mosquito

Malaria: a disease caused by protozoa carried by mosquitos

Dr. Crutchfield, my neighbor recently traveled to Africa and told me he caught malaria when he was there. What is malaria?

Malaria is an infectious disease that is spread by mosquito bites. It
is estimated that over 200 million people contract malaria every year
around the world, and over 500,000 people die every year from the
disease. Most deaths from malaria occur in Africa in children under the
age of five.



The mosquito is the carrier of a parasite that is in the saliva of
the mosquito. When mosquitoes bite humans, they inject a unique
anticoagulant contained in their saliva into the site of the bite so
they can keep drinking blood without the blood clotting. In addition to
the anticoagulant (which stops blood from clotting), the saliva of an
infected mosquito also contains the protozoan parasite that causes
malaria.

Protozoa are single-celled organisms that are larger and more complex
than bacteria. The exact type of protozoan that causes malaria is
called Plasmodium. There are four sub-types of plasmodia that cause
malaria. Plasmodium falciparum causes the most severe forms of malaria
and is responsible for the most deaths caused by malaria.

Malaria played a very significant role in World Wars. In World War
II, over 500,000 American soldiers were infected with malaria. An
estimated 60,000 American soldiers died from the disease, which is more
than the total number of soldiers who died in the entire Vietnam War.

The parasite enters the blood of a human from the infected mosquito
bite. Interestingly, only female mosquitoes transmit malaria. Male
mosquitoes don’t drink blood.

When the parasite infects red blood cells and is released from red
blood cells into the blood, the symptoms of malaria occur. Once the
parasite is in the blood, it travels to the liver, where it lives and
matures. After maturation, the parasites move into the blood and infect
red blood cells. This maturation process usually takes two to several
weeks, but some strains of the parasite can lay dormant in the liver for
up to a year.

At this point, if a person is bitten by an uninfected mosquito, that
mosquito can become a new parasite carrier and infect another uninfected
person, continuing the spread of the disease.

In addition to mosquito bites, malaria can be transmitted from
pregnant mother to fetus, via blood transfusions, and from shared
needles.

Symptoms
The initial symptoms of malaria are very similar to having the flu. They
usually occur about two weeks after the mosquito bite, but in some
cases may not develop for over a year. Malaria symptoms include fever,
chills, nausea, diarrhea, headaches and vomiting. One of the hallmarks
of having malaria is a condition called “paroxysms.”  This is when a
person cycles between shivering chills and sweating fevers.

Sometimes, without treatment, malaria can recur in the same person
several times. In severe cases, malaria can affect the brain, lungs, and
other organs, leading to death.

Prevention
Malaria is prevalent in sub-tropical and tropical areas such as
sub-Saharan Africa, the Subcontinent of Asia, and Central America. If a
person is traveling to a malaria-prone country, they should talk to
their doctor and take preventive medicines before, during and after the
trip.

The best prevention is to avoid getting bit by mosquitoes. This
includes using effective mosquito repellants and bed-netting so
mosquitoes can’t bite at night during sleep.

Some people who live in malaria-infested areas develop partial
immunity. This immunity is lost if they move to an area that does not
have malaria. Scientists feel that having the condition of sickle-cell
anemia may be an advantage in that the abnormally shaped red blood cells
resist malaria infection.

Surprisingly, malaria has been complicated to develop a vaccine
against. There is a promising potential vaccine currently being tested
in Europe, but it is not commercially available at this time.

Diagnosis
There are several blood tests available to diagnose malaria. Some are
rapid, and some can take several days. The standard test is to look
directly at a patient’s blood and observe the red blood cells that have a
classic appearance when infected by the malaria parasite.

Treatment
Treatment for malaria is based on several factors, including which
malaria parasite the person is infected with, the patient’s age, the
severity of symptoms, and pregnancy status.

Many medicines used to treat malaria are no longer effective. The
history of malaria treatment is marked by developing new, effective
drugs as the parasites develop resistance to the standard, older
medicines. However, the overwhelming majority of patients treated for
malaria will recover fully and have healthy lives.

If you travel to a high-risk malaria region and develop flu-like
symptoms, talk to your doctor about the possibility of being tested for
malaria.

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