What is malaria?
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Malaria is an infectious disease caused by a parasite, Plasmodium, which infects red blood cells. Malaria is characterized by cycles of chills, fever, pain, and sweating. Historical records suggest malaria has infected humans since the beginning of mankind. The name "mal aria" (meaning "bad air" in Italian) was first used in English in 1740 by H. Walpole when describing the disease. The term was shortened to "malaria" in the 20th century. C. Laveran in 1880 was the first to identify the parasites in human blood. In 1889, R. Ross discovered that mosquitoes transmitted malaria. Of the four common species that cause malaria, the most serious type is Plasmodium falciparum malaria. It can be life-threatening. However, another relatively new species, Plasmodium knowlesi, is also a dangerous species that is typically found only in long-tailed and pigtail macaque monkeys. Like P. falciparum, P. knowlesi may be deadly to anyone infected. The other three common species of malaria (P. vivax, P. malariae, and P. ovale) are generally less serious and are usually not life-threatening. It is possible to be infected with more than one species of Plasmodium at the same time.
Currently, about 2 million deaths per year worldwide are due to Plasmodium
infections. The majority occur in children under 5 years of
age in sub-Saharan African countries. There are about 400 million new
cases per year worldwide. Most people diagnosed in the U.S. obtained
their infection outside of the country, usually while living or
traveling through an area where malaria is endemic.
What are malaria symptoms and signs?
The symptoms characteristic of malaria include flulike illness with fever, chills, muscle aches, and headache. Some patients develop nausea, vomiting, cough, and diarrhea. Cycles of chills, fever, and sweating that repeat every
one, two, or three days are typical. There can sometimes be vomiting, diarrhea, coughing, and yellowing (jaundice) of the skin and whites of the eyes due to destruction of red blood cells and liver cells.
People with severe P. falciparum malaria can develop bleeding problems, shock, liver or kidney failure, central nervous system problems, coma, and can die from the infection or its complications. Cerebral malaria (coma, or altered mental status or seizures) can occur with severe
P. falciparum infection. It is lethal if not treated quickly; even with treatment, about 15%-20% die.
How is malaria transmitted?
The life cycle of the malaria parasite (Plasmodium) is complicated and involves two hosts, humans and
Anopheles mosquitoes. The disease is transmitted to humans when an infected
Anopheles mosquito bites a person and injects the malaria
parasites (sporozoites) into the blood. This is shown in Figure 1, where
the illustration shows a mosquito taking a blood meal (circle label 1
in Figure 1).
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Figure 1: CDC illustration of the life cycles of malaria parasites, Plasmodium spp. SOURCE: CDC |
Sporozoites travel through the bloodstream to the liver, mature, and
eventually infect the human red blood cells. While in red blood cells, the
parasites again develop until a mosquito takes a blood meal from an infected
human and ingests human red blood cells containing the parasites. Then the
parasites reach the Anopheles mosquito's stomach and eventually invade
the mosquito salivary glands. When an Anopheles mosquito bites a human,
these sporozoites complete and repeat the complex Plasmodium life cycle. P. ovale
and P. vivax can further complicate the cycle by producing dormant stages
(hypnozoites) that may not develop for weeks to years.
Where is malaria a particular problem?
Malaria is a particular problem and a major one in areas of Asia,
Africa, and Central and South America. Unless precautions are taken,
anyone living in or traveling to a country where malaria is present can
get the disease. Malaria occurs in about 100 countries; approximately
40% of the world population is at risk for contracting malaria. To get
information on countries that have current malaria infection problems,
the CDC (Centers for Disease Control) has a constantly updated web site (http://www.cdc.gov/malaria/travelers/
country_table/a.html) that lists the problem areas in detail.
country_table/a.html) that lists the problem areas in detail.
HIV (AIDS)
and malaria co-infection is a significant problem across Asia and
sub-Saharan Africa. Research suggests that malaria and HIV co-infection
can lead to worse clinical outcomes in patients. It seems that
co-infections enhance the disease process of both pathogens.
What is the incubation period for malaria?
The period between the mosquito bite and the onset of the malarial
illness is usually
one to three weeks (seven to 21 days). This initial time period is
highly variable as reports suggest that the range of incubation periods
may range from
four days to one year. The usual incubation period may be increased when
a person has taken an inadequate course of malaria prevention
medications. Certain types of malaria (P. vivax and
P. ovale) parasites can also take much longer, as long as eight
to 10 months, to cause symptoms. These parasites remain dormant
(inactive or hibernating) in the liver cells during this time.
