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Malaria is among the leading infectious
causes of morbidity and mortality in children worldwide. Each year,
there are 300 to 500 million clinical cases, causing between 1.5
and 2.7 million deaths, most in sub-Saharan African children under
the age of 5 years. Increasing drug resistance, climatic changes,
population shifts, economic changes, abandonment of malaria control
programs, and insecticide resistance all contributed to a resurgence
of malaria in the developing world from the 1970s to the 2000s. Recent
World Health Organization, governmental, and nonprofit foundation
support for effective preventative measures—such as insecticide-treated bednets,
indoor residual spraying, and the implementation of artemisinin combination
therapy as first-line treatment for malaria in many sub-Saharan
African countries—appears to have significantly reduced
malaria incidence and deaths in some countries.1
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More than 40% of the world’s population, or
2.5 billion people, are at risk for malaria in 90 countries in Africa,
Asia, South and Central America, and Oceania (Fig.
352-1). For many years, it appeared that malaria in humans
was caused by four species of Plasmodium: P
falciparum, P vivax, P ovale, and P malariae.
There is now evidence that P knowlesi, a Plasmodium species
that usually infects monkeys, has crossed over to cause malaria
in humans in Southeast Asia, notably in Malaysia4;
it is now considered a fifth human malaria species. Plasmodium
falciparum is found mainly in tropical areas, where warm
weather ensures the relatively constant presence of the Anopheles vector. Plasmodium
vivax has the widest geographic distribution of the four
species and is found in both tropical and temperate areas. Plasmodium
ovale is found primarily in sub-Saharan West Africa, where
it appears to have almost completely replaced Plasmodium
vivax. Plasmodium malariae can be seen
in both tropical and temperate zones but is the least common of
the malaria species.
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Diagnostic and treatment approaches differ significantly in malaria
endemic countries as compared to countries like the United States, where
almost all malaria is imported. In the United States, all of the
approximately 1500 cases of malaria that were reported to the Centers
for Disease Control and Prevention (CDC) in 2005 occurred in travelers
to or immigrants from malaria-endemic countries, with the exception
of two cases of congenital malaria, in which the mothers were immigrants
from malaria-endemic countries.2 Rare cases of local transmission have
been reported in the United States.3
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Malaria can be a life-threatening illness. Delay in seeking treatment,
misdiagnosis, or both are often seen in individuals who die from
malaria in the United States.2 Any febrile child who has
been in a malaria-endemic area in the preceding year should be assessed
for this illness.
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Organisms and
Life Cycle
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Plasmodium species can infect many different animals
but most are host-specific. P falciparum is ...