Plasmodiasis(Malaria)

Nov 10, 2016,

Malaria is a potentially life-threatening disease caused by infection withPlasmodium protozoa transmitted by an infective female Anopheles mosquito.Plasmodium falciparum infection carries a poor prognosis with a high mortality if untreated, but it has an excellent prognosis if diagnosed early and treated appropriately. See the image below.



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Malarial merozoites in the peripheral blood. Note that several of the merozoites have penetrated the erythrocyte membrane and entered the cell.

See 11 Travel Diseases to Consider Before and After the Trip, a Critical Images slideshow, to help identify and manage infectious travel diseases.

Signs and symptoms

Patients with malaria typically become symptomatic a few weeks after infection, though the symptomatology and incubation period may vary, depending on host factors and the causative species. Clinical symptoms include the following:

  • Headache (noted in virtually all patients with malaria)

  • Cough

  • Fatigue

  • Malaise

  • Shaking chills

  • Arthralgia

  • Myalgia

  • Paroxysm of fever, shaking chills, and sweats (every 48 or 72 hours, depending on species)

Less common symptoms include the following:

  • Anorexia and lethargy

  • Nausea and vomiting

  • Diarrhea

  • Jaundice

Most patients with malaria have no specific physical findings, but splenomegaly may be present. Severe malaria manifests as the following:

  • Cerebral malaria (sometimes with coma)

  • Severe anemia

  • Respiratory abnormalities: Include metabolic acidosis, associated respiratory distress, and pulmonary edema; signs of malarial hyperpneic syndrome include alar flaring, chest retraction, use of accessory muscles for respiration, and abnormally deep breathing

  • Renal failure (typically reversible)

See Clinical Presentation for more detail.

Diagnosis

The patient history should include inquiries into the following:

  • Recent or remote travel to an endemic area

  • Immune status, age, and pregnancy status

  • Allergies or other medical conditions

  • Medications currently being taken

The following blood studies should be ordered:

  • Blood culture

  • Hemoglobin concentration

  • Platelet count

  • Liver function

  • Renal function

  • Electrolyte concentrations (especially sodium)

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

  • In select cases, rapid HIV testing

  • 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

The following 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 should be carried out, as follows:

  • Microhematocrit centrifugation (sensitive but incapable of speciation)

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

  • 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

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

  • Presence of early forms in peripheral blood

  • Multiply infected red blood cells

  • Age of infected RBCs

  • Schüffner dots

  • Other morphologic features

See Workup for more detail.

Management

Treatment is influenced by the species causing the infection, including the following:

  • Plasmodium falciparum

  • P vivax

  • P ovale

  • P malariae

  • P knowlesi

In the United States, patients with P falciparum infection are often treated on an inpatient basis to allow observation for complications. Patients with non– P falciparum malaria who are well can usually be treated on an outpatient basis.

General recommendations for pharmacologic treatment of malaria are 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 (only a few areas in Central America and the Middle East): Chloroquine

  • P vivax, P ovale malaria: Chloroquine plus primaquine

  • P malariae malaria: Chloroquine

  • P knowlesi malaria: Same recommendations as for P falciparummalaria

Pregnant women (especially primigravidas) are up to 10 times more likely to contract malaria than nongravid women and have a greater tendency to develop severe malaria. Medications that can be used for the treatment of malaria in pregnancy include the following:

  • Chloroquine

  • Quinine

  • Atovaquone-proguanil

  • Clindamycin

  • Mefloquine (avoid in first trimester)

  • Sulfadoxine-pyrimethamine (avoid in first trimester)

  • Artemether-lumefantrine

  • Artesunate and other antimalarials

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By Gabriel Ugwueke (ID: DOC1780)       Comments       Rating: