World Malaria Day is observed annually every April 25.
Malaria remains to be one of the leading causes of illness and loss of lives in developing countries. In its 2019 report, the World Health Organization recorded an estimate of 228 million cases in 2018 with 405,000 deaths.
The disease is caused by organisms called protozoans and named Plasmodium. Species include Plasmodium falciparum (P. falciparum), which accounts for more than 90 percent of malaria mortalities worldwide, P. vivax, P. malariae, and P. ovale. Plasmodium is transmitted through the bite of an infected female anopheles mosquito. The protozoan parasite is injected from the gut of the mosquito to the skin of a person. The parasite goes to the liver cells, travels to the blood and enters red blood cells.
P. falciparum has been shown to modify the surface of infected red blood cells (RBCs) and render some of these RBCs as “sticky cells”. These attach to the wall of blood vessels and other uninfected red blood cells, and are sequestered in blood vessels.
The lining of blood vessels can be injured and obstruction of small blood vessels can occur. Obstruction of these small blood vessels causes disruption in blood flow and oxygen delivery to important body organs hence causing end-organ damage.
The presence of parasites in the infected person’s blood also activates the immune system leading to the release of inflammatory substances (cytokines) and other toxic products of inflammation that cause further harm to body organs.
In pregnant women, sequestration of RBCs and malarial parasites occur in the placenta and this can lead to preterm delivery, miscarriage, anemia, low birth weight, malaria in the newborn, or still birth.
P. falciparum malaria can be uncomplicated or severe. Initial symptoms are nonspecific (similar to infections from other causes) and these include fever, chills, body pains, headache, loss of appetite, cough, stomach pains, and jaundice or yellowing of the eyes.
Signs and symptoms of severe disease like weakness, convulsions, difficulty in breathing, acute kidney failure, bleeding, shock, and coma usually appear three to seven days after the initial symptoms. Some patients, however, deteriorate rapidly and can die within 24 hours of the initial symptoms.
The classic presentation of malarial infection – shaking chills followed by high grade fever then marked sweating – indicate an infection with P. falciparum. A distinct complication of falciparum malaria is cerebral malaria (involvement of the brain).
Malaria in the Philippines is most commonly caused by P. falciparum and some by P. vivax.
The principal vector (transmitter) is the mosquito anopheles minimusflavirostris which breeds in freshwater streams in foothills and slopes of mountains. It bites during dusk to dawn.
With timely diagnosis and adequate treatment, uncomplicated malaria is associated with full recovery.
Prevention of infection includes the use of personal protective measures, barrier clothing, bed nets impregnated with insecticide, use of effective mosquito repellent and indoor residual spraying.
When traveling to areas where malaria is endemic, use prophylactic drugs. Pregnant women should not travel to endemic areas.
As of 2021, the only approved vaccine for human use against malaria is RTS,S (brand name: Mosquirix). It is given in four doses, injected intramuscularly. Other vaccines are being developed and at least one has shown higher efficacy rate.
Malaria is a preventable and treatable disease. The Department of Health has several programs to attain its goal of a malaria-free Philippines by 2030.
Medical questions and suggestions may be emailed to [email protected] or [email protected].
