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Malaria
Causes,
Symptoms & Treatment
By Cari Nierenberg - Live
Science Contributor
Malaria is a disease
caused by a parasite that gets passed into the bloodstream of humans by the
bite of an infected mosquito.
People with malaria
typically get very sick and experience a high fever, teeth-rattling chills and
muscle aches. If caught early and treated, severe illness and death can usually
be prevented.
Malaria is very rare
in the United States, where about 1,700 cases and five deaths occur each year,
mostly in immigrants and travelers returning from countries where the disease
is common, according to the Centers for Disease Control and
Prevention (CDC).
However, in many
developing countries, malaria is a leading cause of death and disease, where
children under age 5 and pregnant women are the hardest hit groups.
In 2017, there were
219 million cases of malaria worldwide and about 435,000 deaths, according to
the World Health Organization (WHO). The majority of cases were in tropical and
subtropical countries.
Common malaria
regions include large areas of Africa south of the Sahara desert, Southeast Asia, Central and South
America, Haiti and the Dominican Republic, Eastern Europe and the South
Pacific, according to the American Academy of Family Physicians.
It's difficult to
control malaria worldwide because parasites tend to stay in our bodies, and
the immune system is
not very effective at clearing them, said Dr. Edward Ryan, director of global
infectious diseases at Massachusetts General Hospital in Boston.
In addition, some
species of Anopheles mosquitoes are hard
to wipe out, he said.
By 1949, the U.S.
eliminated malaria, according to the CDC.
The country implemented a coordinated public health effort in southern states
that involved spraying insecticides and removing mosquito breeding sites, Ryan
said.
The growing,
widespread use of air conditioning and screens on doors and windows also helped
keep mosquitoes outside of homes, he said.
How do you get malaria?
Malaria is
transmitted by the bite of an infected Anopheles female
mosquito, which passes on the Plasmodium parasite
to people.
Anopheles mosquitoes
thrive in areas with warm temperatures, humid conditions and high rainfall,
according to the University Corporation for
Atmospheric Research in Boulder, Colorado.
Five species of Plasmodium parasites can infect people with
malaria, but some species cause more serious problems than others.
The Plasmodium falciparum parasite is the one most
likely to cause severe, life-threatening illness if the infection is not
promptly treated.
When the malaria
parasite enters a person's body, it travels to the liver, where it multiplies and matures. Parasites are
then released into the bloodstream, where they invade and infect red blood
cells.
The parasites
continue multiplying and infecting other red blood cells, and these cells
eventually rupture and release toxins, causing a person to experience flu-like
symptoms. As the disease progresses, the liver and spleen (which filters and stores blood) can
enlarge.
With severe malaria,
the blood inside the body sludges, or piles up and sticks to blood vessel
walls, so it doesn't flow normally, Ryan told Live Science.
A person may die of
the disease because the sludging blocks blood vessels to organs, such as
the lungs, brain or kidneys, causing damage, he said.
Malaria is not spread
from person to person. But in very rare instances, it can be transmitted by a
blood transfusion containing the parasite, by the sharing of drug needles or
from an infected mother to her baby during pregnancy or delivery.
Two groups most
vulnerable to malaria are young children, who have not yet developed immunity
to the disease; and pregnant women, whose immunity has decreased because they
are expecting, according to the CDC.
Other high-risk
groups are visitors from countries with no malaria and therefore, no immunity,
as well as travelers who grew up in malaria regions, but moved away for long
periods of time and lost their partial immunity to the parasite.
Symptoms
Symptoms of malaria
may develop a week or two after a person is bitten by an infected mosquito, or
they may show up several months or more after exposure, according to the National Organization for Rare Diseases.
Early symptoms may
resemble the flu, such as fever,
chills, headache and muscle aches, Ryan said.
Other early signs
include tiredness, nausea and vomiting. Then, a person may experience a high
fever and teeth-rattling chills, followed by heavy sweating and exhaustion when
the fever breaks.
Malaria can rapidly
become a serious, life-threatening disease. According to the CDC, some
complications of severe malaria, which is more common with P. falciparum infections, may include:
· Liver
and kidney failure
· Mental
confusion, convulsions and coma
· Severe
anemia from destruction of red blood cells
· Jaundice
(yellowing skin and eyes) from a loss of red blood cells
· Death
Diagnosis and treatment
A simple blood test
is used to detect the malaria parasite under a microscope, Ryan said. The blood
test confirms malaria parasites are present and identifies the species causing
illness.
If the illness is
diagnosed early and treated, it's totally curable and all malaria parasites can
be cleared from the body, he said. Both intravenous and oral medicines are
available to treat malaria and remove the parasite from the blood.
The majority of
people with malaria in the U.S. are hospitalized, but the length of stay
depends on which species of the parasite an individual has been infected with
and how healthy someone was to start, Ryan said.
A patient will
receive anti-malarial medications to fight the parasite and will be monitored
to ensure the level of infection is falling.
Some malaria drugs
may not be effective because parasites have become increasingly resistant to
them, making it difficult to control the disease worldwide, the CDC reports.
Prevention
When visiting
malaria-zone countries, travelers need to consider the time they will spend in
each destination, the type of travel (air-conditioned hotels versus rural
villages) and the season (some locations have year-round malaria risk, while
others have high and low periods), Ryan said.
Minimize risk by
taking the following precautions:
· Take appropriate anti-malarial medications — before,
during and after the visit — which are highly effective at preventing the
disease, Ryan said.
· Apply insect repellent. Choose products containing DEET when
applying the repellent on exposed skin. Spray pyrethrin, an insecticide, on
clothing.
· Limit outdoor activities between dusk and dawn — the peak
feeding times for Anopheles mosquitoes. Wear
long-sleeved shirts and pants to cover skin.
· Use bed netting. If visiting rural villages, sleep under
insecticide-treated bed netting and spray insecticides indoors to keep mosquitoes
away.
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