Malaria

Malaria?

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 species of malaria, the most serious type is Plasmodium falciparum malaria. It can be life-threatening. The other three species of malaria (P. vivax, P. malariae, and P. ovale) are generally less serious and are not life-threatening.

How is malaria transmitted?

The life cycle of the parasite is complicated and involves two hosts, humans and Anophelesmosquitoes. The disease is transmitted to humans when an infected Anophelesmosquito bites a person and injects the malaria parasites (sporozoites) into the blood. 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 Anophelesmosquito's stomach and eventually invade the mosquito salivary glands. When anAnopheles 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.

What are the signs and symptoms of malaria?

The symptoms characteristic of malaria include flu-like 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.

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 listed above, when associated with travel to countries that have identified malarial risk, suggest malaria as a diagnosis. Malaria tests are not routinely ordered by most physicians in developed countries so recognition of travel history is essential.

The classic and most used test is the blood smear on a microscope slide that is stained (Giemsa stain) to show the parasites inside red blood cells. 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 RDT's (rapid diagnostic tests) approved for use in the U.S. in 2007 and the 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.

How is malaria treated?

Three main factors determine treatments: the infecting species ofPlasmodium 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

Drug treatment of malaria is not always easy. Chloroquine phosphate 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 acquired in sub-Sahara African countries, is usually resistant to chloroquine.

Is malaria a particular problem during pregnancy?

Yes. Malaria may pose a serious threat to a pregnant woman and her pregnancy. 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 over 1 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 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. 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 I keep from getting malaria?

If you are traveling to an area known to have malaria, find out which medications you need 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. Your doctor, travel clinic, or the health department can advise you 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.

What other precautions should I take to avoid malaria?

If possible, avoid travel to or through countries where malaria occurs. If you must go to areas where malaria occurs, take the prescribed preventive medicine. In addition, the 2008 CDC international travel recommendations suggest the following precautions be taken in malaria infested areas:

• Avoid exposure to mosquitoes during the early morning and early evening hours between the hours of dusk and dawn (the hours of greatest mosquito activity).
• Wear appropriate clothing (long-sleeved shirts and long pants, for examples) especially when you are outdoors.
• Apply insect repellent to the exposed skin. The CDC recommended insect repellent should contains 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.
• Spray mosquito repellents on clothing to prevent mosquitoes from biting through thin clothing.
• Use a permethrin-coated (or similar repellant) mosquito net over your all beds.
• Have screens over cover windows and doors.
• Spray permethrin or a similar insecticide in the bedroom before going to bed.