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86 CHAPTER 4

Source: Centers for Disease Control and Prevention (CDC)

FIGURE 4-6 Parasite life cycle of the genus Plasmodium

there is another phase of multiplication that results in the as this is the most active feeding times for mosquitoes.
production of sporozoites that reach the salivary glands The mosquito is infected by biting a patient infected
to be injected into a new host. The parasites in the blood with malaria, where it aspirates the sexual forms of the
were first seen in 1880 by French army surgeon Alphonse parasite, the gametocytes, along with the victim’s blood.
Laveran, who was looking for a bacterial cause of malaria. These gametocytes continue the sexual phase of the
He immediately realized that parasites rather than bacte- cycle and the sporozoites fill the salivary glands of the in-
ria were responsible for the disease (Cox, 2002). fested mosquito. Once the mosquito becomes infected, it
is destined to remain so for life.
Disease Transmission
Laboratory Diagnosis
The female Anopheles mosquito is the chief vector and
the most common means for transmitting malaria to Thick and thin peripheral blood smears stained with
humans. Some 60 species of this mosquito have been Giemsa or Wright-Giemsa stain are the methods of
identified as vectors for malaria and the vector for a given choice for diagnosing infections with a Plasmodium
geographic region will vary. The infection is transmitted species. The diagnosis can only be definitely confirmed
by the bite of an infected female Anopheles mosquito. by the presence of the organism as an intracellular in-
The mosquito most frequently bites at dawn and at dusk, clusion of the RBCs. Careful timing of the collection of