MALARIA

MALARIA

1. What is malaria?
2. What are malaria symptoms and signs?
3. How is malaria transmitted?
4. Where is malaria a particular problem?
5. What is the incubation period for malaria?
6. How is malaria diagnosed?
7. What is the treatment for malaria?
8. Is malaria a particular problem during pregnancy?
9. Is malaria a particular problem for children?
10. How do people avoid getting malaria?

What is 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 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 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).

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 AnophelesPlasmodium life cycle. P. ovaleP. vivax can further complicate the cycle by producing dormant stages (hypnozoites) that may not develop for weeks to years.
Where is malaria a particular                                                                                                                 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.
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.