A case of imported Plasmodium malariae malaria

Abstract

Malaria, the most common vector-borne parasite infection worldwide, results from infection by Plasmodium species. Approximately 80% of malaria cases are caused by P. vivax, which is broadly distributed from tropical to temperate regions; P. falciparum is the second most common infectious species. P. malariae and P. ovale are responsible for a relatively small proportion of malaria cases. Here, we report the case of a 23-yr-old Korean woman who acquired a P. malariae infection while visiting the Republic of Ghana in West Africa for business. She was diagnosed with P. malariae malaria on the basis of peripheral blood smear (PBS) and species-specific conventional and real-time PCR assays for 18S rRNA. She was treated with hydroxychloroquine, and the resulting PBS examination on day 2 suggested that negative conversion occurred. At her 1-month follow-up, however, both the PBS examination and molecular test for malaria demonstrated recurrent parasitemia. We started rescue therapy with mefloquine, and the patient recovered successfully. This is an important finding suggesting possible late recrudescence of a chloroquine-resistant P. malariae strain identified not only by its morphological features, but also by molecular tests.

Keywords: 18S rRNA conventional PCR; 18S rRNA real-time PCR; Chloroquine resistance; Late recrudescence; Malaria; Plasmodium malariae.

Fig. 1

Peripheral blood at the time of presentation (A, B, C) and at the 1-month follow-up showing a few parasites (D, E) by Wright-Giemsa staining (×1,000). (A) Amoeboid form of a mature trophozoite; (B) an early schizont in a contracted cell; (C) a late schizont with 8 merozoites and central coarse dark pigment; (D) angular form of a mature trophozoite; (E) a late schizont with symmetrically arranged merozoites.

Fig. 2

Conventional PCR results for Plasmodium species-specific 18S rRNA. A 144-bp fragment corresponding to P. malariae was detected from the PCR-amplified product of the patient's blood sample. M: DNA size marker. Abbreviations: DW, distilled water; NC, negative control; PC, positive control; Pt, the patient.

Fig. 3

Amplification plots and melting curve analyses of the 4 Plasmodium species-specific 18S rRNA real-time PCR assays showing the presence of P. malariae. Positive results were obtained only for P. malariae (A). Three consecutive analyses of Plasmodium malariae-specific real-time PCR were performed, showing persistent positivity at the 1-month follow-up (2011.09.28) and then final negative conversion (2011.10.04) (B). The melting temperature (T_m) for P. malariae was approximately 76.36-76.86℃. Abbreviations: Pt, the patient; DW, distilled water; PC, positive control.