Malaria:: An Update for Physicians

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Introduction and Historical perspective

Malaria is caused by infection with protozoan parasites of the Plasmodium genus, transmitted to humans by female anopheline mosquitoes. Plasmodia have adapted to a wide variety of vertebrate hosts ranging from reptiles to mammals, although with 1 notable exception, human malaria is not a zoonosis. Infections likely to represent malaria have been described since mankind began to record its experiences. The earliest accurate description of human malaria in European literature has been attributed

Epidemiology

The current distribution of malaria covers the tropics and large parts of the subtropics (Fig. 1). World Health Organization (WHO) estimates of malaria deaths worldwide decreased from 1 million in 2000 to more than 700,000 in 2009, with an estimated 756 million people at risk of the disease.2 In line with these WHO data, largely derived from data supplied by National Malaria Control Programs, a summary of recent peer-reviewed publications also points to substantial reductions in malaria cases

Pathogenesis

The primary route of infection for all plasmodia infections is through the bite of a female anopheline mosquito. Less common routes of infection include blood transfusion of parasitized erythrocytes and congenital transmission. Following the bite of an infected mosquito, plasmodia sporozoites enter the subcutaneous tissue of the skin and migrate to local capillaries and lymphatics before passing to the liver, where they invade hepatocytes and develop into merozoites via a process of asexual

Clinical features

In European and North America, more than 95% of malaria infections occur in travelers, often within the first month of return.25 Delay in developing illness has been associated with the use of appropriate antimalarial prophylaxis, and clinicians seeing returning travelers should be aware of this possibility.26 Presentation is nonspecific and may mimic other diseases including influenza, septicemia, gastroenteritis, and viral syndromes. A high index of suspicion is required, usually triggered by

Diagnosis

Once malaria is suspected, it is usually straightforward to diagnose. Commonly used diagnostics include thick and thin Giemsa-stained blood smears and immunochromatographic rapid diagnostic tests (RDTs) of malaria antigens, both of which are in widespread use.41, 42 In expert centers, light microscopy can detect as few as 50 parasites/μL (approx 0.001%), increasing to around 500/μL in routine settings. Sensitivity for RDTs decreases with parasitemias less than 100/μL for P falciparum, with

Management

The management of malaria depends on the species involved. If there is doubt or difficulty identifying the infecting species, management should be as for P falciparum infection while clarification as to the infecting organism is sought (a separate thick and thin blood slide should be sent to the local reference laboratory, ideally accompanied by ethylenediamine tetraacetic acid (EDTA) blood in case PCR is required). In all cases, management should be undertaken in conjunction with a physician

Early diagnosis

Many malaria deaths in travelers result from a delay in diagnosis of malaria. The reasons for the delay are multifactorial. Education on preventing delay in seeking medical help for malaria must be provided at the pretravel consultation. Preventing delays in recognizing and testing for malaria at the first medical contact requires educating physicians and other health professionals on appreciating the symptoms and signs of malaria.

Malaria and pregnancy

In highly endemic areas where immunity to severe disease is acquired in childhood, malaria may account for up to one-half of all low birth weight babies and one-quarter of severe maternal anemia.79 In this context, severe disease is confined largely to primigravidas, and pregnant women coinfected with HIV. Malaria in the multigravida pregnancy can present insidiously with little sign of the infection other than anemia and fetal growth retardation. In contrast, all pregnant women from nonendemic

Summary

Despite efforts to control malaria, it continues to claim the lives of more than 2000 people every day and remains the most important human parasitic disease. The development of artemisinin combination therapies for nonsevere malaria and parenteral artesunate for severe malaria represent the most important advances in antimalarial therapeutics. Progress in reducing global mortality depends on ensuring that such treatments reach those most in need. These drugs also offer the clearest therapeutic

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    BN has no conflicts of interest to declare. RHB received funds from Sigma-Tau for contributing to their advisory board.

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