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1998 Presentations for the Poster and Vignette Sessions
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LATE RELAPSE OF MALARIA. Prasad G.A., Gennis M.A., University of Wisconsin Medical School, Milwaukee Clinical Campus, Sinai Samaritan Medical Center, Milwaukee,WI.

A forty six year old Asian Indian male presented to the Emergency Department with history of fever for the past four days. The fever was intermittent, was associated with chills and rigors, myalgias and generalized headaches. There were no other localizing symptoms. Past medical history was significant for previous episodes of Malaria and Enteric Fever, treated with Chloroquine and Ciprofloxacin respectively. There was no history of treatment with Primaquine. The last episode of malaria was one year ago and the patient was in the United States for about 11 months. There was no other significant travel history. On examination, the patient was febrile, toxic and dehydrated. There were no other findings on examination.Laboratory evaluation was significant for mild normochromic normocytic anemia(11/32), normal reticulocyte count, thrombocytopenia(54,000), hyperbilirubinemia(3.3),and low Haptoglobin(34). The peripheral smear was positive for trophozoites and schizonts of Plasmodium vivax. The patient was treated with oral Chloroquine and subsequently with Primaquine to effect radical cure. The patient defervesced rapidly and has an uneventful hospital course. He remains asymptomatic at a three month followup.

Malaria is caused by a protozoan parasite of the genus Plasmodium. Two of the four species causing human infection,P.vivax and P.ovale, cause recurrent disease by relapsing infection. The life cycle of all Plasmodium species is initiated when the sporozoites inoculated by the mosquito reach the hepatocytes and start preerythrocytic schizogony. This results in release of merozoites which infect erythrocytes and complete the asexual phase of the lifecycle. The paroxysms of fever and chills are produced by the intravascular hemolysis caused by the release of merozoites from red blood cells, also leading to anemia and hyperbilirubinemia. Thrombocytopenia is seen in 50-80% of patients with malaria. It is now known that some of the sporozoites initially inoculated by the mosquito do not begin asexual reproduction but remain dormant as Hypnozoites in hepatocytes. Studies quote a relapse rate of 25-30% in endemic areas after proper treatment. Relapse is usually seen within 2-3 months(early)especially in endemic areas.Relapse after 3 months(late) is uncommon. 4-Aminoquinolines like Chloroquine are effective in destruction of the erythrocytic phase but do not effect the Hypnozoites. This explains the multiple relapses seen in this patient who had been treated with Chloroquine but not with Primaquine, which is effective in eradicating the hynozoites and preventing relapse in 90% of cases.

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