Unfortunately, some of these dormant parasites can remain even after a
patient recovers from malaria, so the patient can get sick again. This
situation is termed relapsing malaria.
How is malaria diagnosed?
Clinical symptoms associated with travel to countries that have
identified malarial risk
(listed above) suggest malaria as a diagnosis. Malaria tests are not
routinely ordered by most physicians so recognition of travel history is
essential. Unfortunately, many diseases can mimic symptoms of malaria
(for example, yellow fever, dengue fever, typhoid fever, cholera, filariasis, and even measles and tuberculosis).
Consequently, physicians need to order the correct special tests to
diagnose malaria, especially in industrialized countries where malaria
is seldom seen. Without the travel history, it is likely that other
tests will be ordered initially. In addition, the long incubation
periods may tend to allow people to forget the initial exposure to
infected mosquitoes.
The classic and most used diagnostic test for malaria is the blood smear
on a microscope slide that is stained (Giemsa stain) to show the
parasites inside red blood cells (see Figure 2).
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| Figure 2: CDC slide of a Giemsa stained smear of red blood cells showing Plasmodium malariae and Plasmodium falciparum parasites. SOURCE: CDC/Steven Glenn, Laboratory & Consultation Division |
Although this test is easily done, correct results are dependent on the technical skill of the lab technician who prepares and examines the slides with a microscope. Other tests based on immunologic principles exist; including RDTs (rapid diagnostic tests) approved for use in the U.S. in 2007 and polymerase chain reaction (PCR) tests. These are not yet widely available and are more expensive than the traditional Giemsa blood smear. Some investigators suggest such immunologic based tests be confirmed with a Giemsa blood smear.
What is the treatment for malaria?
Three main factors determine treatments: the infecting species of Plasmodium
parasite, the clinical situation of the patient (for
example, adult, child, or pregnant female with either mild or severe
malaria), and the drug susceptibility of the infecting parasites. Drug
susceptibility is determined by the geographic area where the infection
was acquired. Different areas of the world have malaria types that are
resistant to certain medications. The correct drugs for each type of
malaria must be prescribed by a doctor who is familiar with malaria
treatment protocols. Since people infected with
P. falciparum malaria can die (often because of delayed treatment), immediate treatment for
P. falciparum malaria is necessary.
Mild malaria can be treated with oral medication; severe malaria (one or
more symptoms of either impaired consciousness/coma, severe anemia, renal failure, pulmonary edema, acute respiratory distress syndrome, shock, disseminated intravascular coagulation, spontaneous bleeding, acidosis, hemoglobinuria [hemoglobin in the urine], jaundice, repeated generalized convulsions, and/or parasitemia [parasites in the blood] of > 5%) requires intravenous (IV) drug treatment and fluids
in the hospital.
Drug treatment of malaria is not always easy. Chloroquine phosphate
(Aralen) is the drug of choice for all malarial parasites except for chloroquine-resistant
Plasmodium strains. Although almost all strains of P. malariae are susceptible to chloroquine,
P. falciparum, P. vivax, and even some P. ovale
strains have been reported as resistant to chloroquine. Unfortunately,
resistance is usually noted by drug-treatment failure in the individual
patient. There are, however, multiple drug-treatment protocols for
treatment of drug-resistant
Plasmodium strains (for example, quinine sulfate plus doxycycline
[Vibramycin, Oracea, Adoxa, Atridox] or tetracycline
[Achromycin], or clindamycin
[Cleocin], or atovaquone-proguanil
[Malarone]). There are specialized labs that can test the patient's
parasites for resistance, but this is not done frequently. Consequently,
treatment is usually based on the majority of
Plasmodium species diagnosed and its general drug-resistance
pattern for the country or world region where the patient became
infested. For example,
P. falciparum acquired in the Middle East countries is usually susceptible to
chloroquine, but if it's acquired in sub-Sahara African countries, it's usually resistant to chloroquine.
