MalariaMalaria

DefinitionDefinition

Malaria is a Malaria is a mosquito-borne -borne infectious disease of humans caused by of humans caused by eukaryotic protists of the genus of the genus Plasmodium. It is widespread in . It is widespread in tropical and subtropical regions, including much of and subtropical regions, including much of Subsaharan Subsaharan Africa, , Asia and the and the Americas. . The disease results from the multiplication The disease results from the multiplication of malaria parasites within of malaria parasites within red blood cells, , causing symptoms that typically include causing symptoms that typically include fever and and headache, in severe cases , in severe cases progressing to progressing to coma, and death., and death.

Etiology Etiology

Malaria is caused by obligate Malaria is caused by obligate intracellular protozoan parasites of intracellular protozoan parasites of the genus the genus "Plasmodium".. The four The four species of human malarial parasites species of human malarial parasites are:are:

Plasmodium vivaxPlasmodium vivax P falciparumP falciparum P malariaeP malariae P ovaleP ovale..

Signs and symptomsSigns and symptoms

Signs and symptoms:Signs and symptoms:

fever shiveringshivering arthralgia (joint pain)arthralgia (joint pain) vomiting, anemia (caused by vomiting, anemia (caused by

hemolysis)hemolysis) hemoglobinuriahemoglobinuria retinal damageretinal damage convulsionsconvulsions

Mode of transmission Mode of transmission

Malaria is transmitted by the Malaria is transmitted by the bite of an infective female Anopheles bite of an infective female Anopheles mosquito. Rarely, transmission can mosquito. Rarely, transmission can be congenital (via the placenta) or be congenital (via the placenta) or can occur through transfusions or can occur through transfusions or the use of contaminated needles.the use of contaminated needles.

Period of Period of communicability communicability

Malaria is not directly communicable Malaria is not directly communicable from person to person, except through from person to person, except through congenital transmission; however, during congenital transmission; however, during parasitemia, the disease may be parasitemia, the disease may be transmitted to other persons through blood transmitted to other persons through blood transfusion or through shared, transfusion or through shared, contaminated needles. Infected human contaminated needles. Infected human hosts can be a source of infection for hosts can be a source of infection for Anopheles mosquitoes for prolonged Anopheles mosquitoes for prolonged periods of time (1-3 or longer, depending periods of time (1-3 or longer, depending on the species of malaria) if not adequately on the species of malaria) if not adequately treated. treated.

Susceptibility and Susceptibility and resistance resistance

The role of red blood cell polymorphisms in resistance and The role of red blood cell polymorphisms in resistance and susceptibility to malaria.susceptibility to malaria.

In regions highly endemic for Plasmodium falciparum malaria, In regions highly endemic for Plasmodium falciparum malaria, red cell polymorphisms that confer resistance to severe disease red cell polymorphisms that confer resistance to severe disease are widespread. Sickle cell trait, alpha-thalassemia, glucose-6-are widespread. Sickle cell trait, alpha-thalassemia, glucose-6-phosphate dehydrogenase deficiency, and blood groups were phosphate dehydrogenase deficiency, and blood groups were determined in 100 children from Gabon with severe malaria who determined in 100 children from Gabon with severe malaria who were matched with 100 children with mild malaria and followed were matched with 100 children with mild malaria and followed up for evaluation of reinfections. The sickle cell trait was up for evaluation of reinfections. The sickle cell trait was significantly associated with mild malaria and blood group A with significantly associated with mild malaria and blood group A with severe malaria. During follow-up, the original severe cases had severe malaria. During follow-up, the original severe cases had significantly higher rates of reinfection than the original mild significantly higher rates of reinfection than the original mild cases, with higher parasitemia and lower hematocrit values. cases, with higher parasitemia and lower hematocrit values. Incidence rates did not differ in the context of erythrocyte Incidence rates did not differ in the context of erythrocyte polymorphisms, but patients with sickle cell trait presented with polymorphisms, but patients with sickle cell trait presented with markedly lower levels of parasitemia than those without. Thus, markedly lower levels of parasitemia than those without. Thus, the severity of malaria is partly determined by the presence of the severity of malaria is partly determined by the presence of blood group A and the sickle cell trait. The different presentation blood group A and the sickle cell trait. The different presentation of reinfections in severe versus mild cases probably reflects of reinfections in severe versus mild cases probably reflects different susceptibility to malaria.different susceptibility to malaria.

Methods of control Methods of control

removing or poisoning the breeding removing or poisoning the breeding grounds of the mosquitoes or the grounds of the mosquitoes or the aquatic habitats of the larva stages, aquatic habitats of the larva stages, for example by filling or applying oil for example by filling or applying oil to places with standing water to places with standing water

Using of bednetsUsing of bednets spraying with DDT .spraying with DDT .

Program for prevention Program for prevention The Malaria Research Program of the Research The Malaria Research Program of the Research

Institute for Tropical MedicineInstitute for Tropical Medicine has provided has provided research activities on disease epidemiology and research activities on disease epidemiology and immunology, molecular biology of the parasite, immunology, molecular biology of the parasite, vector behavior, social health research on treatment vector behavior, social health research on treatment patterns and disease perceptions, clinical trials for patterns and disease perceptions, clinical trials for anti-malarial drugs and malaria diagnostic kits, anti-anti-malarial drugs and malaria diagnostic kits, anti-malarial drug resistance and pharmacokinetic malarial drug resistance and pharmacokinetic studies and community-based strategies to improve studies and community-based strategies to improve disease control.disease control.

The The Global Malaria Programme (GMP)Global Malaria Programme (GMP) is is responsible for malaria surveillance, monitoring and responsible for malaria surveillance, monitoring and evaluation, policy and strategy formulation, evaluation, policy and strategy formulation, technical assistance, and coordination of WHO's technical assistance, and coordination of WHO's global efforts to fight malaria. global efforts to fight malaria.

DiagnosisDiagnosis

Antigen testsAntigen testsTests use finger-stick or venous Tests use finger-stick or venous

bloo, the completed test takes a total of bloo, the completed test takes a total of 15-20mins., and results are read 15-20mins., and results are read visually as the presence or absence of visually as the presence or absence of colored stripes on the dipstick.colored stripes on the dipstick.

Molecular methodsMolecular methods

polymerase chain reactionpolymerase chain reaction

Prevention and control Prevention and control /treatment/treatment Early diagnosis and prompt treatmentEarly diagnosis and prompt treatment Vector control – insecticide-treated Vector control – insecticide-treated

mosquito net as main vector control mosquito net as main vector control strategy, complemented by indoor strategy, complemented by indoor residual sprayingresidual spraying

early management and disease early management and disease surveillancesurveillance

monitoring and evaluation – drug and monitoring and evaluation – drug and insecticide resistance monitoringinsecticide resistance monitoring

Antimalarial drugsAntimalarial drugs