INFECTIOUS DISEASE:Understanding Malaria (plasmodium Infection)

INFECTIOUS DISEASE:Understanding Malaria (plasmodium Infection)

Malaria is a parasitic infection transmitted by an infective anopheles mosquito. Victims of malaria usually feel very sick with a high fever and shaking chills.

Malaria is knowly caused by single-celled parasites of the genus plasmodium.

The parasites that cause malaria affect RBCs, therefore people can also catch malaria from exposure to infected blood. Other modes of transmission of malaria:

Blood transfusions

Mother to unborn child

Needles used to inject drugs

Organ transplant

The procces of malaria infection

Once the female anopheles mosquitoe bites you, the parasites (sporozoites) are injected into your body, the parasites then travel to the liver and here they mature in the liver cells (Hepatocytes). After a number of days, the mature parasites now enter the bloodstream and begin to infect Erythrocytes (red blood cells). They develop into trophozoites and then into schizonts over a period of days (Erythrocytic phase). Rupture of infected erythrocytes containing the schizont results in fever and merozoite release. The merozoites enter RBCs, and the process becomes continuous resulting in a increase in parasite burden

The malaria-infected red blood cell showing parasites plasmodium malariae in the schizont stage


A small percentage of parasites become gametocytes, which undergo sexual reproduction when taken up by the mosquito. These can develop into infective sporozoites, which continue the transmission cycle after a blood meal in a new host.

Mosquito feeding 

Signs and symptoms of malaria

How bad malaria symptoms are varies depending on age, general health, and the kind of malaria parasite that you have.

They include:

Nausea and vomiting

General feeling of discomfort




Other symptoms include 


Abdominal pain

Muscle or joint pain


Rapid breathing

Rapid heart rate


Types of Malaria parasites

Malaria is caused by five (5) species of single-cell, eukaryotic Plasmodiumparasites. The plasmodium species can usually be distinguished by morphology on a blood smear.

They include

Plasmodium Falciparum

Plasmodium Ovale

Plasmodium Vivax 

Plasmodium Malariae

Plasmodium knowlesi

1. Plasmodium Falciparum

This species of plasmodium is very deadly and causes a more severe form of the disease and those who contract this form of malaria have a higher risk of death. it causes malignant form of malaria.  P falciparum is able to infect RBCs of all ages, resulting in high levels of parasitemia (>5% RBCs infected).

It can cause:

Cerebral malaria,

Pulmonary edema,

Rapidly developing anemia,

Renal problems: haemoglobinuria also called blackwater fever which is the  darkening of the urine seen with severe RBC breakdown resulting from high parasitemia and is often a sign of impending renal failure and clinical decline.

Other manifestations of P falciparum infection include

Lactic acidosis ( over production of lactic acid)

Hypoglycaemia (Low glucose levels)

Multiorgan dysfunction due to hypoxia.

These severe manifestations occur in travelers without immunity or in children who are situated in endemic areas.

The most important reason why the consequences  infection are so severe is the ability to adhere to Endothelial cell walls, it alsocauses vascular obstruction. When RBCs become nfected with this parasite, the organism produces proteinaceous knobs that bind to endothelial cells. The adherence of these infected RBCs causes them to clump together in the blood vessels in many areas of the body, causing microvascular damage and leading to much of the damage.

The average incubation period of P.falciparum is 9-14 days.

incubation period is refers to the time elapsed between exposure to the infectious agent (through the bite of the Anopheles mosquito) and the manifestation of the first clinical sign or symptom.

2. Plasmodium vivax

When you get infected with P. vivax and no treatment, the infection lasts for up-to 2-3 months with diminishing frequency and intensity of paroxysms. Patients infected with P vivax,

50% experience a relapse within a few weeks to 5 years after the initial illness.

Splenic rupture: secondary to splenomegaly resulting from RBC sequestration.

P vivax infects only immature RBCs, leading to limited parasitemia.

The average incubation period of P.vivax is 12-17 days

3. Plasmodium Ovale

Infection with P. Ovale is similar to P vivax although it’s  usually less severe. P ovale infection can resolve without treatment. Similar to P vivax, P ovale infects only immature RBCs, and parasitemia is usually less than that seen in P falciparum.

P vivax and P ovale have a hypnozoite form, during which the parasite can stay in the liver for months before emerging and inducing recurrence after the initial infection.

P.vivax and P.Ovale exhibit the same incubation period

4. Plasmodium Malariae

Victims of infected with this type of malaria remain asymptomatic for a much longer period of time than do those infected with P vivax or P ovale. Recrudescence is common in persons infected with P malariae. It often is associated with a nephrotic syndrome, resulting from deposition of antibody-antigen complex on the glomeruli


4. Plasmodium Knowlesi

It is thought that simian malaria cases probably also occur in Central America and South America. Patients infected with this, or other simian species, should be treated as aggressively as those infected with falciparum malaria, as P knowlesi may cause fatal disease.

