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.
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.
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.
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.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.
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.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.
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.
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
reference :
http://www.medicinenet.com/malaria/
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