P lasmodium genome in blood donors at risk for malaria after several years of residence in I taly

Background At present, the main risk of transfusion‐transmitted malaria ( TTM ) in nonendemic countries is chronic, asymptomatic immigrants from malaria‐endemic areas. Semi‐immune donors may carry undetected parasitemia. This study examines P lasmodium infection in at‐risk blood donors in N orthern I taly. Study Design and Methods Plasma samples from 97 candidate donors and 80 controls were tested for malarial antibodies using a commercial enzyme immunoassay. The conserved 18 S rRNA and the mitochondrial genes of P lasmodium were amplified to detect and quantify parasite genomes (copies/ mL ). P lasmodium species were identified with a species‐specific nested polymerase chain reaction. Parasitemic samples were further tested by amplification of polymorphic repetitive regions in MSP ‐1 B lock 2, MSP ‐2 B lock 3, and glutamate‐rich protein ( GLURP ) confirmed by sequencing. Results Three of 83 seropositive (3.6%) and one of 14 seronegative at‐risk candidate donors carried P lasmodium genome (4 × 10 3 ‐8.5 × 10 4 copies/ mL ): two P . falciparum , one P . malariae (seronegative sample), and one coinfection with P . malariae and P . ovale . Alleles of MSP ‐1 ( MAD 20 and K 1), MSP ‐2 (3 D 7 and FC 27), and GLURP were amplified from S ample 261. In S ample 282 only one allele in MSP ‐2 ( FC 27) and GLURP was amplified. No alleles were detected in S amples 283 and 331. Conclusions Immigrants from endemic countries might carry infectious P lasmodium after 2 to 5 years of continuous residence in I taly. Serologic screening may miss donors carrying P . malariae . Permanent exclusion or screening for both antibodies and genome are needed to prevent TTM .