Autochthonous cases have been documented in Malaysian Borneo, Thailand, Myanmar, Singapore, the Philippines, and other neighboring countries

Complications of malaria infection

Most complications are caused by P falciparum.

They include

Seizures If parasite-filled blood cells block small blood vessels to your brain (cerebral malaria), swelling of your brain or brain damage may occur. Cerebral malaria may cause seizures and coma.


Hemoglobinuria (blackwater fever) – Blackwater fever is the passage of dark urine, described as Madeira wine colored; hemolysis, hemoglobinemia, and the subsequent hemoglobinuria and hemozoinuria cause this condition

Noncardiogenic pulmonary edema This affliction is most common in pregnant women and results in death in 80% of patients

Profound hypoglycaemia – it usually occurs in children and pregnant women; it is difficult to diagnose because adrenergic signs are not always present and because stupor already may have occurred in the patient

Renal failure

Lactic acidosis – This occurs when the microvasculature becomes clogged with P falciparum; if the venous lactate level reaches 45 mg/dL, a poor prognosis is very likely

Hemolysis resulting in severe anemia and jaundice

Bleeding (coagulopathy)

Shock, includes a sudden fall in blood pressure

Acute respiratory distress syndrome, which affects breathing


Hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites

Diagnosis of malaria

Patient should include inquiries into the following:

Recent or remote travel to an malaria endemic area

Immune status, age, and pregnancy status

Allergies or other medical conditions

Medications currently being taken

The blood tests need to be done:

Blood smears

Blood culture

Haemoglobin concentration

Platelet count

Liver function test (LFT)

Renal function (RFT)

Serum electrolyte concentration (especially sodium)

Monitoring of parameters suggestive of hemolysis (haptoglobin, lactic dehydrogenase [LDH], reticulocyte count)

White blood cell count: Fewer than 5% of malaria patients have leukocytosis; thus, if leukocytosis is present, the differential diagnosis should be broadened

If the patient is to be treated with primaquine, glucose-6-phosphate dehydrogenase (G6PD) level

If the patient has cerebral malaria, glucose level to rule out hypoglycemia

Imaging studies may be considered:

Chest radiography, if respiratory symptoms are present

Computed tomography of the head, if central nervous system symptoms are present

Specific tests for malaria infection be done as follows:

Microhematocrit centrifugation (sensitive but incapable of speciation)

Thin (qualitative) or thick (quantitative) blood smears (standard): Note that 1 negative smear does not exclude malaria as a diagnosis; several more smears should be examined over a 36-hour period

Alternatives to blood smear testing (used if blood smear expertise is insufficient): Include rapid diagnostic tests, polymerase chain reaction assay, nucleic acid sequence-based amplification, and quantitative buffy coat

Fluorescent dyes/ultraviole indicator tests (may not yield speciation information)

Histologically, the various Plasmodium species causing malaria may be distinguished by the following:

Presence of early forms in peripheral blood (Trophonz

Multiply infected red blood cells

Age of infected RBCs

Sch├╝ffner dots

Other morphologic features

Treatment and prevention of malaria


Pharmacological treatment of malaria is as follows:

P falciparum malaria: Quinine-based therapy is with quinine (or quinidine) sulfate plus doxycycline or clindamycin or pyrimethamine-sulfadoxine; alternative therapies are artemether-lumefantrine, atovaquone-proguanil, or mefloquine

P falciparum malaria with known chloroquine susceptibility: Chloroquine

P vivax, P ovale malaria: Chloroquine plus primaquine

P malariae malaria: Chloroquine

P knowlesi malaria: Same recommendations as for P falciparum malaria

Pregnant women. Medications that can be used for the treatment of malaria in pregnancy include the following:






Sulfadoxine-pyrimethamine (avoid in first trimester)

Artemether-lumefantrine [1]

Artesunate and other antimalarials


Host protective factors

The sickle cell trait (hemoglobin S), thalassemias, hemoglobin C, and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency are protective against death from P falciparum malaria, with the sickle cell trait being relatively more protective compared to the other 3. Individuals with hemoglobin E may be protected against P vivax infection.

Individuals who are heterozygotic for RBC band 3 ovalocytosis are at reduced risk of infection with P falciparum, P knowlesi, and, especially, P vivax malaria.

Persons living in areas of malaria endemicity may develop partial immunity to infection with time and repeated exposure.

Patient Education

Avoid mosquitoes by limiting exposure during times of typical blood meals by

Wearing long-sleeved clothing

using insect repellants.

Avoid wearing perfumes and colognes.

Sleeping under a treated mosquito net

Preventive medicine: Dugs taken to prevent malaria are the same drugs used to treat the disease. What drug you take depends on where and how long you are traveling and your own health.

Vaccine: The World Health Organization (WHO) recommends a malaria vaccine for use in children who live in countries with high numbers of malaria cases.


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