三日熱マラリアの再発との判別が困難であった4ヵ月以上の潜伏期間の後に発症した四日熱マラリアの1例 [in Japanese] Plasmodium malariae Malaria with more than a 4-month Incubation Period : Difficult to Distinguish from a Relapse of Plasmodium vivax Malaria [in Japanese]
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We report herein on a case of <i>Plasmodium malariae</i> malaria with more than a 4-month incubation period. A 35-year-old Japanese man who first presented to our clinic with fever and history of travel to Papua New Guinea was suspected of having <i>Plasmodium vivax</i> malaria based on peripheral smear results. We admitted him and initiated treatment with mefloquine. After two days of therapy, he became afebrile. We discharged him, and <i>P. vivax</i> was later confirmed with PCR. We started mefloquine prophylaxis for a planned trip to Papua New Guinea. After his return, a standard dose of primaquine (15mg×14 days) was prescribed for a radical cure of <i>P. vivax</i>. About 4 months after his last visit to Papua New Guinea, he returned to our clinic with fever. We suspected a relapse of <i>P. vivax</i> malaria and admitted him for a second time. After two days of mefloquine therapy, his symptoms improved. We discharged him and restarted a higher dose of primaquine (30mg×14 days) therapy for a radical cure of <i>P. vivax</i>. Subsequently, the PCR test revealed the parasite was <i>P. malariae</i> and not <i>P. vivax</i>. Only 13 cases of <i>Plasmodium malariae</i> malaria have been reported in Japan during the past 10 years. Blood-stage schizonticides such as mefloquine is not active against the liver stage. Therefore, the use of these drugs for prophylaxis will not be effective for prevention of malaria if its liver stage is longer than the duration of effective chemoprophylaxis. Although the incubation period of <i>P. malariae</i> is typically 13 to 28 days, it occasionally lasts for months or even years. Careful attention should be given to the possibility that <i>P.malariae</i> occasionally has a long incubation period even in the absence of the hypnozoite stage.
- Kansenshogaku Zasshi
Kansenshogaku Zasshi 87(4), 446-450, 2013-07-20
The Japanese Association for Infectious Diseases