Malaria - Symptoms, Prevention and Treatment

infection of red blood cells

Malaria is an infection of red blood cells with the single-celled parasite Plasmodium, which causes fever, an enlarged spleen and anaemia. It mainly occurs in the tropics and sub-tropics. As told above, malaria is caused by a protozoan parasite of the genus Plasmodium, which requires two different hosts during its life cycle : man and mosquito. It is transmitted from man to man by the bite of an infected mosquito.

The mosquito sucks blood from an infected person, taking in the parasite which can then continue its life cycle within the mosquito. Later, when the mosquito bites another human, the parasites pass in with the insect's saliva. Once inside man, the parasites continue to develop in the liver.

From there they reenter the blood stream and multiply inside the red cells, causing them to rupture within two or three days. This rupture of the red cells is responsible for the characteristic chills, fever and sweating of malaria. Parasites released into the bloods stream when the cells rupture can enter other red cells and the life cycle is repeated.

Four species of Plasmodium cause human malaria. Three of them (Plasmodium vivax, Plasmodium falciparum and Plasmodium ovale) repeat the cycle every 48 hours and produce symptoms every third day (tertian malaria), plasmodium malaria repeats the cycle every 72 hours (quartan malaria). Among other consequences of the parasitic infectation and rupture of blood cells are anaemia, jaundice, an enlarged spleen, congestion of blood vessels in the brain, and kidney failure.

Malaria is usually spread by the bite of an infected female mosquito. Very rarely, the disease is transmitted through a transfusion of contaminated blood or an injection with a needle that was previously used by a person with malaria.

Although drugs and insecticides have made malaria rare in the developed countries including United States, the disease remains common and fatal in tropical areas worldwide. There are 300 to 500 million people infected with malaria and one to two million deaths occur each year.

Most of these deaths occur in children younger than 5 years of age. The cycle of malarial infection begins when a female mosquito bites a person with malaria. The mosquito ingests blood that contains malarial parasites. Once inside the mosquito, the parasite multiplies and migrates to the mosquito's salivary gland.

When the mosquito bites another person, the parasites are injected along with the mosquito's saliva. Inside the person, the parasite move to the liver and multiply again. They typically mature over an average of one to three weeks, then leave the liver and invade the person's red blood cells. The parasites multiply yet again inside the red blood cells, eventually causing the infected cells to rupture.

Plasmodium vivax and plasmodium ovale can remain in the liver in a dormant form that periodically releases mature parasites into the blood stream causing recurring attacks of symptoms. Plasmodium falciparam and Plasmodium malariae do not persist in the liver. Mature form of Plasmoduim malariae, however, can persist in the blood stream for months, even years, before causing an attack of symptoms. Malaria caused by Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae tends to be less severe, although these parasites can remain in the blood for long periods, producing fever, chills, headache, poor appetite, fatigue, and a general feeling of illness (malaise). However Falciparum malaria, caused by Plasmodium Falciparam, is the most dangerous form of malaria and can be fatal.

In falciparam malaria, the infected red blood cells often stick to the walls of small blood vessels and clog them, resulting in damage to many organs, particularly the brain (cerebral malaria), lungs and kidney. Cerebral malaria is a particularly dangerous complication that can produce high fever, headache, drowsiness, delirium, confusion, seizure and coma. In falciparam fluid can accumulate in the lungs and cause severe breathing problems. Damage to multiple organs can cause a fall in blood pressure. Cerebral malaria most commonly occurs in infants or young children, pregnant women, and people who travel to high-risk areas.

Symptoms and Complications :

As the infected red blood cells rupture and release parasites, a person suddenly develops a shaking chill followed by a fever that can exceed 1040F. Headache, bodyaches, nausia are common. The fever typically falls after several hours, and heavy sweating occurs. Fevers eventually becomes periodic, occuring at 48 hours intervals with Plasmodium vivax and Plasmodium ovale and at 72 hours intervals with Plasmodium malariae. The fevers caused by Plasmoduim falciparam are often not periodic, but sometimes occur at 48 hour intervals.

