Worldwide there are 300 to 500 million cases of clinical malaria every year, and 3,000 children die from the disease each day. Of the one million people who die from malaria every year, most of them are children less than five years old who reside in sub-Saharan Africa.
Transmission of Disease
The disease transmits to humans via the female Anopheles mosquito which bites a human who already carries the malaria parasite. After she obtains a blood meal, the mosquito acquires the parasite and then transmits it to another human via a bite. The parasite has several species, all of which may cause a life-threatening illness, but falciparum malaria is without doubt the most deadly.
The disease does not spread by casual contact with another human, and it is not a sexually transmitted disease. Though not common, malaria can transmit through blood transfusion, organ transplant, or shared needles or syringes which contain blood with the malaria parasite. Women can transmit it to their child during pregnancy or labor and delivery, and this is particularly an issue when the parasites invade the mother’s placenta.
An even more ominous scenario is that of a woman with human immunodeficiency virus infection and who carries the malaria parasite during pregnancy. The two diseases together worsen the clinical course of each other and increase the likelihood that the mother will transmit one or both of them to the child.
Epidemiologists describe a disease as endemic when there are enough cases in a geographic region such that the medical condition is continuously present there. Prior to 1951, malaria was endemic in the United States, where it caused much sickness and death. Today there are approximately 1,500 cases of it each year in the United States, and few physicians there encounter a case of it.
Malaria remains endemic in sub-Saharan Africa and Asia, and most deaths from the disease occur in those geographic regions. Nearly half of the world’s population today is at risk for the acquisition of this disease because the female Anopheles mosquito is everywhere on the planet but Antarctica.
Though virtual elimination of malaria has taken place in the United States, the threat of its return is still present because of travelers between the United States and malaria endemic countries who may acquire or carry the parasite. Malaria tends to occur in poor tropical and subtropical regions of the world.
Although anyone can acquire malaria, the disease is a particularly serious risk for small children less than five years old and pregnant women. This is because the immune systems of small children have not yet adequately developed, and the immunity for pregnant women tends to be somewhat compromised.
Malaria is one of the world’s three greatest public health problems; the other two are tuberculosis and human immunodeficiency virus infection. Medication to treat and cure malaria has been available for more than half a century, but there is still no satisfactory solution to the problem. This has to do with lack of availability of medication, laboratory staff, and diagnostic medical equipment in some poor countries.
The best diagnostic tool for malaria, aside from the clinical history and physical examination, is a microscopic smear of the patient’s peripheral blood.
Resistance to several of the antimalarial drugs continues to grow. It has to do with mutations of the malaria parasite such that the drug will no longer kill it or cure the infection. There is also an issue with fake or counterfeit drugs to treat malaria, and thousands of people who have taken these agents have died from inadequate treatment of the disease.
Prevention
To prevent the acquisition of malaria, insecticide-treated bednets are useful as they contain chemicals which repel or kill the mosquito while the individual sleeps under them at night. Indoor residual spraying of walls and surfaces of homes with insecticides in malaria endemic regions will also reduce the transmission of disease.
Women who are pregnant and who do not reside in malaria endemic areas of the world should not travel to those regions, but intermittent doses of antimalarial medication for pregnant women are beneficial in prevention of the disease in these patients. People who travel to areas where malaria is present should take medication to prevent disease acquisition before they depart.
Since mosquitoes bite between dusk and dawn, it is important to avoid them during those times. People in these areas should wear long pants, long-sleeved shirts, and light-colored clothes, and they should spray themselves with insect repellents. Moreover, the use of screens in houses may keep mosquitoes outside.
References
Centers for Disease Control. (2010). Malaria. Retrieved December 5, 2010.
Ivo Mueller, Mary Galinski, J. Baird, et al, “Key gaps in the knowledge of Plasmodium vivax, a neglected human malaria parasite.” The Lancet Infectious Diseases 9 (2009): 555-566.
Michael Koger - Dr. Koger obtained his medical education at Meharry Medical College and specialized in Internal Medicine.
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