The WHO's treatment policy, recently established in 2006, is to treat all cases of uncomplicated
P. falciparum malaria with artemisinin-derived combination
therapy (ACTs). ACTs are drug combinations (for example,
artesunate-amodiaquine, artesunate-mefloquine, artesunate-pyronaridine,
dihydroartemisinin-piperaquine, and chlorproguanil-dapsoneartesunate)
used to treat drug-resistant
P. falciparum. Unfortunately, as of 2009, a number of P. falciparum-infected individuals have parasites resistant to ACT drugs.
New drug treatments of malaria are currently under study because Plasmodium
species continue to produce resistant strains that frequently spread to
other areas. One promising drug class under investigation is the
spiroindolones, which have been effective in stopping
P. falciparum experimental infections.
Is malaria a particular problem during pregnancy?
Yes. Malaria may pose a serious threat to a pregnant woman and her
fetus. Malaria infection in pregnant women may be more severe than in
women who are not pregnant. Malaria may also increase the risk of
problems with the pregnancy,
including prematurity, abortion, and stillbirth. Statistics indicate
that in
sub-Saharan Africa, between 75,000-200,000 infants die from malaria per
year; worldwide estimates
indicate about 2 million children die from malaria each year. Therefore,
all
pregnant women who are living in or traveling to a malaria risk area
should
consult a doctor and take prescription drugs (for example,
sulfadoxine-pyrimethamine) to avoid contracting malaria. Treatment of
malaria in the pregnant female is similar to the usual treatment
described above; however, drugs such as primaquine
(Primaquine), tetracycline (Achromycin, Sumycin), doxycycline, and halofantrine (Halfan) are not recommended as they may harm the fetus. In addition to monitoring the patient for anemia, an OB/GYN specialist
often is consulted for further management.
Is malaria a particular problem for children?
Yes. All children, including young infants, living in or traveling to malaria risk areas should take antimalarial drugs (for
example, chloroquine and mefloquine
[Lariam]). Although the recommendations for most antimalarial drugs are
the same as for adults, it is crucial to use the correct dosage for the
child. The dosage of drug depends on the age and weight of the child. A
specialist in pediatric infectious diseases is recommended for
consultation in prophylaxis (prevention) and treatment of children.
Since an overdose of an antimalarial drug can be fatal, all antimalarial
(and all other) drugs should be stored in childproof containers well
out of the child's reach.
How do people avoid getting malaria?
If people must travel to an area known to have malaria, they need to
find out which medications to take, and take them as prescribed. Current
CDC recommendations suggest individuals begin taking antimalarial drugs
about one to two weeks before traveling to a malaria infested area and
for four weeks after leaving the area (prophylactic or preventative
therapy). Doctors, travel clinics, or the health department can advise
individuals as to what medicines to take to keep from getting malaria.
Currently, there is no vaccine available for malaria, but researchers
are trying to develop one.
Avoid travel to or through countries where malaria occurs if possible.
If people must go to areas where malaria occurs, they should take all of
the prescribed preventive medicine. In addition, the 2010 CDC
international travel recommendations suggest the following precautions
be taken in malaria and other disease-infested areas of the world; the
following CDC recommendations are not unique for malaria
but are posted by the CDC in their malarial prevention publication.
- Avoid outbreaks: To the extent possible, travelers should avoid traveling in areas of known malaria outbreaks. The CDC Travelers' Health web page provides alerts and information on regional disease transmission patterns and outbreak alerts (http://www.cdc.gov/travel).
- Be aware of peak exposure times and places: Exposure to arthropod bites may be reduced if travelers modify their patterns of activity or behavior. Although mosquitoes may bite at any time of day, peak biting activity for vectors of some diseases (for example, dengue, chikungunya) is during daylight hours. Vectors of other diseases (for example, malaria) are most active in twilight periods (for example, dawn and dusk) or in the evening after dark. Avoiding the outdoors or focusing preventive actions during peak hours may reduce risk.
- Wear appropriate clothing: Travelers can minimize areas of exposed skin by wearing long-sleeved shirts, long pants, boots, and hats. Tucking in shirts and wearing socks and closed shoes instead of sandals may reduce risk. Repellents or insecticides such as permethrin can be applied to clothing and gear for added protection; this measure is discussed in detail below.
- Check for ticks: Travelers should be advised to inspect themselves and their clothing for ticks during outdoor activity and at the end of the day. Prompt removal of attached ticks can prevent some infections.
