A Textbook of Clinical Pharmacology and Therapeutics

●Malaria 361

●Trypanosomal infection 364

●Helminthic infection 364

CHAPTER 47

47 Malaria and other parasitic infections

PARASITIC INFECTIONS

MALARIA

It estimated that malaria infects 300–500 million humans per
year throughout the world, and up to 2 million (mainly chil-
dren) die annually. Approximately 40% of the world popula-
tion live in malarious areas, particularly in equatorial regions.
Malaria is transmitted to humans in the saliva of the anoph-
eles mosquito and is caused by protozoan organisms of
the genus Plasmodium. There are four major species, namely
P. falciparum,P. vivax,P. ovaleandP. malariae.P. falciparumis
the most lethal form. Malaria is one of the most common
causes of serious illness in the returning traveller. At least
2000 cases are imported into the UK (10 000 in Europe) per
year. Air travel and the incubation period of the disease
have raised the awareness of diagnosing and appropriately
treating malaria even in areas where it is not endemic (e.g.
hospitals near international airports in Western Europe and
the USA).

Visitors to endemic areas must be warned of the infection

risk and advised that prophylactic drug therapy should be

taken, but that it is not 100% effective. They should also be

advised to wear long-sleeved clothing to cover extremities

(especially in the evenings, when mosquitos feed) to use

mosquito-repellent sprays, to sleep in properly screened rooms

with mosquito nets (impregnated with pyrethroids) around the

bed and/or to burn and vapourize synthetic pyrethroids dur-

ing the night. In addition to chemoprophylactic drug therapy,

travellers to remote areas should be advised to carry standby

antimalarial drug treatment with quinine. Where there is doubt

concerning the suitability of drug therapy for malaria prophy-

laxis or treatment, the malaria reference laboratory at the

London School of Hygiene and Tropical Medicine has advice

and guidance (Tel. 020 7636 3924 for health professionals and

Tel. 09065 508908 for the general public, regarding malaria

prophylaxis: website http://www.hpa.org.uk/srmd/malaria).

Figure 47.1 illustrates the Plasmodiumlife cycle and the

therapeutic targets.

Female

anopheline

mosquito

BITE

BITE

Sporozoites
(in salivary gland)

Oocyst

Zygote

Erythrocytic

stages

Schizogony

Microgamete

and

macrogamete

Trophozoites

Microgametocyte

and

macrogametocyte

Gametocidal

(pyrimethamine)

Atovaquone

Artemesinin

Clinical cure

(chloroquine,

quinine,

amodiaquine,

pyrimethamine,

mefloquine,

halofantrine)

Human Drug therapy

Hepatic

Pre-erythrocyte

phase

Merozoites

Schizonts

ve

ve

ve

ve

ve

Suppressive

(quinacrine,

pyrimethamine)

Radical cure

(primaquine)

Figure 47.1:Malaria

life cycle and type of

drug treatment.