An 8-year survey on the occurrence of imported malaria in a nonendemic area by microscopy and molecular assays.

Our study aimed to describe the occurrence of imported malaria in a nonendemic area (Parma, Italy) during the period 2000 to 2007, comparing the data obtained by microscopy and molecular assays targeting plasmodial 18S subunit rRNA gene. The prevalence of imported malaria in Parma was 21.8% by microscopy and 22.7% by polymerase chain reaction (PCR). Plasmodium falciparum accounted for 81.1% of the cases, followed by Plasmodium ovale (8.8%), Plasmodium vivax (3.8%), and Plasmodium malariae (1.9%). Mixed infections accounted for 4.4% of the cases. In this study, PCRs proved to be more sensitive and specific than microscopy and changed the picture of malaria epidemiology in Parma, detecting additional cases of malaria undiagnosed by microscopy and allowing speciation of plasmodia in cases misidentified by microscopy. Generally, imported malaria cases reflect the number of immigrants who visit their native countries, in particular, West Africa, explaining the increased prevalence of P. ovale cases among non-P. falciparum infections in Parma.