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Malaria

Malaria
Definition
Malaria is an infectious disease caused by a parasite that spends part of its
life cycle in humans and part in mosquitoes.


Description
Malaria is a potentially fatal disease that has infected humans as far back
as 50,000
Egypt in 2700
from the same period describe the symptoms of the disease. The English
name of the disease comes from an eighteenth-century Italian doctor
who wrote a textbook about it and attributed it to bad air, or
BCE. There are records of mosquito netting being used inBCE to protect against malaria. Chinese medical recordsmalaria
in Italian.
Humans develop malaria when they are infected with a protozoan
called
the bloodstream and are carried to the liver, where they infect liver cells
and multiply. The mature parasites are released back into the bloodstream,
where they infect red blood cells. The red cells burst in two to
three days, releasing more parasites that, in turn, invade more red blood
cells. Most of the symptoms of malaria (fever,
chills, generally sick or flu-like feeling) are
related to the destruction of red blood cells. The
reason why the fever associated with malaria
comes in two- or three-day cycles in some people
is that the bursting of infected red blood cells
and the infection of new red blood cells occurs
every two to three days.


There are four different species of
Plasmodium
that infect people. One of these,
falciparum
other three. It can cause failure of the lungs, kidneys, and central nervous
system within a few hours or days. The different species also take different
lengths of time to produce the first symptoms of malaria in
humans. Some remain in the liver for long periods of time, thus causing
flare-ups of the disease months or even years later. These variations are
one reason why doctors try to identify the particular
when they test a person
be infected with more than one species of the parasite at the same time.
People cannot get malaria from sharing a household with an infected
person since it takes more than a week before a mosquito is able to
transmit the disease. It is possible for a pregnant woman to transmit the
disease to her unborn baby, however. It is also possible to get malaria
through a transfusion of infected blood, but this form of transmission
is rare in developed countries. In the United States, people who have traveled
in an area with endemic malaria cannot donate blood for a full year
after returning to the United States. They are forbidden to donate blood
for three years if they have been treated for malaria.
Plasmodium, is much deadlier than thePlasmodium speciess blood for malaria. It is possible for a person to
Demographics
Malaria is one of the most common infectious diseases in tropical and
subtropical parts of the world. These countries account for 41 percent
of the world
900 million cases of malaria around the world each year and 1 million to
3 million deaths, most of them African children under age five. In some
parts of Africa, it is estimated that one person dies of malaria every thirty
seconds. The disease is endemic in parts of Africa, southern Asia, and
portions of South America.
Malaria has not been endemic in the United States since 1951, when
a four-year program was started in 1947 to spray areas in the southeastern
part of the country that were known to harbor the mosquitoes
that transmit malaria. By 1952 the Centers for Disease Control and Prevention
(CDC) reported that malaria had been eradicated from the
United States. Cases of malaria since that time were either acquired by
people traveling to countries where malaria is endemic or were small local
outbreaks caused by local mosquitoes biting infected travelers and then
transmitting the malaria parasites to others nearby. In 2002 the CDC
reported 1,337 cases of malaria in the United States, including eight
deaths. All but five cases were acquired abroad.
People who are at greatest risk for malaria are those who have never
been exposed to the disease, pregnant women, and young children. Some
researchers also think that genetic factors may increase some people
of getting the disease.
s risk
Causes and Symptoms
The cause of malaria is a protozoan of the genus
deadly of the four species that can cause malaria in humans is
falciparum
of chills and shaking followed by fever and sweating lasting four to six
hours. People infected by
as well. In some cases, the early symptoms of malaria may be mistaken
for the flu.
Children infected by
on the brain and suffer permanent brain damage even if they survive.
Adults infected by
dehydration, an enlarged liver and spleen, rupture of the spleen, severe
headache, loss of blood supply to the brain, and coma. Some die. The
destruction of red blood cells by the parasite may cause the urine to look
brown or black, which is why the disease got the name
fever.
Plasmodium. The mostPlasmodium. The classical symptom of malaria is a repeated cycleP. falciparum may feel a tingling in the skinP. falciparum may develop increased fluid pressureP. falciparum may develop kidney failure,blackwater


