Molecular screening of Plasmodium sp. asymptomatic carriers among transfusion centers from Brazilian Amazon region

Abstract

SUMMARYThe transmission of malaria in Brazil is heterogeneous throughout endemic areas and the presence of asymptomatic Plasmodium sp. carriers (APCs) in the Brazilian Amazon has already been demonstrated. Malaria screening in blood banks is based on the selection of donors in respect to possible risks associated with travel or residence, clinical evidence and/or inaccurate diagnostic methods thereby increasing the probability of transfusion-transmitted infection. We evaluated the frequency of APCs in four blood services in distinct areas of the Brazilian Amazon region. DNA was obtained from 400 human blood samples for testing using the phenol-chloroform method followed by a nested-PCR protocol with species-specific primers. The positivity rate varied from 1 to 3% of blood donors from the four areas with an average of 2.3%. All positive individuals had mixed infections for Plasmodium vivax and Plasmodium falciparum. No significant differences in the results were detected among these areas; the majority of cases originated from the transfusion centres of Porto Velho, Rondônia State and Macapá, Amapá State. Although it is still unclear whether APC individuals may act as reservoirs of the parasite, efficient screening of APCs and malaria patients in Brazilian blood services from endemic areas needs to be improved.

Detection of Plasmodium falciparum and Plasmodium vivax subclinical infection in non-endemic region: implications for blood transfusion and malaria epidemiology

“…Plasmodium transmission by transfusion usually occurs through whole blood and red blood cells and may occur less frequently through platelet concentrates, white blood cells, cryoprecipitate, and fresh frozen plasma [18,45]. The blood bank is therefore an important target for controlling undesirable Plasmodium transmission in endemic [38,46] and non-endemic regions [43,47]. …”

Diagnóstico molecular da malária em uma unidade de atenção terciária na Amazônia Brasileira

“…A alta co-positividade da PCR com a gota espessa na detecção de infecção malárica reforça sua utilidade em estudos epidemiológicos de prevalência, estudos de eficácia terapêutica e vacinal, detecção de portadores assintomáticos de plasmódio e na avaliação de novos métodos diagnósticos para malária 10 15 21 . Em bancos de sangue, o emprego da PCR pode ser de suma importância para o controle da malária transfusional 8 . Finalmente, o uso da PCR em unidades de referência pode ter alguma utilidade na avaliação do desempenho de microscopistas considerados experientes 6 .…”

Unexpected detection of Plasmodium vivax and Plasmodium falciparum DNA in asymptomatic blood donors: fact or artifact?

“…So far there are only two published studies investigating Plasmodium prevalence by molecular methods among Brazilian blood donors [12, 13], both performed in the endemic area (the Amazon) and cited in the paper of Maselli et al [1]. The former described a 2.3% prevalence of P. vivax  +  P. falciparum infections, while the latter detected 1.34%.…”