Malaria is an illness caused by the Plasmodium parasite. Most often, the female Anopheles mosquito transmits the disease. The parasite enters the bloodstream following a mosquito bite. There are more than 100 types of Plasmodium, but only five types infect humans. The severity of the illness varies depending on which type of Plasmodium parasite causes the infection. First, the parasite multiplies in the liver, then enters and destroys red blood cells. Symptoms are similar to the flu, but malaria can be long-term and fatal.
P. falciparum causes a severe form of malaria that carries the highest risk of death; infected mothers can also pass this parasite to their babies, called congenital malaria. Although mosquitoes are the most common mode of transmission, malaria can also be transmitted in the same ways as other blood-borne illnesses, which includes through organ transplants, blood transfusions, and shared needles and syringes.
Plasmodium falciparum is the most common type of malaria and is mostly found in Africa. It causes the most deaths worldwide. Plasmodium vivax is prevalent in Asia and South America. Symptoms tend to be mild, but this type can stay dormant in the liver for up to three years. Plasmodium ovale can stay dormant with no symptoms for several years and is found only in West Africa. Plasmodium malariae is also in Africa but very rare. Plasmodium knowlesi is common in southeast Asia.
Stagnant water increases mosquito populations, leading to an increased risk of malaria infection. Wet climates and excessive rainfall produce considerable standing water. Mosquito eggs are left in the water; the process to reach adulthood takes around twelve days. In the right conditions, mosquito numbers can rise dramatically in only a month.
People traveling to areas native to the Plasmodium parasite should take care when visiting. Consult a doctor before taking a trip to known malaria-prone locations. Use preventative measures including netting around sleeping areas, insecticide, and insect repellents. Avoid sleeping outdoors or spending time around stagnant water. Keep skin covered and treat clothing and bed nets with insecticides daily.
People can take medications to prevent malaria before, during, and after travel to at-risk locations. Doctors may recommend continuing the course for up to four weeks after returning home because the parasite can remain in the body long after the bite that caused infection. The purpose of these medications is to eradicate the parasites before they reach the liver or red blood cells. Precautionary medications reduce the risk of infection by 90%.
When a person is infected with the malaria parasite, treatment is dependent on the severity of symptoms. To prescribe the correct medicine, doctors need to know what parasitic species is present and the area the parasite came from. The location is important because many species have become drug resistant. Medical history and pregnancy may also affect treatment options. Outpatient treatment is usually sufficient unless there are complications.
Most medications to treat malaria kill the parasites while they are active in the bloodstream but one drug class can reach theme in the dormant stage. These drugs can be very hard on the body and some cannot be taken by people with a G6PD deficiency or history of kidney disease, or by expectant mothers. A G6PD screening test is essential before giving any drug to treat dormant malaria.
Combination therapy using one of the first anti-malaria drugs can treat uncomplicated malaria, which doctors diagnose in patients who have symptoms, but, as yet, unaffected organs. One drug is very effective in quickly reducing the number of Plasmodium parasites in the bloodstream; it can reduce levels of parasites in the first three days of infection, while a secondary medication eliminates the remainder. Unfortunately, malaria-causing parasites often develop resistance to commonly used combination therapy medications.
Oral malaria medications are most common, but people with severe infections may require intravenous administration. P. falciparum is almost always treated through IV administration. If infection occurs in spite of preventative medications, it is important to avoid readministering the same medications, because they will not be effective. Sometimes doctors try several drugs and drug cocktails before finding one that cures the infection. As drug resistance continues and spreads to new areas, fewer medications are effective. Currently, no new classes of medication to treat malaria are in development.
Treatment for malaria usually results in a good prognosis, but complications are possible. Cerebral malaria can lead to permanent brain damage. Some strains are resistant to more than one medication, so patients require multiple courses of treatment. The P. vivax and P. ovale strains of malaria can stay dormant in the liver for an extended period, then reactivate to cause another active infection requiring more treatment.
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