A Cluster of Plasmodium ovale Infections in Belgian Military Personnel after Deployment in Kindu, Democratic Republic of Congo: A Retrospective Study

Abstract

Plasmodium ovale malaria is often neglected due to its less severe course compared to Plasmodium falciparum. In 2011–2012, Belgian Armed Forces identified a cluster of P. ovale cases among military personnel after deployment in the Democratic Republic of Congo (DRC). In this retrospective, monocentric, observational study, clinical and biological features of soldiers diagnosed with P. ovale after deployment in DRC were reviewed. Species diagnosis was based on polymerase chain reaction (PCR) and/or thick blood smear. Medical records of 149 soldiers screened at the Queen Astrid Military Hospital after deployment were reviewed. Eight cases (seven P. ovale infections and one P. ovale—falciparum coinfection) were identified. All had positive thick smears, and seven were confirmed by PCR. Chemoprophylaxis was mefloquine in all subjects. Median time of disease onset was 101 days after return from the endemic region. Median delay between return and diagnosis was 103 days. All P. ovale bouts were uncomplicated. None had relapses after primaquine treatment. This military cohort highlights a hotspot of P. ovale in Eastern DRC. Non-specific symptoms, the less severe presentation, the lack of sensitive parasitological tools in the field and long delays between infection and symptoms probably lead to underestimation of P. ovale cases.

Prevalence of non-Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo

“…Even with appropriate treatment, chronic sub-clinical P. malariae infection can occur because of its extended pre-patent period when inadequate drug levels in the blood cannot eliminate newly emerging merozoites [ 41 , 42 ]. Plasmodium ovale is responsible for malaria relapses, even after months or even years without the person showing symptoms, due to the presence of hypnozoites [ 11 , 12 ]. In the present study, the urban setting was revealed as a zone of higher perennial sub-microscopic infection, compared to the rural area where the non- P. falciparum species were more pronounced during the dry season.…”

“…Plasmodium ovale infection represents < 1% of all malaria infections worldwide [ 9 , 10 ]. Despite its low prevalence, however, P. ovale infections are directly linked to the danger of relapses after months or even years due to the presence of hypnozoites [ 11 , 12 ], which may cause severe disease and even death [ 13 ]. The global distribution of Plasmodium malariae is sparse and variable, but frequently co-endemic with P. falciparum [ 14 , 15 ].…”

Infection Prevention and Control: Practical and Educational Advances

“…A cluster of eight Plasmodium ovale infections among Belgian military personnel was recorded after deployment in the Democratic Republic of Congo, with a median delay between return from deployment and diagnosis of 103 (IQR 62-339) days, indicating that non-specific symptoms and lack of sensitive diagnostic tools in the field might have led to underestimation of infection [ 20 ].…”