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A 38-year-old man complaining of cyclic fevers and headaches...

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asked Mar 28, 2017 in Microbiology by Rajesh Bahara
A 38-year-old man comes to the emergency department complaining of cyclic fevers and headaches. The fevers began about 1 week ago; 2 weeks ago the patient returned from a trip to Africa. Physical examination reveals splenomegaly, and brain imaging shows signs of significant cerebral involvement. Which of the following parasites most likely caused this patient’s symptoms?
(A) Babesia microti
(B) Plasmodium falciparum
(C) Plasmodium malariae
(D) Plasmodium ovale
(E) Plasmodium vivax

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Correct Answer: (B) Plasmodium falciparum

Plasmodium falciparumparasite is responsible for causing malaria. It is spread by the Anopheles mosquito. Diagnosis of P. falciparum infection is made through a blood smear. The only species of Plasmodium that causes cerebral malaria is P. falciparum.

Answer A is incorrect. Babesia microti is a protozoan transmitted by the deer ticks that carry Lyme disease and granulocytic ehrlichiosis. Babesiae parasitize RBCs and cause fever and hemolytic anemia. The symptoms are mild except in debilitated or splenectomized individuals, who develop severe parasitemias. In blood smears, Babesia resembles P. falciparum ring stages. They form characteristic tetrads (Maltese cross), which are diagnostic. In fatal cases, findings are related to shock and hypoxia and include jaundice, hepatic necrosis, acute renal tubular necrosis, acute respiratory distress syndrome, hemolysis, and hemorrhages but no cerebral involvement.

Answer C is incorrect. Plasmodium malariae infection has a 72-hour cyclic fever. P. malariae, however, does not cause cerebral malaria.

Answer D is incorrect. Plasmodium ovale infection has a 48-hour cyclic fever. A unique feature of P. vivax and P. ovale organisms is that they can form hypnozoites that can remain dormant in the liver for long periods, only to resurface later. However, P. ovale does not cause cerebral malaria.

Answer E is incorrect. Plasmodium vivax infection has a 48-hour cyclic fever. A unique feature of both P. vivax and P. ovale organisms is that they can form hypnozoites that can remain dormant in the liver for long periods, only to resurface later. However, P. vivax does not cause cerebral malaria.
answered Mar 28, 2017 by Rajesh Bahara

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