Malaria remains a rare but serious complication of transfusion because of the asymptomatic persistence of parasites in some donors. In nonendemic countries, the predominant strategy of deferral or cellular component discard from "risk" donors is effective in minimizing the incidence but is wasteful. In endemic countries where recipients are commonly immune, transfusion strategies focus on chemoprophylaxis for the donor and recipient or ensure that blood collected in highly endemic regions is not transfused to patients from areas of low endemicity. Donors implicated in transfusion-transmitted malaria are predominantly "semi-immune" with very low parasite loads. Their detection by even the most sensitive antigen or polymerase chain reaction (PCR) assays cannot be guaranteed and, in a number of cases, is unlikely because the infectious dose is estimated to be 1 to 10 parasites in a unit of blood. Retrospective analysis of implicated donors has confirmed the presence of high titer antibodies in such individuals. In regions of low immunity, serological assays offer an efficient method to identify such infectious donors. The recent development of enzyme immunoassays (EIAs) with improved sensitivity to Plasmodium falciparum and Plasmodium vivax , the predominant transfusion threats, has heightened the appeal of serological testing. Although universal serological screening in nonendemic regions is not cost-effective, targeted screening of donors identified at risk by travel-based questioning can significantly reduce wastage through reinstatement. Importantly, transfusion safety does not appear to be compromised by this approach as evidenced by the lack of a documented transmission in France between 1983 and September 2002, where such a strategy has been used since 1976. The development of automated protein microarray-based technology has the potential to further enhance antibody/antigen sensitivity; however, its application to donor screening is likely to be some years off. There is also the potential that pathogen inactivation techniques currently under development to address the bacterial contamination of blood components may also be effective against malaria parasites to make malarial testing redundant or at least reduce its cost/benefit ratio. Nonetheless, there are still significant problems to be solved in respect of validating and licensing these systems. Assuming that they are successfully marketed, their high cost may also impact their cost-effectiveness in comparison with targeted malaria testing strategies already in place in some jurisdictions.
"have implemented malaria antibody screening such that only individuals who are known to have been exposed to organisms causing malaria are subject to deferral of donations rather than all donors who have traveled to or lived in regions where malaria is endemic. Commercial antibody enzyme-linked immunosorbent assays (ELISAs) are currently in use in some countries like the United Kingdom, France, and Australia, and reinstatement of questionnairedeferred donors was discussed in Canada and the United States   . In these cases, blood donors are tested for antibodies directed against Plasmodium-derived antigens within several months of deferral; when the tested individuals show negative antibody results, donation is allowed. "
[Show abstract][Hide abstract] ABSTRACT: Background: Rapid diagnostic tests for malaria are now a commonly used procedure for malaria diagnosis. Despite some problems related to sensitivity and applicability, malaria rapid diagnostic tests (RDTs), are currently considered the best option to overcome well trained experts in blood banks and fast releas of blood units. Objectives: To detect malarial parasites using OptiMAL IT rapid test and to compare this method with the peripheral blood smear (PBS) and polymerase chain reaction (PCR) methods. Methods: Blood samples were collected from 100 patients clinically confirmed of having malaria and from 6698 random healthy blood donor volunteers. These samples were used to perform PBS examination, the OptiMAL test and PCR by standard protocols. Results: PBS examination found malarial parasites in 100 (100%) patients samples with a parasite load more than 0.01% and negative for all samples of blood donor volunteers. Positive samples obtained in PBS were also positive by OptiMAL test without differentiating between mixed infection. PCR could detect P. falciparum in 100 (100%) patients samples and two (2%) were positive for P. vivax in addition to P. falciparum. Conclusions: OptiMAL IT rapid diagnostic test can replace the peripheral blood smear method in blood banks with taking into consideration the limit of kit parasite load detectability. PCR is the most sensitive method that can detect low parasitaemia and mixed infection.
