[Prevalence of Plasmodium spp. in asymptomatic African immigrants assessed by nucleic acid sequence based...

Malaria is one of the most important infectious diseases in the world. Although most cases occur in the tropical regions of Africa, Asia, Central and South America, there is in Europe a significant increase in the number of imported cases in non-endemic countries, in particular due to the higher mobility in today's society. The prevalence of a possible asymptomatic infection with Plasmodium species was assessed using Nucleic Acid Sequence Based Amplification (NASBA) assays on clinical samples collected from 195 study cases with no clinical signs related to malaria and coming from sub-Saharan Africa. In addition, base-line demographic, clinical and socio-economic information was collected from study participants who also underwent a full clinical examination. Sixty-two study subjects (31.8%) were found positive for Plasmodium using a pan Plasmodium specific NASBA based on the small subunit 18S rRNA gene (18S NASBA). Twenty-four samples (38%) of the 62 positive study cases were found positive with a Pfs25 mRNA NASBA, which specifically detects gametocytes of Plasmodium falciparum. This study showed that a substantial proportion of people originating from malaria endemic countries harbour malaria parasites in their blood. If transmission conditions are available, they could be a reservoir.