- Bed nets: When accommodations are not adequately screened or air conditioned, bed nets are essential to provide protection and to reduce discomfort caused by biting insects. If bed nets do not reach the floor, they should be tucked under mattresses. Bed nets are most effective when they are treated with an insecticide or repellent such as permethrin. Pretreated, long-lasting bed nets can be purchased prior to traveling, or nets can be treated after purchase. The permethrin will be effective for several months if the bed net is not washed. (Long-lasting pretreated nets may be effective for much longer.)
- Insecticides: Aerosol insecticides, vaporizing mats, and mosquito coils can help to clear rooms or areas of mosquitoes; however, some products available internationally may contain pesticides that are not registered in the United States. Insecticides should always be used with caution, avoiding direct inhalation of spray or smoke.
- Optimum protection can be provided by applying repellents. The CDC recommended insect repellent should contain up to 50% DEET (N,N-diethyl-m-toluamide), which is the most effective mosquito repellent for adults and children over 2 months of age.
What is the prognosis (outcome) for people with malaria?
The majority of people who become infected with P. malariae, vivax, or ovale do well and the fevers abate after about 96 hours. However, in endemic areas, reinfection is common. Malaria caused by
P. falciparum or P. knowlesi, even when treated, have
outcomes ranging from fair to poor, depending on how the parasites react
to treatment. Untreated people often die from these infections. In
general, patients
who are infants, children under the age of 5 (especially in sub-Saharan
countries), and those with depressed immune systems (for
example, AIDS or cancer patients) have a more guarded prognosis.
Where can people get more information about malaria?
"The History of Malaria, an Ancient Disease," Centers for Disease Control and Prevention
"About Malaria," Centers for Disease Control and Prevention
Traveler's Health - Yellow Book, Centers for Disease Control and Prevention
"Malaria," eMedicine.com
Malaria At A Glance
- Malaria is a disease caused by Plasmodium spp. parasites that infects about 400 million people per year with about 2 million deaths.
- Symptoms include recurrent cycles (every one to three days) of fever, chills, muscle aches, headaches; nausea, vomiting, and jaundice also may occur.
- Anopheles mosquitoes transmit the parasites to humans when they bite. The parasites undergo a complicated life cycle in both mosquitoes and humans; the cycle begins again when the mosquitoes take a blood meal from a human that is contaminated with mature parasites.
- Africa, Asia, and Central and South America are the areas with high numbers of malarial infections.
- The incubation period for malaria symptoms is about one to three weeks but may be extended to eight to 10 months after the initial infected mosquito bites occur. Some people may have dormant parasites that may get reactivated years after the initial infection.
- Malaria is diagnosed by the patient's history of recurrent symptoms and the identification of the parasites in the patient's blood, usually by a Giemsa blood smear.
- Malaria is usually treated by using combinations of two or more anti-parasite drugs incorporated into pills that are taken before exposure (prophylactic or preventative therapy) or during infection. More serious infections are treated by IV anti-parasitic drugs in the hospital.
- Infants, children, and pregnant females, along with immunodepressed patients are at higher risk for worse outcomes when infected with malaria parasites.
- To reduce the chance of getting malaria, people should avoid malaria-endemic areas of the world, use mosquito repellents, cover exposed skin, and use mosquito netting covered areas when sleeping.
- The prognosis for the majority of malaria patients is good; most recover with no problems, unless infected with P. falciparum or P. knowlesi, which may have fair to poor outcomes unless treated immediately. Infants, children under 5 years of age, pregnant females, and those with depressed immune systems frequently have a fair to poor prognosis unless effectively treated early in the infection.
REFERENCES:
D'Acremont, V., C. Lengeler, and B. Genton. "Reduction in the Proportion of Fevers Associated With Plasmodium falciparum Parasitaemia in Africa: A Systematic Review." Malaria Journal 9.240 Aug. 22, 2010 doi:10.1186/1475-2875-9-240.
Rottmann, M., C. McNamara, B. Yeung, et al. "Spiroindolones, a Potent Compound Class for the Treatment of Malaria." Science 329 (2010): 1175-1180.
Last Editorial Review: 10/8/2010
Comment from: Glenn, 35-44 Male (Patient)
Published: July 16
I am a Survivor of malaria strain P.falciparum. First signs were
typical cold and flu for a day then a good run for 4 days then a cyclic
pattern of recurring symptoms over the next few days in 24hr cycles.
