A case of an asymptomatic Plasmodium falciparum infection followed by a symptomatic Plasmodium ovale infection in a soldier deployed to South Sudan

Abstract

Background: Asymptomatic malaria poses a significant challenge to malaria eradication efforts and delays global elimination strategies. Mixed infections are also a major concern, as they frequently relapse, increase the risk of severe malaria, require more accurate diagnosis for appropriate treatment, and contribute to the development of drug resistance.

Case presentation: A 25-year-old soldier was diagnosed with malaria following deployment in South Sudan. A comprehensive survey identified an asymptomatic Plasmodium falciparum infection, confirmed by peripheral blood smear and polymerase chain reaction (PCR). Despite being discharged after treatment, the patient developed fever and other symptoms one month later. Subsequent laboratory tests confirmed Plasmodium ovale infection based on peripheral blood smears and PCR.

Conclusion: This case underscores the importance of molecular detection for surveillance and vigilant follow-up in malaria management, particularly among patients with a history of deployment in endemic regions. The detection of P. ovale after treatment for P. falciparum highlights the need for increased awareness and testing for mixed infections to ensure effective malaria control strategies.

Keywords: Plasmodium falciparum; Plasmodium ovale; Asymptomatic infection; Malaria; South Sudan.

Fig. 1

A. Peripheral blood smear of a 25-year-old soldier on March 23, 2023, during the first hospitalization. The smear shows low parasitemia with one infected red blood cell per 100 high-power fields, along with a single “banana-shaped” gametocyte. B. Peripheral blood smear from the same soldier on May 8, 2023, during the second hospitalization. The smear reveals numerous non-P. falciparum gametocytes, indicating a symptomatic P. ovale infection. C. Phylogenetic tree based on the partial 18S rRNA sequence (875 bp) of Plasmodium species. The tree was constructed using the CLUSTAL X software (http://www.clustal.org/clustal2/) with the neighbor-joining method and 1000 bootstrap replicates.