Malaria classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Yazan Daaboul, Serge Korjian, Alison Leibowitz [2], Marjan Khan M.B.B.S.[3]

Overview

The classification of malaria can be established according to the strains of Plasmodium species. There are five common Plasmodium species that infect humans: P. falciparum, P. ovale, P. vivax, P. malariae, and P. knowlesi. Malaria can also be classified according to severity of infection: uncomplicated vs. severe.

Classification

Classification by Plasmodium Strain

The following Plasmodium strains are the most common strains implicated in human malarial infection.

Comparison of Plasmodium Species Implicated in Human Malaria

Strain	Appearance of Erythrocyte (RBC)	Appearance of Parasite	Clinical Significance
P. falciparum	Normal appearance with Maurer's clefts: Ring, trophozoite, and schizont forms. Distorted appearance: Gametocyte form	Chromatin dots and "appliqué" (accolé): Ring form Clump of mass and dark pigment: Trophozoite and schizont forms Crescent or sausage shape: Gametocyte form	Tertian/subtertian fever (every 48 hours), causes severe malaria in up to 24% of cases, and is frequently drug resistant.
P. vivax	Normal with fine Schüffner dots: Ring form Enlarged with fine Schüffner dots: Trophozoite, schizont, and gametocyte forms	Large cytoplasm with pseudopods: Ring form Large ameboid cytoplasm with yellow-brown pigment: Trophozite form Large mass that fills RBC with yellow-brown coalescent pigment: Schizont form Large mass that fills RBC with scattered brown pigment: Gametocyte form	Tertian fever (every 48 hours), results in severe malaria in up to 22% of cases, and is frequently drug resistant. Relapse is common due to the dormant liver phase.
P. ovale	Normal with fine Schüffner dots	Sturdy cytoplasm and large chromatin: Ring form Compact cytoplasm with dark-brown pigment: Trophozoite form Large nuclei clustered around mass of dark-brown pigment: Schizont form Round to oval form that fills RBC with scattered brown pigment: Gametocyte form	Tertian fever (every 48 hours), rarely causes severe malaria or drug resistance. Relapse is common due to dormant liver phase.
P. malariae	Normal with Ziemann's stippling	Sturdy cytoplasm and large chromatin: Ring form Compact cytoplasm with occasional band forms and coarse dark-brown pigment: Trophozoite form Large nuclei clustered around a mass of coarse, dark-brown pigment and occasional rosettes: Schizont form Round to oval form that fills RBC with scattered brown pigment: Gametocyte form	Quartan fever (every 72 hrs), rarely results in severe malaria or drug resistance. Although dormant liver phase is uncommon, infection persistence is frequently demonstrated.
P. knowlesi	Normal with Sinton and Mulligan stippling	Delicate cytoplasm with appliqué (accolé) forms: Ring form Compact cytoplasm and large chromatin with band forms and dark-brown pigment: Trophozoite form Segmentation with large nuclei around a mass of coarse brown pigment and occasional rosettes: Schizont form Round to oval form that fills RBC with scattered brown pigment: Gametocyte form	Daily fevers, may result in severe malaria in up to 10% of cases, although resistance is rare.

^{Adapted from Center for Disease Control and Prevention (CDC) - Malaria}

Classification by Severity of Infection

The following table classifies malarial infections by severity.

Comparison of Malaria Infections According to Severity

Severity	Clinical Significance
Uncomplicated	Attack lasts 6-10 hours consisting of 3 stages: Cold stage: Shivering Hot stage: Fever, vomiting, and seizure Sweating stage: Sweating and fatigue Non-specific symptoms: Chills Sweating Headache Nausea and vomiting Body aches General malaise Physical findings: Fever Tachypnea Perspiration Weakness Hepatosplenomegaly Jaundice
Severe	Malaria is complicated by organ damage and is considered a medical emergency that requires prompt hospitalization. Cerebral malaria: Altered mental status, seizures, coma, and neurological deficit Hemolytic anemia: Hemoglobinuria, jaundice, and splenomegaly Coagulopathy Acute respiratory distress syndrome (ARDS): Dyspnea, cough, and hypoxia Cardiovascular collapse Acute kidney injury Metabolic acidosis Hypoglycemia
Adapted from Center for Disease Control and Prevention (CDC) - Malaria