Diagnosis
Diagnosis of malaria is based on a combination of the patient
and the results of blood tests. The patient
the dates of any trips abroad, because two of the four species of
the malaria parasite can remain dormant in the liver for months or
even years.
The basic blood test involves looking at blood smears made by
pricking the patient
technique is called a thick smear, which is used to estimate the number of
parasites in the blood. The other is called a thin smear and is used to
determine the species. A rapid test called OptiMAL has been developed
to distinguish
time than the smear method and can be used by doctors in areas without
hospital laboratories.
s finger at twelve- to twenty-four-hour intervals. OneP. falciparum from the other species. It gives results in less
Treatment
Malaria is treated with various combinations of drugs, which may be
given by mouth or intravenously. Patients infected by
be taken to a hospital for treatment because of the possibility of major
organ damage. The oldest drugs used to prevent or treat malaria are quinine
and chloroquine. Relatively inexpensive, they are not always effective
because the malaria parasites have developed resistance to them in
some countries. Newer drugs have been developed that are more effective
for resistant strains. People who are traveling to parts of the world where
malaria is endemic need to take these drugs while they are abroad.
The specific drug that is given to a patient and the length of treatment
depend on the type of malaria, the source of the infection, the
patient
People often feel weak and tired for a few weeks when taking these
medications.
P. falciparum mays age, and the severity of the symptoms when treatment began.
Prognosis
Malaria caused by
of the first symptoms. In some areas, the death rate from this type of
malaria is as high as 20 percent. People infected by the other three species
of
months until all the parasites have been cleared from their livers.
P. falciparum is the most deadly; it can kill within daysPlasmodium usually recover, but some may have bouts of malaria for
Prevention
There is no vaccine effective against the malaria parasite, although scientists
are working on several possibilities. For the time being, prevention is
the most effective way to lower one
three basic strategies recommended by the CDC:
s risk of getting malaria. There are
draining swampy areas. This approach is called vector control.
Controlling the mosquito population by using insecticides and
other sleeping areas. These nets have cut the number of deaths
from malaria in parts of Africa by 20 percent.
Using mosquito netting treated with insecticide to cover beds and
where malaria is endemic. The CDC has general advice for travelers
and a list of countries where travelers are at risk for malaria at
http://www.cdc.gov/malaria/travel/index.htm.
Taking medications to prevent the disease when visiting countries
The Future
It is unlikely that the mosquitoes that carry malaria will ever be completely
wiped out. At present, efforts to relieve the impact of malaria in Africa
are aimed at preventing the disease. Methods include spraying insecticides,
providing people with insecticide-treated mosquito netting, and
supplying poor countries with antimalarial drugs. In 2005 the President
Malaria Initiative (PMI)
the National Institutes of Health, the World Health Organization, and
the World Bank as well as the White House
to cut deaths from malaria by 50 percent in fifteen African countries.
The most promising area of malaria research as of 2008 was the development
of vaccines against the disease. Scientists have identified the
genetic sequence of the malaria parasite, which may help researchers target
a particular stage in the life cycle of the parasite or prevent it from developing
inside the mosquito. One possibility is developing a vaccine that
would stop the parasite inside the human body before it gets to the point
of infecting the red blood cells. Another group of researchers is experimenting
with cultivating
parasite with radiation in order to make a vaccine. This approach is
described in the video listed below.
sa cooperative program that involves the CDC,began a five-year programP. falciparum inside mosquitoes and treating the
SEE ALSO
Influenza; Syphilis; West Nile virus infection
For more information
BOOKS
Abramovitz, Melissa. Malaria. Detroit, MI: Lucent Books, 2006.
Lynette, Rachel.
Marcus, Bernard A.
Malaria. Farmington Hills, MI: KidHaven Press, 2006.Malaria. Philadelphia: Chelsea House Publishers, 2004.
PERIODICALS
Appleton, Samantha.
2005. Available online at http://www.newyorker.com/archive/2005/10/24/
slideshow_051024?slide=1#showHeader (accessed April 24, 2008). This is a
slide show of fifteen photographs of the 2005 malaria epidemic in Africa.
McNeil, Donald G., Jr.
December 11, 2007. Video available online at http://video.on.nytimes.com/
index.jsp?fr_story=6e4647e2867283dce5b8cb2cf46003e7fdcd6267
(accessed April 25, 2008). This is a four-minute video about ongoing efforts
to develop a vaccine against malaria.
Slide Show: Healing Africa.New Yorker, October 24,Searching for a Cure for Malaria.New York Times,
WEB SITES
Centers for Disease Control and Prevention (CDC).
Available online at http://www.cdc.gov/malaria/ (updated April 18, 2008;
accessed April 24, 2008). Contains links to news items as well as basic
information about malaria and its treatment.
Mayo Clinic.
malaria/DS00475 (updated February 8, 2008; accessed April 25, 2008).
President
fightingmalaria.gov/resources/pmi_fastfacts.pdf (posted January 2008;
accessed April 26, 2008).
Sumanas, Inc.
online at http://www.sumanasinc.com/scienceinfocus/sif_malaria.html
(accessed April 5, 2008). This is an animation of the life cycle of the malaria
parasite with voiceover. It takes three minutes to play.
WGBH Educational Foundation.
www.pbs.org/wgbh/rxforsurvival/series/diseases/malaria.html (posted 2005;
accessed April 24, 2008). The right-hand side of the page includes links to
three videos on malaria, each about five minutes in length.

WORDS TO KNOW
Dementia: Loss of memory and other mental
functions related to thinking or problem-solving.
Endemic: A term applied to a disease that
maintains itself in a particular area without
reinforcement from outside sources of infection.
Protozoan (plural, protozoa): A one-celled animallike
organism with a central nucleus enclosed by
a membrane. Many protozoa are parasites that
can cause disease in humans.
Spleen: An organ located behind the stomach that
cleans old blood cells out of the blood and holds
a reserve of red blood cells.
Vector: An insect or other animal that carries a
disease from one host to another.

Malaria Research and the Nobel Prize
One indication of the importance
complexity
prizes in medicine that have been awarded to
doctors who studied the disease. Charles Louis
Alphonse Laveran (1845
doctor working in a military hospital in Algeria in
1880 when he discovered that malaria is caused by
a protozoan (a type of one-celled organism). This
was the first time that a protozoan had been
shown to cause any disease in humans. Laveran
was awarded the Nobel Prize in Physiology or
Medicine in 1907.
In 1898, Sir Ronald Ross (1857
doctor working in India, was able to show that
mosquitoes are the vectors that carry malaria to
humans. Ross even demonstrated that the parasites
are present in the mosquito
He was awarded the Nobel Prize in Physiology or
Medicine in 1902. Austrian doctor Julius Wagner-
Jauregg (1857
He showed that malaria could actually be used to
treat patients suffering from late-stage syphilis, a
common cause of dementia in the early twentieth
century. The reason this treatment was thought to
work was that the fever caused by the malaria
parasite was high enough to kill the bacteria that
cause syphilis.
The fourth Nobel Prize in Physiology or Medicine
related to malaria research was given in 1948 to
Paul Hermann Müller (1899
chemist who discovered dichloro-diphenyltrichloroethane
(DDT) in 1939. DDT was the first
insecticide that was effective in controlling the
mosquitoes that spread malaria.
and theof malaria is the number of Nobel1922) was a French1932), a Britishs salivary glands.1940) won a Nobel prize in 1927.1965), a Swiss

Malaria: Topic Home.Malaria. Available online at http://www.mayoclinic.com/health/s Malaria Initiative (PMI). Fast Facts. Available online at http://www.Malaria: Cooperation among Parasite, Vector, and Host. AvailableRx for Survival: Malaria. Available at http://
s historys history is critical, particularly
s population. It is estimated that there are between 400 and
Plasmodium through the bite of a mosquito. The parasites enter

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