Each recurrence was worse than the previous. The lead-in took about 7 to
8days. The symptoms eventually did not give any further relief days and
the cycles melded into bad and worse days. Starting now at day 1, the
symptoms worsened to lethargy, lack of concentration and shortness of
breath along with normal flu aches and pains. A visit to the local
medical centre for suspect flu on day 1, routine malaria tests were
negative. I am feeling slightly better on day 2, but certainly not
functional. I am back to the medical centre on day 3 and doctor was
convinced by looking at me, that I had a strain of malaria. More routine
tests returned another negative result so back to the lounge room
floor. The next day now day 4, I could lay dead still for 4 to 6 hours
and only move to go to the toilet. Returning to the floor, my heart rate
was at about 160bpm and the energy exerted required a good 4 hour rest
again. On day 5 and the third visit to the medical centre, the blood
test came back positive and the strain was identified. The doctor
sincerely concerned with the strain identified and the duration of my
illness. I was medivac'd to Australia. Further medication was given on
arrival. Full Recovery took 9 months, but damage was done. For 2 to 3
months I remained on the lounge room floor. During the 3rd and 4th
month, I had to train my muscles to walk again at the local shopping
centre. By the end of the 5th month I could walk one full length of a
shopping centre. A further 4 months passed with daily walks before I was
back to normal. By the 12th month I was struck by depression and then
spent 3 months working out of it, but that's another story.
Related Reading: malaria | flu | depression
Comment from: Malcolm, 55-64 Published: September 20
I had malaria in 1980 when I was working in Kenya. I spent six
weeks in the hospital and lost a lot of weight, which made me very weak
for weeks after. After a few years, I visited Bali. While I was there, I
was bitten by a mosquito on the leg and had to have an injection
because my leg had swollen up so bad. I had a difficult time walking. I
have found over the years that when I get bitten by a mosquito, I get a
swelling to the area.
Comment from: Bel-Jozzie SA, 45-54 Female (Patient) Published: August 18
Tomorrow I will get to find out if I contracted malaria! I was in
Mozambique years ago not hot, pleasant time to go, but first evening I
got bitten! I sprayed my bitten area and rest of the body with "Peaceful
Sleep" repellant aerosol. It was the third trip to this part of
Mozambique. A week later, not even I got fever blisters on my top lip
(almost occupied the whole upper lip). Thinking my immune system is
down, just used fever blister cream and it took basically two weeks to
recover. Whilst recovering I started getting nauseous. Funny sensation
in my stomach did not do well with smells or car trips. Last week
Thursday I got up had 1/3 of the cup of coffee, then took my BP
medication and I went back to bed, as body was saw (like fever type)
chest was sore, (could not even smoke) as I got in I had to get up to go
and vomit. There after experienced weird body pains and I was extremely
cold, shivers and lower back pains! I could not eat, I just wanted tea,
but slept the entire day and night. The next day I thought I had the
energy to go back to work, had a bath, but forget it went back into bed.
Over the weekend I felt slightly better but the nausea was still there.
It is just a weird sensation! You feel you are not right! I feel my
eyes are getting blurry and it feels like there is sand in them! I wake
up sweaty in the mornings even though it's freezing cold here. Today
decided to go to doctor and I described the symptoms to the doc and he
asked if I recently visited malaria stricken area! He also noted I had
fever blisters- (slight red traces on upper lip). He then told me it
sounds like I got malaria! I will get my blood results tomorrow and hope
that its still in early stages as I am a sufferer of PKD (Polycystic
Kidney Disease) and reading other comments has scared the living
daylight out of me. I will comment back with feed back if it was
positive or negative.
Related Reading: Sleep | fever | Polycystic Kidney Disease
Comment from: 25-34 Female (Patient) Published: September 17
I contracted malaria after a beach holiday in Mozambique. The
first sign was a flu-like ache in my joints, followed by a mild
headache, then a fever, which broke some hours later in the night in a
torrent of sweat! A severe headache and pain in my shoulders and lower
back, along with horrible nausea took me to bed for an afternoon and a
night, but I had already started treatment with a drug called Coartem
20/120 (artemether lumefantrine). After that second horrid night, the
fevers and chills stopped, but the sweating occurred on and off in
milder and milder form until the third day.
Related Reading: headache
Comment from: faithie, Female (Caregiver) Published: April 05
When I had malaria, I always had aches and pains, a bitter mouth, and body pains.