"Immunofluorescence detection of malaria antibodies was until recently the gold standard
, but is unsuitable for high-throughput screening. ELISA-based seroprevalence screening is a potentially useful epidemiological tool
. An immuno-enzymatic assay combining the crude P. falciparum antigen and recombinant P. vivax proteins was already developed, exhibiting high specificity and analytical sensitivity (96.7 and 93.1%, respectively) in the detection of Plasmodium antibodies
[Show abstract][Hide abstract] ABSTRACT: Background
Malaria Is A Life-Threatening Pathology In Africa. Plasmodium Falciparum And Plasmodium Vivax Attract The Most Focus Because Of Their High Prevalence And Mortality. Knowledge About The Prevalence Of The Cryptic Pathogens Plasmodium Ovale And Plasmodium Malariae Is Limited. Thanks To Recombinant Tools, Their Seroprevalence Was Measured For The First Time, As Well As The Prevalence Of Mixed Infections In A Malaria-Asymptomatic Population In Benin, A Malaria-Endemic Country.
A Panel Of 1,235 Blood Donations Collected Over Ten Months In Benin Was Used For Validation Of The Recombinant Tools. Recombinant P. Falciparum, P. Malariae, P. Ovale MSP1, And P. Falciparum AMA1 Were Engineered And Validated On A Biobank With Malaria-Infected Patients (N = 144) Using A Species-Speific ELISA Test (Recelisa). Results Were Compared To An ELISA Using A Native P. Falciparum Antigen (NatELISA).
Among Microscopically Negative African Blood Donors, 85% (1,050/1,235) Present Antibodies Directed To Native P. Falciparum, 94.4% (1,166/1,235) To rPfMSP1 And rPfAMA1, 56.8% (702/1,235) To rPoMSP1, 67.5% (834/1235) To rPmMSP1 And 45.3% Of The Malaria Seropositive Population Had Antibodies Recognizing The Three Species.
A High Rate Of Antibodies Against P. Ovale And P. Malariae Was Found In Asymptomatic Blood Donors. The Proportion Of Mixed Infections Involving Three Species Was Also Unexpected. These Data Suggest That Determining Seroprevalence For These Cryptic Species Is An Appropriate Tool To Estimate Their Incidence, At The Eve Of Upcoming Anti-P. Falciparum Vaccination Campaigns.
"Transfusion-transmitted Plasmodium parasites represent an important risk factor because they can cause severe malaria with a high fatality rate . The chronic infection can persist in humans for a long period of time: up to two years or more for P. falciparum, up to seven years for P. vivax, and even for an entire lifetime for P. malariae. "
[Show abstract][Hide abstract] ABSTRACT: In Brazil, malaria is endemic in the Amazon River basin and non-endemic in the extra-Amazon region, which includes areas of São Paulo state. In this state, a number of autochthonous cases of malaria occur annually, and the prevalence of subclinical infection is unknown. Asymptomatic infections may remain undetected, maintaining transmission of the pathogen, including by blood transfusion. In these report it has been described subclinical Plasmodium infection in blood donors from a blood transfusion centre in São Paulo, Brazil.
In this cross-sectional study, representative samples of blood were obtained from 1,108 healthy blood donors at the Fundação Pró-Sangue Hemocentro de São Paulo, the main blood transfusion centre in São Paulo. Malaria exposure was defined by the home region (exposed: forest region; non-exposed: non-forest region). Real-time PCR was used to detect Plasmodium falciparum and Plasmodium vivax. Subclinical malaria cases were geo-referenced.
Eighty-four (7.41%) blood donors tested positive for Plasmodium; 57 of these were infected by P. falciparum, 25 by P. vivax, and 2 by both. The prevalence of P. falciparum and P. vivax was 5.14 and 2.26, respectively. The overall prevalence ratio (PR) was 3.23 (95% confidence interval (CI) 2.03, 5.13); P. falciparum PR was 16.11 (95% CI 5.87, 44.21) and P. vivax PR was 0.47 (95% CI 0.2, 1.12). Plasmodium falciparum subclinical malaria infection in the Atlantic Forest domain was present in the mountain regions while P. vivax infection was observed in cities from forest-surrounded areas.
The presence of Plasmodium in healthy blood donors from a region known as non-endemic, which is important in the context of transfusion biosafety, was described. Infected recipients may become asymptomatic carriers and a reservoir for parasites, maintaining their transmission. Furthermore, P. falciparum PR was positively associated with the forest environment, and P. vivax was associated with forest fragmentation.
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