High Prevalence of Asymptomatic Plasmodium falciparum Infection in Gabonese Adults

Abstract

Plasmodium falciparum, the most common malarial parasite in sub-Saharan Africa, accounts for a high number of deaths in children less than five years of age. In malaria-endemic countries with stable transmission, semi-immunity is usually acquired after childhood. For adults, severe malaria is rare. Infected adults have either uncomplicated malaria or asymptomatic parasitemia. During a period of one year, we screened 497 afebrile males to investigate the prevalence of asymptomatic P. falciparum parasitemia in villages near Lambaréné, Gabon by use of three different methods. A total of 52% of the individuals had parasites detected by a subtelomeric variable open reading frame polymerase chain reaction (stevor-PCR), 27% of the rapid diagnostic test results were positive, and 12% of the thick blood smears with low parasitemias had P. falciparum. Most positive cases were only detected by the stevor-PCR. Asymptomatic P. falciparum parasitemia in adults living in a malaria-endemic country is frequent.

Evidence-based clinical guidelines for immigrants and refugees

“…Initial searches for documents about screening for malaria in immigrants and refugees generated many retrospective and prospective reviews of screening in asymptomatic migrants, several of which related to refugees. [358][359][360][361] Some of these articles provided recommendations on screening for malaria in migrants from areas where the disease is endemic; however, none reported use of a systematic review methodology. We found no randomized controlled trials investigating the effect of routine screening of asymptomatic individuals on morbidity and mortality related to malaria.…”

“…324,352,[358][359][360]364,365 A limited number of follow-up studies suggest that the risk of development of symptomatic malaria after screening is 20% to 40%. [358][359][360]365 The burden of symptomatic malaria among Canadian migrants is difficult to ascertain. The Public Health Agency of Canada receives reports of 350 to 1000 imported malaria cases per year, but the reason for travel in these cases is not reported.…”

Comparison of diagnostics for the detection of asymptomatic Plasmodium falciparum infections to inform control and elimination strategies

“…In total, 20 RDT: microscopy studies and 13 RDT:PCR studies from the literature search met our inclusion criteria. Combined with additional data sets from DHS and unpublished studies, the pooled data available for evaluation yielded 323 pairs of prevalence estimates for RDT and microscopy 5,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][44][45][46][47][48][49] and 162 pairs for RDT and PCR 25,27,34,39,40,42,[45][46][47][48][49][50][51][52][53][54][55] . The extracted proportions together with the main characteristics of the studies from our literature search are provided in the Supplementary Information.…”

“…Where available, information on location, sample size, RDT brand and type (HRP2 or pLDH), age group (15 or younger compared with older than 15) and prevalence estimates were recorded 5,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] . Furthermore, data from the DHS online database were extracted 43 .…”

“…Of the contacted authors, six responded within the timeframe; five data sets were included [45][46][47]49,50 , and one data set had been destroyed for privacy compliance. Prevalence measures and study information (including PCR method) were extracted as described above from the publications in the aforementioned literature search and the non-responders group, as well as included studies from the RDT and microscopy search that also reported PCR proportions 25,27,34,39,40,42,[51][52][53][54][55] . Four additional individual-level unpublished and published data sets were included 44,48 .…”