As the illness progresses, the spleen enlarges. A decrease in the level of sugar (glucose) in the blood can occur in people infected with Plasmodium falciparam and may be severe in people who have a large number of parasites in their blood - particularly if they are treated with the drug quinine.

Diagnosis :

Malaria should be considered if a febrile patient is in or has recently left a malaria prone locality. Well stained blood films, thin and thick, should be repeated if necessary to confirm the diagnosis. P. falciparam parasites may be scanty, especially in patients treated partially. With P.falciparam, ring forms are normally seen in the early stage. With other species all stages of the erythrocytic cycle may be found. Gametocytes appear after about 2 weeks.

Prevention and Treatment :

Mosquito control measures, which include eliminating breeding areas and killing larvae in the standing water where they live, are very important. People who live in or travel to malaria-infested areas can also take precautions to limit mosquito exposure, such as using insecticide sprays in homes and outbuildings, placing screens on doors and windows, using permethrin-impregnated mosquito netting over beds, and applying mosquito repellents containing DEET on exposed areas of the skin. People can wear long pants and long sleeved shirts, particularly between dusk and dawn, to protect against mosquito bites. People subject to intense mosquito exposure can spray permethrin on their clothing before it is worn.

Vaccines for preventing malaria are still in the experimental stage.

Drugs should be taken to prevent malaria during travel in areas where malaria is prevalent. The preventive drug is started before travel begins, continued throughout the stay, and extended for a period of time that varies for each drug but is usually 4 weeks after the person leaves the high risk area.

Many drugs are used to prevent and treat malaria. Drug resistance is a serious problems, particularly with the dangerous Plasmodiam falciparum species. The prevalence of drug resistant strains varies in different parts of the world. Thus, the choice of drug for prevention varies by geographic location. The choice of drug for treatment is based on the infecting species of Plasmodium and its known or suspected sensitivities.

Chloroquine is the preferred drug for prevention of malaria caused by Plasmodium falciparum in Mexico, areas of Central America west of the Panama Canal, Haiti, the Dominican Republic, and some areas of the Middle East. Strains of Plasmodium falciparum that are resistant to chloroquine are present in most other areas of the world where malaria occurs. In those areas, the recommended preventive drugs include mefloquine, doxycycline, or the combination atovaquone-proguanil.

Chloroquine is the drug of choice for treatment in a person who has malaria caused by Plasmodium vivax, Plasmodum ovale, or Plasmodium malariae- except in a very few areas where resistance to chloroquine in people with Plasmoduim vivax has been reported. Chloroquine also is acceptable for Plasmodium falciparum infections acquired in areas without known drug resistance.

Primaquine is added to kill persistent parasites in the liver of a person infected with Plasmoduim vivax or Plasmodium ovale. Before primaquine is given, a blood test is done to look for a relatively common enzyme deficiency (G6PD deficiency). People with G6PD deficiency who are given primaquine may have a breakdown of their red blood cells.

Falciparum malaria in areas with known chloroquine resistance is treated with quinine plus doxycycline or, if uncomplicated, atovaquoune proguanil. Atovaquone proguanil has fewer side effects than quinine.

Mefloquine can be used but side effects are common. If the person cannot take drugs by mouth, quinidine may be given intravenously under careful observation in the hospital.

Chloroquine is relatively safe and is approved for use in children and pregnant women. Mefloquine sometimes cause nausea, dizziness, and trouble sleeping. It may rarely produce seizures or psychiatric problems. It should also be avoided in people with certain heart conditions.

Quinine is often associated with headache, nausea, vomiting, visual disturbances, and ringing in the ears - a condition known as cinchonism. Quinine may also cause low blood sugar in people infected with Plasmodium falciparum.

Atovaquone proguanil may cause nausea, vomiting, or abdominal pain and is not used in people with poor kidney function, pregnant women, or infants.

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