Malaria: Clinical sciences

Malaria is a systemic, febrile illness caused by the protozoan parasite Plasmodium. It’s typically seen in recent travelers of endemic regions such as Africa, South Asia, and parts of Central and South America.

Once transmitted via an infected female Anopheles mosquito, the parasites invade hepatic cells where they reproduce. Next, the parasites invade red blood cells, eventually causing their rupture and causing symptoms like fever, malaise, and chills. Based on the presence and degree of parasitemia, you can diagnose your patient with uncomplicated malaria or severe malaria.

Now, if your patient presents with chief concerns suggesting malaria, you should first perform an ABCDE assessment to determine if your patient is unstable or stable. If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and start IV fluids. Then put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry. Finally, if needed, provide supplemental oxygen to maintain oxygen saturation greater than 90%.

Once you stabilize your patient, proceed with a focused history and physical and order labs, primarily CMP, CBC, and coagulation studies, such as a PT and PTT. The history typically reveals fever, seizures, and recent travel to a malaria-endemic area. Physical examination will likely reveal an elevated temperature, hypotension, tachypnea, and altered level of consciousness. Some patients may even present with recurrent seizures and coma!

Here’s a clinical pearl to keep in mind! Cerebral malaria is a diffuse symmetric encephalopathy caused by parasites adhering to the cerebrovascular endothelium, and puts the patient at risk of permanent neurologic damage or death! If you suspect cerebral malaria, immediately treat with intravenous artesunate to reduce the patient’s risk of permanent neurologic damage or death!

Next, lab results are non-specific and could reveal hypoglycemia, low bicarbonate, elevated BUN and creatinine, low hemoglobin and platelets, and elevated PT and PTT.

Now, if your patient is presenting with these findings, suspect severe malaria and obtain a thin and thick Giemsa-stained blood smear. If microscopy reveals no Plasmodium parasites identified, consider an alternative diagnosis. However, if the microscopy reveals Plasmodium parasites you should diagnose severe malaria and start intravenous artesunate.

And here’s one high-yield fact to keep in mind! In the early stage of the infection, the blood smears could reveal no parasites at all! So, if you have a high clinical suspicion of malaria, start the treatment immediately! Next, repeat the blood smears every 12 to 24 hours for three days to confirm your diagnosis. If blood smears reveal no Plasmodium after three days, you can rule out malaria and stop the treatment.

Now, let’s go back to the ABCDE assessment and take a look at stable individuals. If your patient is stable, first obtain a focused history and physical examination. Your patient will usually report periodic fever, myalgia, and fatigue, as well as recent travel to a malaria-endemic area. Additionally, on a physical exam, you might find an enlarged liver or spleen, or even mild jaundice.

Here’s a high-yield fact! There’re many species of Plasmodium, and they may present with various fever patterns. Plasmodium malariae causes quartan fever, where the fever episodes occur every 72 hours, or every fourth day, and are generally milder than other types. Plasmodium vivax and Plasmodium ovale can cause tertian fever, where the episodes occur every 48 hours, or every third day. Plasmodium knowlesi is associated with quotidian fever, where the episodes occur every 24 hours, or every second day. Lastly, Plasmodium falciparum often presents with an irregular fever pattern, without a distinct periodicity like the other types, and tends to be more severe with potentially life-threatening complications.

At this point you should suspect malaria, so don’t forget to obtain a thin and thick Giemsa-stained blood smear for evaluation under microscopy. The thin smear identifies the type of Plasmodium species within red blood cells and is also used to calculate parasite density, expressed as percent parasitemia. On the other hand, the thick smear is a larger sample of blood that contains lysed red blood cells, and while it identifies Plasmodium species, it cannot calculate parasite density!

Now, here’s a clinical pearl! In malaria-endemic areas without access to extensive laboratory testing, you can use malaria rapid diagnostic tests, or RDTs for short. However, keep in mind that this type of testing cannot identify the Plasmodium species or measure parasitemia, so treatment is based on the region’s predominant Plasmodium species and drug resistance patterns.