A Case of Rare Imported Plasmodium ovale Infection in Shaoxing

Malaria is a global disease caused by the transmission of the malaria parasite through the bites of infected Anopheles mosquitoes. There are 4 kinds of common malaria parasites, among which oval malaria is mainly prevalent in tropical West Africa, with a narrow distribution range, mainly imported cases in China, which is relatively rare. Because the morphology, attack cycle, recrudescence and relapse are similar to those of Plasmodium vivax and, therefore, is easily missed and misdiagnosed.

Malaria parasite-specific antigens were detected in whole blood samples using rapid diagnostic tests (RDT). Peripheral blood was used to prepare thick and thin smears, which were then stained with Giemsa for the identification of malaria parasites and different parasite morphologies under an oil microscope. Plasmodium species were identified using fluorescence quantitative PCR.

The patient's RDT revealed two red response lines (only T2 positive), indicating a single or mixed infection of three types of malaria (Plasmodium vivax, Plasmodium malarie, Plasmodium ovale) excluding Plasmodium falciparum. Thick smears exhibited various stages of Plasmodium such as hypertrophic rings and gametocytes, while thin films displayed Plasmodium trophozoites, gametocytes, etc., resembling oval malaria. The patients were diagnosed with Plasmodium ovum infection through fluorescence quantitative PCR, and targeted treatment was administered.

The incidence of Plasmodium ovum infection is low, and there is a risk of overlooking or misdiagnosing the infection in laboratory tests. It is essential for laboratory staff to enhance their morphological recognition skills for Plasmodium and to integrate blood routine analysis, RDT, and PCR results in order to facilitate early diagnosis and prompt treatment.