RESUMO
After hepatitis and AIDS, malaria is the most prevalent transfusion outcome in endemic areas. Presence of asymptomatic carriess of malaria parasites in the endemic areas can be a source of infection in transmission of malaria by blood transfusion. Prevention of malaria caused by blood transfusion depends on screening blood donors and deleting infected blood samples. To screen blood samples, parasitological, serologic and molecular methods have been applied. In this study 120 blood donors in Iranshahr in Sistan-Baloochestan province were tested with different methods of thick and thin blood films, Immuno-Fluorescent Antibody Test [IFAT], and Polymerase Chain Reaction [PCR]. The result of all thick and thin blood films were negative. IFAT by using P.vivax antigen and P.falciparum antigen for 38 and 6 donors respectively showed a titre of antibody equal to +/- 1/20-1/320 [17 of the former group and 4 of the latter had a history of malaria infection]. The PCR assay using silica for DNA extraction and using P .falciparum specified primers with sensitivity rate equal to 2-3 parasites per microlitre of blood was negative for all subjects under study. This study showed, although microscopic examination of blood smears was inexpensive and simple, but it is labor-intensive and time-consuming that makes it insensitive for detection of low-level parasitemia in asymptomatic donors and for screening a large number of specimen. IFAT would not always show the real existence of parasites and in spite of simplicity and sensitivity because of its disability to be automated is not suitable for screening a large number of specimen. On the other hand, IF AT in individuals with malaria history and absence of parasites in their blood may be positive for a long period. It was approved that molecular methods such as PCR were more sensitive and more specific than conventional microscopic examination and their great advantage was the ability to detect the infection with low-level parasitemia that may have been distinguished by blood films examination. In the present study, probably because of low number of specimen or limited study duration with PCR method, or probably since parasitemia exiting in the subjects under study was less than 2-3 parasites per microlitre of blood, we were not able to detect positive cases