonality, temperatures also vary by altitude which can produce
